Patent Publication Number: US-2023152911-A1

Title: Electrostatic discharge protection of a power efficient stylus for an electronic device

Description:
FIELD 
     This generally relates to a stylus and, more particularly, to a power efficient stylus for an electronic device, and, more particularly, to such a stylus with electrostatic discharge protection, as well as to systems, methods, and computer-readable media for use thereof. 
     BACKGROUND 
     Some systems may include an electronic device with a sensor assembly to facilitate a user&#39;s interaction with the device, as well as a stylus for providing a user with a more precise instrument than the user&#39;s fingers for interacting with the sensor assembly, such as for generating a graphical object on a display of the electronic device. However, existing systems often require an active stylus that uses power intensive electronics or a passive stylus that is difficult to distinguish from a user&#39;s finger. 
     SUMMARY 
     Systems, methods, and computer-readable media for enabling a power efficient stylus with electrostatic discharge protection for an electronic device are provided. 
     As an example, a stylus for use with an electronic device that includes an input component with an input surface may be provided, the stylus including a housing and stylus circuitry at least partially positioned within the housing, wherein the stylus circuitry includes body circuitry, a front tip interface component, and front tip stylus circuitry positioned between and electrically coupled to each one of the body circuitry and the front tip interface component, the front tip stylus circuitry includes non-linear circuitry that is operative to provide a non-linear load between the body circuitry and the front tip interface component when the stylus circuitry is stimulated by an external stimulation, and the non-linear load is operative to provide a stylus electric field that is detectable by the electronic device when the front tip interface component of the stylus is positioned adjacent the input surface of the input component of the electronic device. 
     As another example, a stylus for use with an electronic device that includes an input component with an input surface may be provided, the stylus including a tip interface component and tip stylus circuitry electrically coupled to the tip interface component, wherein the stylus is operative to drive a current back and forth through the tip stylus circuitry when the tip stylus circuitry is stimulated by an electrical signal provided by the input component of the electronic device, and the driven current is operative to provide a modulated version of the electrical signal that is detectable by the electronic device when the tip interface component of the stylus is positioned adjacent the input surface of the input component of the electronic device. 
     As yet another example, a method for using a stylus including non-linear circuitry at an input component of an electronic device may be provided, the method including transmitting an electrical signal from transmitter circuitry of the input component of the electronic device, stimulating the non-linear circuitry of the stylus with the transmitted electrical signal, providing a non-linear load at the stylus based on the stimulating, and creating a harmonic of the transmitted electrical signal at the input component of the electronic device based on the provided non-linear load. 
     As yet another example, a stylus for use with an electronic device that includes an input component with an input surface may be provided, the stylus including a housing and stylus circuitry at least partially positioned within the housing, wherein the stylus circuitry includes body circuitry, a tip interface component, and tip stylus circuitry, the tip stylus circuitry includes switch circuitry that is operative to alternate according to a pattern between a first state in which the body circuitry and the tip interface component are electrically coupled and a second state in which the body circuitry and the tip interface component are not electrically coupled, and the alternation of the switch circuitry is operative to provide a modulated capacitance at the tip interface component that is detectable by the electronic device when the tip interface component of the stylus is positioned adjacent the input surface of the input component of the electronic device. 
     As yet another example, a stylus for use with an electronic device that includes an input component with an input surface may be provided, the stylus including a tip interface component and tip stylus circuitry electrically coupled to the tip interface component, wherein the tip stylus circuitry is operative to change a load of the stylus according to a pattern when the tip stylus circuitry is exposed to an electrical signal provided by the input component of the electronic device, and the changed load is operative to provide a modulated version of the electrical signal that is detectable by the electronic device when the tip interface component of the stylus is positioned adjacent the input surface of the input component of the electronic device. 
     As yet another example, a method for using a stylus including switching circuitry at an input component of an electronic device may be provided, the method including transmitting an electrical signal from transmitter circuitry of the input component of the electronic device, concurrently with the transmitting, switching the switching circuitry according to a pattern, and, based on the switching, modulating the transmitted electrical signal according to the pattern. 
     As yet another example, a method for detecting an accessory on an input surface of an input component of an electronic device that includes a matrix of a plurality of transmit electrodes and a plurality of receive electrodes, may be provided, the method including transmitting a transmit signal on each transmit electrode of at least a subset of the plurality of transmit electrodes, sensing a receive signal on each receive electrode of at least a subset of the plurality of receive electrodes, extracting, from each sensed receive signal, data indicative of a non-linear aspect of the transmit signal, and estimating a position of the accessory on the input surface based on the extracted data. 
     As yet another example, an electronic device may be provided that includes an input component including an input surface and a matrix underneath the input surface including a plurality of transmit electrodes and a plurality of receive electrodes, and processing circuitry configured to transmit a transmit signal on each transmit electrode of at least a subset of the plurality of transmit electrodes, sense a receive signal on each receive electrode of at least a subset of the plurality of receive electrodes, extract, from each sensed receive signal, data indicative of a non-linear aspect of the transmit signal, and estimate a position of an accessory on the input surface based on the extracted data. 
     As yet another example, an electronic device input component may be provided that includes an input surface, a plurality of electrodes, and processing circuitry configured to provide a transmit waveform on each electrode of at least a subset of the plurality of electrodes, detect a receive waveform on each electrode of at least another subset of the plurality of electrodes, extract, from each detected receive waveform, data indicative of asymmetric distortion of the transmit waveform, and determine a location of an accessory on the input surface based on the extracted data. 
     As yet another example, an electronic device may be provided that includes an input component including an input surface and a matrix underneath the input surface including a plurality of transmit electrodes and a plurality of receive electrodes, and processing circuitry configured to transmit signals on transmit electrodes of at least a subset of the plurality of transmit electrodes, sense a receive signal on each receive electrode of at least a subset of the plurality of receive electrodes, extract, from the sensed receive signals, data indicative of a non-linear response to the transmit signals, and estimate a position of an accessory on the input surface based on the extracted data. 
     As yet another example, an electronic device input component may be provided that includes an input surface, a plurality of electrodes, and processing circuitry configured to provide transmit waveforms on electrodes of at least a subset of the plurality of electrodes, detect a receive waveform on each electrode of at least another subset of the plurality of electrodes, extract, from the detected receive waveforms, data indicative of a non-linear response to the transmit waveforms, and determine a location of an accessory on the input surface based on the extracted data. 
     As yet another example, a stylus for use with an electronic device that includes an input component with an input surface may be provided, the stylus including a housing and stylus circuitry at least partially positioned within the housing, wherein the stylus circuitry includes body circuitry, a tip interface component, and tip circuitry positioned between and electrically coupled to each one of the body circuitry and the tip interface component, and the tip circuitry includes non-linear circuitry that is operative to provide a non-linear load between the body circuitry and the tip interface component when the stylus is stimulated by an external stimulation and electrostatic discharge (“ESD”) circuitry that is operative to provide ESD protection to the non-linear circuitry, the ESD circuitry including ESD path circuitry electrically coupled in parallel to the non-linear circuitry and ESD resistance circuitry electrically coupled in series with the non-linear circuitry and in parallel to the ESD path circuitry. 
     As yet another example, a stylus for use with an electronic device that includes an input component with an input surface may be provided, the stylus including a housing and stylus circuitry at least partially positioned within the housing, wherein the stylus circuitry includes body circuitry including a body point portion, a tip interface component, tip circuitry operative to provide a load between the body circuitry and the tip interface component when the stylus is stimulated by an external stimulation, and a conductive pad electrically coupled to the tip circuitry, the housing includes a first housing, a second housing that is removably coupled to the first housing, and a cover provided over an opening of the first housing, the tip circuitry is at least partially positioned within a first housing space defined by the first housing, the conductive pad is at least partially positioned within the first housing space, the body circuitry is at least partially positioned within a second housing space defined by the second housing, and, when the second housing is coupled to the first housing, the body point portion of the body circuitry is operative to pass through the cover and press into the conductive pad. 
     As yet another example, a stylus for use with an electronic device that includes an input component with an input surface may be provided, the stylus including a housing and stylus circuitry at least partially positioned within the housing, wherein the stylus circuitry includes body circuitry, a tip interface component, and tip circuitry operative to provide a load between the body circuitry and the tip interface component when the stylus is stimulated by an external stimulation, the load is operative to provide a stylus electric field that is detectable by the electronic device when the tip interface component of the stylus is positioned adjacent the input surface of the input component of the electronic device, the tip interface component is shaped as a spherical cap with a hollow space, and at least a portion of the tip circuitry is positioned within the hollow space. 
     As yet another example, an accessory for use with an electronic device that includes an input component with an input surface may be provided, the accessory including an enclosure and accessory circuitry at least partially positioned within the enclosure, wherein the accessory circuitry includes body circuitry, a tip interface component, and tip circuitry positioned between and electrically coupled to each one of the body circuitry and the tip interface component, wherein the tip circuitry includes first circuitry that is operative to provide an asymmetric load between the body circuitry and the tip interface component when the accessory is stimulated by an external stimulation, and second circuitry that is operative to provide electrostatic discharge (“ESD”) protection to the first circuitry, and wherein the second circuitry includes ESD path circuitry electrically coupled in parallel to the first circuitry or ESD resistance circuitry electrically coupled in series with the first circuitry. 
     As yet another example, a replaceable tip of an accessory assembly that further includes body circuitry at least partially positioned within a body housing space defined by a body housing may be provided, the replaceable tip including a tip housing that is removably couplable to the body housing, tip circuitry that is at least partially positioned within a tip housing space defined by the tip housing, a tip interface component, and a cover provided over an opening of the first housing, wherein, prior to the tip housing ever being coupled to the body housing, the cover is operative to prevent an electrostatic discharge (“ESD”) event within the tip housing space, and, when the tip housing is coupled to the body housing, a portion of the body circuitry passes through the cover and into the tip housing space and the tip circuitry is operative to provide a load between the body circuitry and the tip interface component when the accessory is stimulated by an external stimulation. 
     This Summary is provided only to summarize some example embodiments, so as to provide a basic understanding of some aspects of the subject matter described in this document. Accordingly, it will be appreciated that the features described in this Summary are only examples and should not be construed to narrow the scope or spirit of the subject matter described herein in any way. Unless otherwise stated, features described in the context of one example may be combined or used with features described in the context of one or more other examples. Other features, aspects, and advantages of the subject matter described herein will become apparent from the following Detailed Description, Figures, and Claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The discussion below makes reference to the following drawings, in which like reference characters refer to like parts throughout, and in which: 
         FIG.  1    is a schematic view of an illustrative user input system including an electronic device and a power efficient stylus; 
         FIG.  1 A  is a perspective view of an exemplary power efficient stylus interacting with an input surface of an exemplary electronic device of the system of  FIG.  1   ; 
         FIG.  1 B  is a side view of a portion of the system of  FIGS.  1  and  1 A  with the stylus oriented normal to the input surface of the electronic device; 
         FIG.  1 C  is a front view of the system of  FIGS.  1 - 1 B  showing the stylus oriented at an azimuthal angle of the stylus relative to a horizontal axis of the plane of the input surface of the electronic device; 
         FIG.  1 D  is a bottom view of the system of  FIGS.  1 - 1 C  showing the stylus oriented at a polar angle of the stylus relative to the plane of the input surface of the electronic device; 
         FIG.  2    is a partially transparent, semi-schematic view of an illustrative portion of a stylus of the system of  FIGS.  1 - 1 D ; 
         FIG.  2 A  is a schematic view of a portion of the system using a portion of a stylus of  FIGS.  1 - 1 D and  2   ; 
         FIG.  2 B  is a circuit diagram of the portion of the system using the portion of the stylus of  FIGS.  1 - 2 A ; 
         FIG.  2 C  is a partially transparent, semi-schematic view of the stylus of  FIGS.  1 - 2 B ; 
         FIG.  2 D  is a schematic view of the portion of the system using another portion of the stylus of  FIGS.  1 - 2 C ; 
         FIG.  2 E  is a circuit diagram of the portion of the system using the other portion of the stylus of  FIGS.  1 - 2 D ; 
         FIG.  2 F  is a schematic view of another portion of the system using the portion of the stylus of  FIGS.  1 - 2 E ; 
         FIG.  2 G  is a circuit diagram of the other portion of the system using the portion of the stylus of  FIGS.  1 - 2 F ; 
         FIG.  3    is a partially transparent, semi-schematic view of an illustrative portion of another stylus of the system of  FIGS.  1 - 1 D ; 
         FIG.  3 A  is a schematic view of a portion of the system using a portion of the stylus of  FIGS.  1 - 1 D and  3   ; 
         FIG.  3 B  is a schematic view of another portion of the system using the portion of the stylus of  FIGS.  1 - 1 D,  3 , and  3 A ; 
         FIG.  3 C  is a circuit diagram of the other portion of the system using the portion of the stylus of  FIGS.  1 - 1 D and  3 - 3 B ; 
         FIG.  4    is a partially transparent, semi-schematic view of an illustrative portion of yet another stylus of the system of  FIGS.  1 - 1 D ; 
         FIG.  5    is a partially transparent, semi-schematic view of an illustrative portion of yet another accessory of the system of  FIGS.  1 - 1 D ; 
         FIG.  6    is a schematic view of a portion of the system using a portion of a stylus of  FIGS.  1 - 1 D ; 
         FIG.  6 A  is a schematic view of a portion of the system and a cross-sectional view of another portion of the system and stylus of  FIGS.  1 - 1 D and  6   ; 
         FIG.  6 B  is a plot over time of an exemplary voltage applied to a transmit electrode of the system of  FIGS.  1 - 1 D,  6 , and  6 A ; 
         FIG.  6 C  is a plot over time of an exemplary voltage provided by a tip of the stylus of the system of  FIGS.  1 - 1 D,  6 , and  6 A ; 
         FIG.  6 D  is a plot of an exemplary magnitude with respect to frequency of an applied voltage as sensed by a receive electrode of the system of  FIGS.  1 - 1 D,  6 , and  6 A ; 
         FIG.  6 E  is a first depiction of sensed external element(s) on a surface of the electronic device of the system of  FIGS.  1 - 1 D,  6 , and  6 A ; 
         FIG.  6 F  is a second depiction of sensed external element(s) on a surface of the electronic device of the system of  FIGS.  1 - 1 D,  6 , and  6 A ; 
         FIGS.  7 - 10    are flowcharts of illustrative processes for using a stylus; 
         FIGS.  11  and  11 A  are circuit diagrams of another accessory; 
         FIGS.  12  and  12 A  are cross-sectional views of another stylus in different stages of assembly; 
         FIG.  13    is a cross-sectional view of a hollow tip interface component; 
         FIG.  13 A  is a cross-sectional view of a tip portion of an accessory that includes the hollow tip interface component of  FIG.  13   ; 
         FIG.  13 B  is a view of the tip portion of  FIG.  13 A , taken from line XIIIB-XIIIB of  FIG.  13 A ; 
         FIG.  14    is a side view of a spherical tip interface component; 
         FIG.  14 A  is a cross-sectional view of a tip portion of an accessory that includes the spherical tip interface component of  FIG.  14   ; 
         FIG.  14 B  is a view of the tip portion of  FIG.  14 A , taken from line XIVB-XIVB of  FIG.  14 A ; 
         FIG.  15    is a side view of a spherical tip interface component; 
         FIG.  15 A  is a cross-sectional view of a tip portion of an accessory that includes the spherical tip interface component of  FIG.  15   ; 
         FIG.  15 B  is a cross-sectional view of a tip portion of an accessory that includes the spherical tip interface component of  FIG.  15    but with a compressible feature; 
         FIG.  15 C  is a view of the tip portion of  FIG.  15 A , taken from line XVC-XVC of  FIG.  15 B ; 
         FIG.  16    is a cross-sectional view of a portion of an accessory that includes certain grounding features; 
         FIG.  16 A  is a view of the accessory of  FIG.  16   , taken from line XVIA-XVIA of  FIG.  16   ; 
         FIG.  17    is a cross-sectional view of a portion of an accessory that includes other certain grounding features; 
         FIG.  17 A  is a view of the accessory of  FIG.  17   , taken from line XVIIA-XVIIA of  FIG.  17   ; 
         FIG.  18    is a cross-sectional view of a portion of an accessory that includes yet other certain grounding features; 
         FIG.  18 A  is a view of the accessory of  FIG.  18   , taken from line XVIIIA-XVIIIA of  FIG.  18   ; 
         FIG.  19    is a cross-sectional view of a portion of an accessory that includes yet other certain grounding features; and 
         FIG.  19 A  is a view of the accessory of  FIG.  19   , taken from line XIXA-XIXA of  FIG.  19   . 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the various embodiments described herein. Those of ordinary skill in the art will realize that these various embodiments are illustrative only and are not intended to be limiting in any way. Other embodiments will readily suggest themselves to such skilled persons having the benefit of this disclosure. 
     In addition, for clarity purposes, not all of the routine features of the embodiments described herein are shown or described. One of ordinary skill in the art will readily appreciate that in the development of any such actual embodiment, numerous embodiment-specific decisions may be required to achieve specific design objectives. These design objectives will vary from one embodiment to another and from one developer to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine engineering undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
     The present disclosure relates to one or more power efficient styli for interacting with a sensor assembly of an electronic device, such as for generating a graphical object on a display of the electronic device. 
     Systems, methods, and computer-readable media for enabling a power efficient stylus with electrostatic discharge protection for an electronic device are provided and described with reference to  FIGS.  1 - 19 A . 
       FIG.  1    is a schematic view of an illustrative system  1  with an electronic device  100  and a stylus  400 . Stylus  400  (e.g., a marking tool, smart pen, smart brush, wand, chisel, user-manipulated electronic input device, hand-held input device, and the like, or any other suitable accessory, such as a glove) may be configured to provide input to electronic device  100  (e.g., a tablet computer, laptop computer, desktop computer, and the like). A system user may manipulate the orientation and position of stylus  400  relative to an input surface of electronic device  100  to convey information to electronic device  100 , such as, but not limited to, writing, sketching, scrolling, gaming, selecting user interface elements, moving user interface elements, and so on. In many embodiments, the input surface of electronic device  100  may be a multi-touch display screen. However, in other embodiments, the input surface of electronic device  100  may be a non-display input surface, such as, but not limited to, a trackpad or drawing tablet. The input surface may be a foldable or flexible surface or display. System  1  may be used to capture free-form user input from stylus  400 . For example, the user can slide, move, draw, or drag a tip of stylus  400  across the input surface of electronic device  100 , which, in response, may render a graphical object (e.g., a line) using a display positioned below the input surface. In such an example, the rendered graphical object may follow or otherwise correspond to the path of stylus  400  across the input surface of electronic device  100 . The thickness and/or shape and/or intensity and/or any other suitable rendered characteristic of the rendered graphical object may vary based, at least in part, on one, some, or each of various characteristics, including, but not limited to, a force or speed with which the user moves stylus  400  across the input surface, an angle of stylus  400  relative to the input surface (e.g., the inclination of stylus  400  relative to a plane of the input surface, a writing angle of stylus  400  relative to a horizontal writing line traversing the input surface, etc.), a variable setting of a variable input component of stylus  400 , which one of multiple tips of stylus  400  is interacting with the input surface, a variable setting of an application running on electronic device  100  (e.g., a virtual drawing space application), and/or a combination thereof. Collectively, stylus  400  and electronic device  100  may be referred to herein as a “user input” system  1 . 
     Broadly and generally, system  1  may be operative to determine and/or estimate one or more outputs of stylus  400  (and/or changes therein over time as a scalar or vector quantity), to interpret the user&#39;s manipulation thereof as input to electronic device  100 . For example, system  1  may be operative to estimate: the magnitude of force applied by a user&#39;s grip to stylus  400  (e.g., non-binary estimate of magnitude as a scalar or vector quantity); a magnitude (e.g., non-binary estimate of magnitude as a scalar or vector quantity) of force applied (e.g., force applied F a ) by stylus  400  to the input surface of electronic device  100 ; the location at which or the area over which stylus  400  may touch or nearly touch the input surface of electronic device  100 ; a polar angle of stylus  400  relative to a plane of the input surface (e.g., inclination of stylus  400  (e.g., a polar angle  118  (θ) (e.g., as may be defined between a vector normal to the plane of input surface  110   a  and a longitudinal axis  120  of stylus  400 , such as a zenith))); an azimuthal angle of stylus  400  relative to an axis of the input surface (e.g., an azimuthal angle  122  (Φ) (e.g., as may be defined between the polar angle  118  (θ) and a reference vector within the plane of input surface  110   a , such as an axis)); a vector or scalar representation of the angular position of stylus  400  relative to a plane of the input surface; three-dimensional coordinates (e.g., spherical, Cartesian, and so on) of one or more points along the length of stylus  400  relative to the input surface; and so on. In many embodiments, system  1  may be operative to monitor such variables over time to estimate rates of change therein as either scalar or vector quantities (e.g., velocity, acceleration, and so on). The operation of estimating or determining two-dimensional position coordinates of stylus  400  as a point (or area) within or parallel to a plane of the input surface, whether such operation is performed by electronic device  100 , performed by stylus  400 , and/or performed, at least in part, as a result of cooperation therebetween (or with one or more other electronic devices), is generally referred to herein as “locating” the stylus. 
     Electronic device  100  and/or stylus  400  can be configured to estimate and/or monitor the location of stylus  400  over time and compute differential or integral quantities such as, but not limited to, acceleration, velocity, total force applied, path length, and so on. For example, the operation of estimating the velocity and/or acceleration of stylus  400  relative to the input surface as stylus  400  is moved across that surface, whether such operation is performed by electronic device  100 , performed by stylus  400 , and/or performed, at least in part, as a result of cooperation therebetween (or with one or more other electronic devices), is generally referred to herein as estimating the “planar motion” of the stylus. The operation of estimating the angular velocity and/or acceleration of stylus  400  relative to a plane of the input surface as it is moved thereacross, whether performed by electronic device  100 , performed by stylus  400 , and/or performed, at least in part, as a result of cooperation therebetween (or with one or more other electronic devices), is generally referred to herein as estimating the “angular motion” of the stylus. Additionally or alternatively, electronic device  100  and/or stylus  400  can be configured to estimate the distance (e.g., Z-height) of a portion of stylus  400  (e.g., the tip of the stylus) from the input surface of device  100 , and such an estimated distance may be used to determine a “make or break” event between the stylus and device, such as for making a determination when a drawn graphical line should start or stop or a stylus lift off event should occur. 
     Electronic device  100  may be any portable, mobile, or hand-held electronic device configured to interact with stylus  400  for changing any suitable characteristic(s) of device  100  (e.g., any suitable graphical object input tool characteristics that may be utilized to render a graphical object) in response to manipulation of stylus  400  across an input surface of electronic device  100 . Alternatively, electronic device  100  may not be portable at all, but may instead be generally stationary. Electronic device  100  can include, but is not limited to, a media player, video player, still image player, game player, other media player, music recorder, movie or video camera or recorder, still camera, other media recorder, radio, medical equipment, domestic appliance, transportation vehicle instrument, musical instrument, calculator, cellular telephone, other wireless communication device, personal digital assistant, remote control, pager, computer (e.g., a desktop, laptop, tablet, server, etc.), merchant accessory (e.g., signature pad (e.g., as may be used in a check-out line of a merchant store during payment processing)), monitor, television, stereo equipment, set up box, set-top box, wearable device (e.g., watch, clothing, etc.), boom box, modem, router, printer, and combinations thereof. Electronic device  100  may include any suitable control circuitry or processor  102 , memory  104 , communications component  106 , power supply  108 , input component  110 , and output component  112 . Electronic device  100  may also include a bus  114  that may provide one or more wired or wireless communication links or paths for transferring data and/or power to, from, or between various other components of device  100 . Device  100  may also be provided with a housing  101  that may at least partially enclose one or more of the components of device  100  for protection from debris and other degrading forces external to device  100 . In some embodiments, one or more of the components may be provided within its own housing (e.g., input component  110  may be an independent keyboard or mouse within its own housing that may wirelessly or through a wire communicate with processor  102 , which may be provided within its own housing). In some embodiments, one or more components of electronic device  100  may be combined or omitted. Moreover, electronic device  100  may include other components not combined or included in  FIG.  1   . For example, device  100  may include any other suitable components or several instances of the components shown in  FIG.  1   . For the sake of simplicity, only one of each of the components is shown in  FIG.  1   . 
     Memory  104  may include one or more storage mediums, including for example, a hard-drive, flash memory, permanent memory such as read-only memory (“ROM”), semi-permanent memory such as random access memory (“RAM”), any other suitable type of storage component, or any combination thereof. Memory  104  may include cache memory, which may be one or more different types of memory used for temporarily storing data for electronic device applications. Memory  104  may store media data (e.g., music and image files), software (e.g., applications for implementing functions on device  100  (e.g., virtual drawing space applications, stylus detection applications, etc.)), firmware, preference information (e.g., media playback preferences), lifestyle information (e.g., food preferences), exercise information (e.g., information obtained by exercise monitoring equipment), transaction information (e.g., information such as credit card information), wireless connection information (e.g., information that may enable device  100  to establish a wireless connection), subscription information (e.g., information that keeps track of podcasts or television shows or other media a user subscribes to), contact information (e.g., telephone numbers and e-mail addresses), calendar information, any other suitable data, or any combination thereof. 
     Communications component  106  may be provided to allow device  100  to communicate with one or more other electronic devices or servers or subsystems (e.g., stylus  400 ) using any suitable communications protocol(s). For example, communications component  106  may support Wi-Fi (e.g., an 802.11 protocol), Ethernet, Bluetooth™, near field communication (“NFC”), radio-frequency identification (“RFID”), high frequency systems (e.g., 900 MHz, 2.4 GHz, and 5.6 GHz communication systems), infrared, transmission control protocol/internet protocol (“TCP/IP”) (e.g., any of the protocols used in each of the TCP/IP layers), hypertext transfer protocol (“HTTP”), BitTorrent™, file transfer protocol (“FTP”), real-time transport protocol (“RTP”), real-time streaming protocol (“RTSP”), secure shell protocol (“SSH”), any other communications protocol, or any combination thereof. Communications component  106  may also include circuitry that can enable device  100  to be electrically coupled to another device or server or subsystem (e.g., stylus  400  or another user electronic device or server) and communicate with that other device, either wirelessly or via a wired connection. 
     Power supply  108  may provide power to one or more of the components of device  100 . In some embodiments, power supply  108  can be coupled to a power grid (e.g., when device  100  is not a portable device, such as a desktop computer). In some embodiments, power supply  108  can include one or more batteries for providing power (e.g., when device  100  is a portable device, such as a cellular telephone). As another example, power supply  108  can be configured to generate power from a natural source (e.g., solar power using solar cells). 
     One or more input components  110  may be provided to permit a user to interact or interface with device  100  and/or to sense certain information about the ambient environment. For example, input component  110  can take a variety of forms, including, but not limited to, a touch pad, trackpad, dial, click wheel, scroll wheel, touch screen, ultrasonic line sensor, ultrasonic imaging array, one or more buttons (e.g., a keyboard), mouse, joy stick, track ball, switch, photocell, force-sensing resistor (“FSR”), encoder (e.g., rotary encoder and/or shaft encoder that may convert an angular position or motion of a shaft or axle to an analog or digital code), microphone, camera, scanner (e.g., a barcode scanner or any other suitable scanner that may obtain product identifying information from a code, such as a linear barcode, a matrix barcode (e.g., a quick response (“QR”) code), or the like), proximity sensor (e.g., capacitive proximity sensor), biometric sensor (e.g., a fingerprint reader or other feature recognition sensor, which may operate in conjunction with a feature-processing application that may be accessible to electronic device  100  for authenticating or otherwise identifying or detecting a user), line-in connector for data and/or power, force sensor (e.g., any suitable capacitive sensors, pressure sensors, strain gauges, sensing plates (e.g., capacitive and/or strain sensing plates), etc.), temperature sensor (e.g., thermistor, thermocouple, thermometer, silicon bandgap temperature sensor, bimetal sensor, etc.) for detecting the temperature of a portion of electronic device  100  or an ambient environment thereof, a performance analyzer for detecting an application characteristic related to the current operation of one or more components of electronic device  100  (e.g., processor  102 ), motion sensor (e.g., single axis or multi axis accelerometers, angular rate or inertial sensors (e.g., optical gyroscopes, vibrating gyroscopes, gas rate gyroscopes, or ring gyroscopes), linear velocity sensors, and/or the like), magnetometer (e.g., scalar or vector magnetometer), pressure sensor, light sensor (e.g., ambient light sensor (“ALS”), infrared (“IR”) sensor, etc.), thermal sensor, acoustic sensor, sonic or sonar sensor, radar sensor, image sensor, video sensor, global positioning system (“GPS”) detector, radio frequency (“RF”) detector, RF or acoustic Doppler detector, RF triangulation detector, electrical charge sensor, peripheral device detector, event counter, and any combinations thereof. Each input component  110  can be configured to provide one or more dedicated control functions for making selections or issuing commands associated with operating device  100 . 
     Electronic device  100  may also include one or more output components  112  that may present information (e.g., graphical, audible, and/or tactile information) to a user of device  100 . An output component of electronic device  100  may take various forms, including, but not limited to, audio speakers, headphones, data and/or power line-outs, visual displays (e.g., for transmitting data via visible light and/or via invisible light), antennas, infrared ports, flashes (e.g., light sources for providing artificial light for illuminating an environment of the device), tactile/haptic outputs (e.g., rumblers, vibrators, etc.), taptic components (e.g., components that are operative to provide tactile sensations in the form of vibrations), and any combinations thereof. 
     For example, electronic device  100  may include a display as output component  112 . Display  112  may include any suitable type of display or interface for presenting visual data to a user. In some embodiments, display  112  may include a display embedded in device  100  or coupled to device  100  (e.g., a removable display). Display  112  may include, for example, a liquid crystal display (“LCD”), a light emitting diode (“LED”) display, an organic light-emitting diode (“OLED”) display, a surface-conduction electron-emitter display (“SED”), a carbon nanotube display, a nanocrystal display, an organic electroluminescence display, electronic ink, or another type of display technology or combination of display technology types. Alternatively, display  112  can include a movable display or a projecting system for providing a display of content on a surface remote from electronic device  100 , such as, for example, a video projector, a head-up display, or a three-dimensional (e.g., holographic) display. As another example, display  112  may include a digital or mechanical viewfinder, such as a viewfinder of the type found in compact digital cameras, reflex cameras, or any other suitable still or video camera. In some embodiments, display  112  may include display driver circuitry, circuitry for driving display drivers, or both. Display  112  can be operative to display content (e.g., media playback information, application screens for applications implemented on electronic device  100 , information regarding ongoing communications operations, information regarding incoming communications requests, device operation screens, etc.) that may be under the direction of processor  102 . Display  112  can be associated with any suitable characteristic dimensions defining the size and shape of the display. For example, the display can be rectangular or have any other polygonal shape, or alternatively can be defined by a curved or other non-polygonal shape (e.g., a circular display). Display  112  can have one or more primary orientations for which an interface can be displayed, or can instead or in addition be operative to display an interface along any orientation selected by a user. 
     It should be noted that one or more input components  110  and one or more output components  112  may sometimes be referred to collectively herein as an input/output (“I/O”) component or I/O interface  111  (e.g., input component  110  and display  112  as I/O component or I/O interface  111 ). For example, input component  110  and display  112  may sometimes be a single I/O component  111 , such as a touch screen, that may receive input information through a user&#39;s and/or stylus&#39; touch of a display screen and that may also provide visual information to a user via that same display screen. Input component  110  of electronic device  100  may provide an input surface relative to which a system user may manipulate the orientation and position of stylus  400  to convey information to electronic device  100 . In many embodiments, such an input surface of input component  110  of electronic device  100  may be provided as a portion of a multi-touch display screen assembly (e.g., as a portion of I/O interface  111  with a display output component  112 ). However, in other embodiments, such an input surface of input component  110  of electronic device  100  may be a non-display input surface, such as, but not limited to, a trackpad or drawing tablet, whether or not device  100  may also include a display output component. The input surface of input component  110  may be a foldable or flexible surface or display. 
     Processor  102  of device  100  may include any processing circuitry operative to control the operations and performance of one or more components of electronic device  100 . For example, processor  102  may be used to run one or more applications, such as an application  103 . Application  103  may include, but is not limited to, one or more operating system applications, firmware applications, virtual drawing space applications, stylus or other suitable accessory detection applications, media playback applications, media editing applications, pass applications, calendar applications, state determination applications (e.g., device state determination applications, stylus state determination applications, accessory state determination applications, etc.), biometric feature-processing applications, compass applications, health applications, thermometer applications, weather applications, thermal management applications, force sensing applications, device diagnostic applications, video game applications, or any other suitable applications. For example, processor  102  may load application  103  as a user interface program or any other suitable program to determine how instructions or data received via an input component  110  (e.g., due to interaction with a tip of stylus  400 ) and/or any other component of device  100  (e.g., stylus data from stylus  400  via communications component  106 , etc.) may manipulate the one or more ways in which information may be stored on device  100  (e.g., in memory  104 ) and/or provided to a user via an output component  112  and/or to a remote subsystem (e.g., to stylus  400  and/or to any other electronic device or server via communications component  106 ). Application  103  may be accessed by processor  102  from any suitable source, such as from memory  104  (e.g., via bus  114 ) or from another device or server (e.g., from stylus  400  via communications component  106 , and/or from any other suitable remote source via communications component  106 ). Electronic device  100  (e.g., processor  102 , memory  104 , or any other components available to device  100 ) may be configured to process graphical data at various resolutions, frequencies, intensities, and various other characteristics as may be appropriate for the capabilities and resources of device  100 . Processor  102  may include a single processor or multiple processors. For example, processor  102  may include at least one “general purpose” microprocessor, a combination of general and special purpose microprocessors, instruction set processors, graphics processors, video processors, and/or related chips sets, and/or special purpose microprocessors. Processor  102  also may include on board memory for caching purposes. Processor  102  may be implemented as any electronic device capable of processing, receiving, or transmitting data or instructions. For example, process  102  can be a microprocessor, a central processing unit, an application-specific integrated circuit, a field-programmable gate array, a digital signal processor, an analog circuit, a digital circuit, or combination of such devices. Processor  102  may be a single-thread or multi-thread processor. Processor  102  may be a single-core or multi-core processor. Accordingly, as described herein, the term “processor” may refer to a hardware-implemented data processing device or circuit physically structured to execute specific transformations of data including data operations represented as code and/or instructions included in a program that can be stored within and accessed from a memory. The term is meant to encompass a single processor or processing unit, multiple processors, multiple processing units, analog or digital circuits, or other suitably configured computing element or combination of elements. 
     Stylus  400  may be any suitable accessory, digital input tool, marking tool, smart pen, smart brush, wand, chisel, user-manipulated electronic input device, hand-held input device, and/or the like that may be configured to interact with (e.g., provide input to) electronic device  100 . Stylus  400  may include any suitable control circuitry or processor  402 , which may be similar to any suitable processor  102  of device  100 , application  403 , which may be similar to any suitable application  103  of device  100 , memory  404 , which may be similar to any suitable memory  104  of device  100 , communications component  406 , which may be similar to any suitable communications component  106  of device  100 , power supply  408 , which may be similar to any suitable power supply  108  of device  100 , input component  410 , which may be similar to any suitable input component  110  of device  100 , output component  412 , which may be similar to any suitable output component  112  of device  100 , I/O interface  411 , which may be similar to any suitable I/O interface  111  of device  100 , bus  414 , which may be similar to any suitable bus  114  of device  100 , and/or housing  401 , which may be similar to any suitable housing  101  of device  100 . In some embodiments, one or more components of stylus  400  may be combined or omitted. Moreover, stylus  400  may include other components not combined or included in  FIG.  1   . For example, stylus  400  may include any other suitable components or several instances of the components shown in  FIG.  1    or only some but not all of the components shown in  FIG.  1   . For the sake of simplicity, only one of each of the components is shown in  FIG.  1   . 
     Moreover, as shown, system  1  may include one or more additional styli, such as one or more of styli  400   a ,  400   b , and  400   c , and/or one or more other types of accessory, such as accessory  400   d , each of which may include any suitable components, such as a processor, application, memory, communications component, power supply, input component, output component, I/O interface, bus, housing, and/or the like, and may be similar to stylus  400 . While each stylus of system  1  may be operative to be used with respect to an input surface of device  100  (e.g., one at a time (e.g., by a user)), each stylus of system  1  may differ from one another with respect to one or more physical characteristics (e.g., color, weight, size, shape, material, circuitry, etc.) and/or with respect to one or more device input tool characteristics (e.g., graphical object input tool characteristics) associated with the stylus as may be determined by device  100  for defining any suitable device characteristic(s) (e.g., rendered characteristic(s) (e.g., color, thickness, shape, intensity, and/or the like) of a graphical object rendered by device  100 ) in response to manipulation of the stylus with respect to an input surface of device  100 . 
     Generally and broadly,  FIGS.  1 A- 1 D  reference user input system  1  including electronic device  100  and stylus  400 . A user U manipulates the orientation and position of stylus  400  relative to input surface input component  110   a  (e.g., a particular input component  110 ) of electronic device  100  in order to convey information to electronic device  100 . User input system  1  may be configured to perform or coordinate multiple operations such as, but not limited to, locating stylus  400 , estimating the angular position of stylus  400 , estimating the magnitude of force by stylus  400  to input surface  110   a , determining a variable setting of a variable input component  410  of stylus  400 , determining a variable setting of an application  103  running on electronic device  100  (e.g., a virtual drawing space application), and/or a combination thereof. User input system  1  can perform these and other operations at the same time or at different times. In one non-limiting example, the operation of determining the location of stylus  400  can be performed simultaneously with the operation of determining the angular position of stylus  400 , while the operation of estimating the magnitude of force by stylus  400  to input surface  110   a  may be performed only periodically and/or based on whether electronic device  100  is configured to accept force input from stylus  400  given a particular operational mode of electronic device  100  (or of stylus  400 ) at a particular time. 
       FIG.  1 A  depicts user U gripping a barrel or handle or body portion  417  of stylus  400  extending between a front tip portion  415  of stylus  400  and a rear tip portion  419  of stylus  400 . User U may slide a tip portion, such as tip portion  415 , of stylus  400  across input surface  110   a  of electronic device  100  to interact with a user interface presented or rendered on display output component  112   a  of electronic device  100 , which may be positioned below at least a portion of input surface  110   a  or integrated with at least a portion of input surface  110   a  to provide I/O interface  111   a  of device  100 . Although, in other embodiments, it is to be understood that device  100  may not include a display output component or may not include a display output component co-located with input surface  110   a . Input surface  110   a  may be a foldable or flexible surface or display. As shown in  FIGS.  1 A- 1 D , device  100  may be presented as a tablet computing device as an example only, while many other electronic devices (with or without displays positioned below a stylus input surface) are envisioned. For example, the electronic device of user input system  1  can be implemented as a peripheral input device, a trackpad, a drawing tablet, and the like. 
     Stylus  400  may take various forms to facilitate use and manipulation by user U. In the illustrated example of  FIGS.  1 A- 1 D , stylus  400  may have a general form of a writing instrument, such as a pen or a pencil with a cylindrical body  417  with two ends, such as a first end terminated at front portion  415  and a second end terminated at rear portion  419 . Either one or both of portions  415  and  419  can be removable and/or replaceable (e.g., by a user), affixed to body  417 , or an integral part of body  417 . User U may slide front portion  415  of stylus  400  across input surface  110   a  to convey information to electronic device  100 . Electronic device  100  can interpret the user&#39;s manipulation of stylus  400  in any implementation-specific and suitable manner. 
     Body  417  of stylus  400  can be formed from any number of suitable materials, such as from plastics, metals, ceramics, laminates, glass, sapphire, wood, leather, synthetic materials, dielectric material, or any other material or combination of materials. Body  417  can form an outer surface (or partial outer surface) and protective case for one or more internal components of stylus  400  (e.g., as a portion of housing  401 ). Body  417  can be formed of one or more components operably connected together, such as a front piece and a back piece or a top clamshell and a bottom clamshell. Alternatively, body  417  can be formed of a single piece (e.g., uniform body or unibody). In some embodiments, body  417  may be configured, partially or entirely, as an optical signal diffuser to diffuse an infrared signal or another optical signal such as the light emitted from a multi-color light-emitting diode. In other cases, body  417  may be configured, entirely or partially, as an antenna window, allowing for wireless communications and/or electric fields to pass therethrough. Body  417  can be formed from a material doped with an agent configured to provide body  417  with a selected color, hardness, elasticity, stiffness, reflectivity, refractive pattern, texture, and so on. In other examples, the doping agent can confer other properties to body  417  including, but not necessarily limited to, electrical conductivity and/or insulating properties, magnetic and/or diamagnetic properties, chemical resistance and/or reactivity properties, infrared and/or ultraviolet light absorption and/or reflectivity properties, visible light absorption and/or reflectivity properties, antimicrobial and/or antiviral properties, oleophobic and/or hydrophobic properties, thermal absorption properties, pest repellant properties, colorfast and/or anti-fade properties, antistatic properties, liquid exposure reactivity properties, and so on. 
     Body  417  can exhibit a constant or a variable diameter cross-section. As illustrated, for example, the cylindrical cross-section view of body  417  may maintain a substantially constant diameter from tip portion  415  to rear portion  419 . In other embodiments, body  417  can include a variable cross-section (e.g., a “profile” of body  417  can change across the length of body  417 ). In one example, the diameter of body  417  may be smaller near tip portion  415  than at rear portion  419 . In some examples, the diameter of body  417  may bulge outward in the middle of body  417  between portions  415  and  419 . In some cases, the profile of body  417  can follow a mathematical function such as a bump function, a Gaussian function, or a step function. Body  417  may include one or more grip features (not shown) such as embossments or impressions, closely-spaced channels, protrusions, projections, and/or the like. In some cases, a grip feature can be formed from a different material than body  417  (e.g., grip feature(s) may be formed from a polymer material exhibiting high friction). 
     Although illustrated as a cylinder, body  417  need not take a cylindrical shape in all embodiments. Accordingly, as used herein, the term “diameter” may refer to the linear distance that can connect two points of a two-dimensional shape, whether the shape is circular or otherwise. For example, stylus  400  can include a body  417  with an n-sided polygonal cross-section (e.g., a vesica piscis cross-section, a triangular cross-section, a square cross-section, a pentagonal cross-section, and so on) that either varies in diameter or is constant in diameter. In some examples, a cross-section of body  417  may be axially symmetric, although this is not required, as certain styluses in accordance with embodiments described herein may include body  417  with a cross-section that is reflectionally symmetric along one axis while being reflectionally asymmetric along another. In still further examples, body  417  can be formed into an ergonomic shape, including grooves, indents, and/or protrusions configured to enhance the comfort of user U. In some cases, body  417  may include a tapered section that decreases in diameter, linearly or non-linearly, toward tip portion  415 . The diameter of body  417  at the interface of body  417  and tip portion  415  may be substantially similar to the diameter of tip portion  415  at that location. In this manner, the external surfaces of portions  415  and  417  may form a substantially continuous external surface of housing  401  of stylus  400 . Additionally or alternatively, the diameter of body  417  at the interface of body  417  and rear portion  419  may be substantially similar to the diameter of rear portion  419  at that location. In this manner, the external surfaces of portions  417  and  419  may form a substantially continuous external surface of housing  401  of stylus  400 . 
     One or more of portions  415 ,  417 , and  419  of stylus  400  can define one or more apertures  416  in which one or more input components  410  and/or one or more output components  412  of stylus  400 , such as a button, a dial, a slide, a force pad, a touch pad, audio component, haptic component, and the like, may at least partially reside and/or through which such component(s) may be at least partially exposed. The apertures (and, correspondingly, the input/output components associated therewith) can be defined at a lower end of body  417  nearby tip portion  415 , such that the input/output components may be conveniently located near where user U may rest the user&#39;s forefinger when grasping stylus  400 . As one example, an aperture  416  may expose at least a portion of a simple mechanical switch or button input component  410  that may be manipulated by user U for adjusting a variable setting of stylus  400  (e.g., stylus  400  may be configured to operate in a first mode when such an input component is manipulated in a first manner and in a second mode when such an input component is manipulated in a second manner (e.g., to select different patterns of stylus  400   b  described herein)). 
     Rear portion  419  of stylus  400 , or more generally a “cap” of stylus  400 , may be configured to provide a cosmetic end to body  417 . In some cases, rear portion  419  may be formed integrally with body  417 . In some cases, rear portion  419  may be formed similarly to front portion  415  for providing another tip feature for interacting with an input surface of device  100  (e.g., stylus  400  may be flipped over by user U to drag portion  419  across input surface input component  110   a  of electronic device  100  rather than to drag portion  415  across input surface input component  110   a  of electronic device  100 , which may enable different user-selectable interactions with device  100 ). Any portion or the entirety of rear portion  419  may expose or provide at least a portion of a simple mechanical switch or button or any other suitable input component  410  that may be manipulated by user U for adjusting a variable setting of stylus  400  (e.g., stylus  400  may be configured to operate in a first mode when such an input component is manipulated in a first manner and in a second mode when such an input component is manipulated in a second manner (e.g., to select different patterns of stylus  400   b  described herein)). 
     Tip portion  415  of stylus  400 , or more generally a “tip” of stylus  400 , may be configured to contact or nearly contact input surface  110   a  of device  100  in order to facilitate interaction between user U and device  100 . Tip  415  may taper to a point, similar to a pen, so that user U may control stylus  400  with precision in a familiar form factor. In some examples, tip  415  may be blunt or rounded, as opposed to pointed, or may take the form of a rotatable or fixed ball. Tip  415  may be formed from a softer material than input surface  110   a . For example, tip  415  can be formed from a silicone, a rubber, a fluoro-elastomer, a plastic, a nylon, conductive or dielectric foam, a brass or metal ball with a polymer coating or dielectric coating (e.g., a thin coating with a high dielectric constant) or any other suitable coating, or any other suitable material or combination of materials. In this manner, drawing of tip  415  across input surface  110   a  may not cause damage to input surface  110   a  or layers applied to input surface  110   a , such as, but not limited to, anti-reflective coatings, oleophobic coatings, hydrophobic coatings, cosmetic coatings, ink layers, and the like. Tip  415  can be configured to be removably attached to body  417 , such as via threadings/screws, detents and/or recesses, interference-fit or snap-fit, and/or magnetic attraction, and/or the like, and electrically coupled capacitively, such as through a pogo-pin, spring, and/or the like. 
     Electronic device  100  may locate and/or estimate the angular position of stylus  400  substantially in real time. Device  100  can perform these operations with and/or without communications from stylus  400 . As shown in  FIGS.  1 A- 1 D , device  100  may be depicted as a tablet computing device, although this form-factor is not required of all embodiments (as noted above). For example, device  100  can be any suitable device, such as a desktop computer, laptop computer, cellular phone, an industrial or commercial computing terminal, a medical device, a peripheral or integrated input device, a hand-held or battery powered portable electronic device, a navigation device, a wearable device, and so on. Display output component  112   a  may be positioned below input surface  110   a  or may be integrated with input surface  110   a.    
     The communication interfaces, whether between electronic device  100  and stylus  400  or between device  100  and another device or server, or otherwise, can be implemented as capacitive coupling interfaces (e.g., via I/O interfaces  111  and  411  (e.g., as capacitive coupling interface data  51  (e.g., signal(s) received by or adjusted by or made available by one of the interfaces to the other interface))), inductive interfaces, resonant interfaces, optical interfaces, acoustic interfaces, magnetic interfaces, wireless interfaces, Bluetooth interfaces (e.g., via communication components  106  and  406  (e.g., as wired/wireless communication interface data  56 )), universal serial bus interfaces, Wi-Fi interfaces, TCP/IP interfaces, network communications interfaces, or any other suitable communication interfaces. In some embodiments, stylus  400  may not be configured to communicate with device  100  via any communication component interfaces (e.g., stylus  400  may not be provided with any communications component (e.g., no communications component  406 ) but may still communicate with device  100  using any suitable I/O interface  411  (e.g., via I/O interfaces  111  and  411  (e.g., as capacitive coupling interface data  51 )))). Electronic device  100  may provide information related to externally connected or communicating devices and/or software executing on such devices, messages, video, operating commands, and so forth (and may receive any of the foregoing from an external device), in addition to communications. Input surface  110   a  may cooperate with housing  101  of device  100  to form an external surface thereof. In some cases, a front surface of input surface  110   a  can be flush with an external surface of housing  101 , although this is not required of all embodiments. In some examples, input surface  110   a  may stand proud of at least a portion of housing  101 . Input surface  110   a  may be formed from glass or another suitable material, such as plastic, sapphire, metal, ceramic, ion-implanted glass, and so on. In some cases, input surface  110   a  may be a solid material, whereas in other cases, input surface  110   a  may be formed by laminating or adhering several materials together. Display component  112   a  may be positioned below, or integrated with, input surface  110   a , where device  100  may utilize display  112   a  to render images to convey information to the user. Display  112   a  can be configured to show text, colors, line drawings, photographs, animations, video, and the like. Input surface  110   a  and/or display  112   a  may provide a foldable or flexible surface or display. 
     Device  100  can also include a sensor layer input component  110   b  positioned below, or integrated with, input surface  110   a  and/or display  112   a , where device  100  may utilize the sensor layer to, among other purposes, detect the presence and/or location of stylus  400  on input surface  110   a . In other examples, device  100  may utilize sensor layer  110   b  to detect the presence of another object on input surface  110   a , such as a finger of the user. In still further examples, device  100  may utilize sensor layer  110   b  to detect the force with which an object, such as stylus  400 , presses on input surface  110   a . Such a sensor layer  110   b  (e.g., of input surface input component  110   a ) can be optically transparent or opaque. If sensor layer  110   b  of a particular embodiment is disposed within display  112   a , sensor layer  110   b  may be optically transparent so as to not impact the clarity of the display. In another example, sensor layer  110   b  may be disposed around the perimeter of the display, positioned below a bezel surrounding the display, and/or the like. In this embodiment, sensor layer  110   b  need not be optically transparent. Input surface  110   a  and/or sensor layer  110   b  may provide at least a portion of a foldable or flexible surface or display. Sensor layer  110   b  may be a metallic grid that may be positioned between and not blocking one or more light-emissive elements of I/O interface  111   a  (e.g., for providing on-cell or in-cell electrodes). Additionally or alternatively, electrodes of sensor layer  110   b  could be shared with display electronics of I/O interface  111   a  (e.g., for providing in-cell electrodes). 
     Next, reference is made to the operation of locating stylus  400  on input surface  110   a  of device  100  using sensor layer  110   b  of device  100 . Device  100  can locate an interface portion, such as tip  415 , of stylus  400 , and estimate the Cartesian coordinates thereof, in a number of suitable ways. In typical embodiments, stylus  400  is located as a result of cooperation between stylus  400  and device  100 . Generally and broadly, stylus  400  may be operative to generate and/or adjust (e.g., using any suitable I/O interface or I/O component or I/O circuitry  411 ) an electric field (e.g., an electric field having a small effective diameter along input surface  110   a , or an electric field where potential lines may be nearly spheres but where the electric field lines may be strongly curved but not circular). This “stylus electric field” (e.g., as adjusted and/or generated (e.g., caused) by stylus  400 ) may be provided by a stylus interface portion (e.g., tip  415 ) and may intersect input surface  110   a  when the stylus interface portion of stylus  400  is placed on or near surface  110   a . Device  100  may detect the stylus electric field and estimate the location of stylus  400  (e.g., of the stylus interface portion (e.g., tip  415 ) based on the location (and/or area) at which the stylus electric field is detected). Sensor layer  110   b  may be configured to detect stylus electric fields caused by stylus  400 , where layer  110   b  may include a number of capacitance sensing nodes that can be located on or between any suitable layer on or within display  112   a  and/or on or within input surface  110   a . The capacitive sensing nodes may be formed, at least in part, from an optically transparent conductor, such as, but not limited to, metal oxides such as indium-tin oxide and antimony-tin oxide, nanowire patterns formed from silver nanowire, carbon nanotubes, platinum nanowire, gold nanowire, and so on, thin deposits of metal, and the like. The capacitive sensing nodes may be configured to operate in any suitable capacitance mode or projected capacitance touch (“PCT”) mode, such as a self-capacitance mode, a mutual capacitance mode, or any other suitable capacitance mode or combination thereof, thereby capacitively coupling to stylus  400  and detecting signals and fields caused by stylus  400 . 
     Stylus  400  may cause a substantially-spherical or hemispherical or any other suitably shaped stylus electric field to be provided thereby (e.g., from tip  415  by I/O circuitry  411 ). This stylus field may affect the capacitance (e.g., mutual capacitance or self-capacitance) of each capacitive sensing node nearby the stylus interface portion. Device  100  may locate stylus  400  on input surface  110   a  by monitoring each capacitive sensing node or an appropriate set of capacitive sensing nodes for these capacitive changes and estimating the location at which such changes (if any) have occurred. As used herein, the term “tip signal” may generally refer to an electrical signal provided by or received by stylus  400  at the stylus interface portion (e.g., tip  415 ). As used herein, the term “tip field” may generally refer to the stylus electric field provided by the stylus interface portion (e.g., tip  415 ) in response to the tip signal. The tip field may take any suitable shape, but in many embodiments, the tip field takes a substantially spherical (or hemispherical) shape and may be modeled as a point source monopole electric field. The area of input surface  110   a  (or a plane parallel to input surface  110   a ) intersected by the tip field may be generally referred to herein as the “tip field intersection area,” which may be any suitable shape, such as substantially circular. A perimeter of the tip field intersection area may be defined as the boundary after which the power density (e.g., magnitude) of the tip field received by electronic device  100  may be below a selected threshold. In one example, the circumference of the tip field intersection area may be defined at the half-power point of the tip field. In other words, in this example, the tip field intersection area may be defined as a portion of input surface  110   a  intersected by the tip field with a magnitude at least greater than half of the power at which that field was provided. A charge footprint (e.g., charge profile) may be counted out as far as it is above a noise floor. 
     The tip signal can have at least one alternating current component that, via capacitive coupling or another suitable sensing technique, may be received (e.g., as the tip field) by the sensor layer of the electronic device. Many embodiments are described herein with reference to a sensor layer  110   b  of electronic device  100  that may be configured to detect the tip signal by monitoring mutual capacitance. However, it may be appreciated that electronic device  100  can be appropriately configured in any implementation-specific manner to detect the tip field. For example, electronic devices can include a sensor layer configured to monitor for changes in the self-capacitance of one or more capacitive sensor nodes. In other examples, an electronic device can be configured to operate in both a self-capacitance mode and a mutual capacitance mode. In other embodiments, other sensing techniques can be used to determine the location and relative position of the tip field. As noted above, sensor layer  110   b  can also be used to detect one or more fingers or the palm or the like of user U while simultaneously detecting the tip field. In these cases, electronic device  100  can accept both touch input and stylus input. 
     In many cases, processor  102  of device  100  may be configured to detect the tip signal received through sensor layer  110   b  from stylus  400  via capacitive coupling. Processor  102  may be configured to demodulate, decode, or otherwise filter one or more raw signals received from sensor layer  110   b  and/or from any other sensor/input component in order to obtain the tip signal, and/or data that may be modulated therewith and/or any other suitable data. The operation of obtaining the tip signal, as performed by processor  102  (or another component communicably coupled to sensor layer  110   b ), can be accomplished in a number of implementation-specific ways, suitable for any number of embodiments. Processor  102  may perform (or assist with the performance of) the operation of locating stylus  400  on input surface  110   a  employing any suitable techniques once the tip signal is obtained, and the tip field intersection area is determined. Processor  102  can further use such information for further processing and interpretation once the location of stylus  400  is estimated. 
     In many embodiments, processor  102  may be configured to obtain estimations of the location of stylus  400  within certain statistical bounds (e.g., within an error of 100 micrometers, within 50 micrometers, within 10 micrometers, or any other suitable bounds). One may appreciate that the accuracy and/or precision of the operation of locating stylus  400  by device  100  may differ from embodiment to embodiment. In some cases, the accuracy and/or precision of the operation(s) may be substantially fixed, whereas in other cases, the accuracy and/or precision of the operation(s) may be variable depending upon, among other variables, a user setting, a user preference, a speed of the stylus, an acceleration of the stylus, a setting of a program  103  operating on electronic device  100 , a setting of electronic device  100 , an operational mode of electronic device  100 , a power state of device  100 , a power state of stylus  400 , an identification of a setting or characteristic of stylus  400 , and so on. 
     The tip signal can include certain information and/or data that may be configured to identify stylus  400  to electronic device  100 . Such information may generally be referred to herein as “stylus identity” information (e.g., information indicative of a particular stylus tip of stylus  400   a  with a particular harmonic and/or phase as described herein). This information and/or data may be received by sensor layer  110   b  and interpreted, decoded, and/or demodulated by processor  100  of device  100 . Processor  102  may utilize stylus identity information (or an absence thereof) in any suitable manner including, but not limited to, accepting or rejecting input from a particular stylus, accepting input from multiple styli and/or from a single stylus, permitting or denying access to a particular functionality of the electronic device, applying a particular stylus profile, restoring one or more settings of the electronic device, notifying a third party that the stylus is in use, applying a setting to the electronic device, applying a setting to a program operating on the electronic device (e.g., which may include updating a user interface on display  112   a  or otherwise of device  100 ), changing a line thickness, color, pattern, erasure, and so on of a graphical object to be rendered by a graphics program of the electronic device, changing a setting of a video game operating on the electronic device, and so on. Processor  102  may be operative to receive stylus identity information for stylus  400 . Additionally or alternatively, processor  102  may be operative to receive stylus identity information from each one of two different styluses that may be interacting with device  100 . For example, processor  102  may be operative to determine that a first detected stylus is positioned 3 centimeters away from a second detected stylus, which may be communicated via display  112   a  to the user(s) in any suitable manner. Additionally or alternatively, any suitable data communicated from stylus  400  may be operative to include certain information and/or data that may serve to identify a particular setting or preference of the user or of the stylus (e.g., a current setting of a variable input component or other suitable reconfigurable characteristic of the stylus (e.g., data indicative of a particular property of an input component  410  of stylus  400 )), where such information may generally be referred to herein as “stylus setting” information (e.g., information indicative of a particular pattern of stylus  400   b  as described herein). Processor  102  may be operative to use stylus setting information (or an absence thereof) in any suitable manner including, but not limited to, applying a setting to the electronic device, applying a setting to a program operating on the electronic device (e.g., which may include updating a user interface on display  112   a  or otherwise of device  100 ), changing a line thickness, color, pattern, erasure, and so on of a graphical object to be rendered by a graphics program of the electronic device, changing a setting of a video game operating on the electronic device, and so on. 
     A stylus of system  1  may not be provided with any power supply (e.g., no battery or any other suitable power supply like power supply  408 ), such that the stylus may not be operative to generate any stylus electric field independently (e.g., without being stimulated by an external stimulus). Instead, a stylus may be provided with limited stylus I/O circuitry that may be operative to be stimulated by an external stimulus, such as a device stimulus that may be generated by device I/O circuitry of device I/O interface  111   a  of electronic device  100  and that may be operative to stimulate the stylus I/O circuitry when located proximate to device I/O interface  111   a  and/or by user U when holding stylus  400 , whereby that stimulation of the stylus I/O circuitry may be operative to enable the stylus I/O circuitry to provide any suitable stylus electric field that may then be detected by device  100  for estimating the location of the stylus. Not only may such stylus I/O circuitry be configured to require no internal power supply for providing a unique stylus electric field, but also such stylus I/O circuitry, when stimulated, may be configured to provide a stylus electric field that may be distinguishable by device  100  from an electric field that may be provided by a user&#39;s direct contact with device I/O interface  111   a.    
     For example,  FIGS.  2 - 2 G  illustrate stylus  400   a , alone and/or in combination with device  100  of system  1 , that may include stylus I/O circuitry  411   a , where stylus I/O circuitry  411   a  may be operative to be stimulated only by external stimulus, such as a device stimulus that may be generated by device I/O circuitry of device I/O interface  111   a  of electronic device  100  and/or by user U when holding stylus  400   a , whereby that stimulation of stylus I/O circuitry  411   a  may be operative to enable stylus I/O circuitry  411   a  to provide any suitable stylus electric field that may then be detected by device  100  for estimating the location of stylus  400 . As shown by  FIGS.  2  and  2 C , for example, stylus  400   a  may include a barrel or handle or body portion  417   a  extending between a front tip portion  415   a  and a rear tip portion  419   a , where body portion  417   a  may be configured to be held by user U as the user may slide a tip portion of stylus  400  across input surface  110   a  of device I/O interface  111   a  of device  100 . 
     Stylus I/O circuitry  411   a  may include body stylus circuitry  427   a  that may be electrically coupled to front tip stylus circuitry  426   a  and/or to rear tip stylus circuitry  436   a . Body stylus circuitry  427   a  may be any suitable circuitry that may be operative to be electrically coupled (e.g., capacitively coupled) to user U when user U is holding stylus  400   a  about at least a portion of body portion  417   a . As shown in  FIGS.  2  and  2 C , for example, body stylus circuitry  427   a  may be at least one conductive wire extending along at least a portion of a length of body portion  417   a  of stylus  400   a , which may be insulated by any suitable insulation  428   a . Alternatively, body stylus circuitry  427   a  may be provided by a conductive (e.g., copper) tape along a portion of body  417   a , where such tape may be positioned under any suitable insulation, such as a finger pad of any suitable material. Any suitable housing  401   a  may be provided to protect body stylus circuitry  427   a , such as a plastic housing. In some embodiments, such a housing may be operative to provide insulation  428   a . Additionally or alternatively, at least a portion of body stylus circuitry  427   a  may be at least partially exposed via housing  401   a  and/or insulation  428   a  for enabling direct contact by user U. When user U is holding stylus  400   a  about and/or along a portion of body  417   a , a capacitance or user-handle capacitor UHC may be inherently formed (e.g., as shown in  FIGS.  2 B,  2 E, and  2 G ). The capacitance of user-handle capacitor UHC may be relatively large compared to a panel to tip capacitance (e.g., electric field response capacitances SDC between front tip interface component  421   a  and each one of array trace row  111   ar  and array trace column  111   ac  of one or more nodes  111   an  proximate front tip interface component  421   a ), but not so large that electrostatic discharges would be likely to damage the device. For example, the capacitance of user-handle capacitor UHC may be any suitable capacitance, such as a capacitance in the range of 1.0 picofarad to 10.0 picofarads, as a panel to tip capacitance may be in the range of 50.0 femtofarads to 200.0 femtofarads. The capacitance of user-handle capacitor UHC may be able to stand off the voltage of typical electrostatic discharge impulses (e.g., 10 kilovolts or so). 
     Stylus I/O circuitry  411   a  may include a front tip interface component  421   a  that may provide at least a portion of front tip portion  415   a . Front tip interface component  421   a  may be the portion of stylus  400   a  configured to directly interface with device I/O interface  111   a . For example, front tip interface component  421   a  may be formed from any suitable material, including, but not limited to, silicone, rubber, fluoro-elastomer, plastic, nylon, conductive or dielectric foam, metal (e.g., brass (e.g., a brass ball with a dielectric or polymer coating (e.g., a thin coating with a high dielectric constant))), or any other suitable material or combination of materials. In this manner, drawing of front tip interface component  421   a  across input surface  110   a  may not cause damage to input surface  110   a  or layers applied to input surface  110   a , such as, but not limited to, anti-reflective coatings, oleophobic coatings, hydrophobic coatings, cosmetic coatings, ink layers, and the like. Front tip interface component  421   a  can be configured to be removably attached to body  417   a , such as via threadings/screws, detents and/or recesses, interference-fit or snap-fit, and/or magnetic attraction, and/or the like, and electrically coupled capacitively, such as through a pogo-pin, spring, and/or the like. Transit of any stylus electric field may be provided from front tip interface component  421   a  and not from other portions of stylus I/O circuitry  411   a . Front tip interface component  421   a  may be any suitable shape, such as a sphere or hemisphere or spherical cap, of any suitable size. For example, in some particular embodiments, front tip interface component  421   a  may be provided as a ball (e.g., a solder ball and/or brass ball) of any suitable diameter, such as 2 millimeters or 3.6 millimeters in diameter, or in the range of 1.7 millimeters to 2.3 millimeters, or in the range of 3.3 millimeters to 3.9 millimeters, or, as one example, a brass or metal ball with a diameter of 3.6 millimeters and with a coating thereabout of about 0.2 millimeters thickness. Front tip interface component  421   a  may be a metal or brass ball with a coating or a conductive polymer ball shape, with a total diameter of about 3.4 millimeters or 3.0 millimeters or 2.4 millimeters or 2.0 millimeters. Front tip interface component  421   a  may be configured to provide the same footprint area (e.g., tip field intersection area (e.g., of charge)) on input surface  110   a  no matter (e.g., substantially no matter) the angle of axis  120  with respect to a plane of input surface  110   a . The size of front tip interface component  421   a  may be made as small as possible to enable precise localization of front tip portion  415   a  with respect to device I/O interface  111   a.    
     Front tip stylus circuitry  426   a  may be positioned between and electrically coupled to each one of front tip interface component  421   a  and a portion (e.g., a front end) of body stylus circuitry  427   a . Front tip stylus circuitry  426   a  may be configured as any suitable circuitry that may be operative to provide a non-linear load between body stylus circuitry  427   a  and front tip interface component  421   a  when user U is holding body  417   a  of stylus  400   a  such that front tip interface component  421   a  of stylus  400   a  may be stimulated by a device stimulus that may be generated by device I/O circuitry of device I/O interface  111   a  of electronic device  100 . For example, front tip stylus circuitry  426   a  may include any suitable non-linear electrical circuitry  423   a  that may be electrically coupled (e.g., in series) between front tip interface component  421   a  and body stylus circuitry  427   a . Non-linear electrical circuitry  423   a  may include any suitable number of any suitable type(s) of non-linear electrical elements, such as at least one diode  422   a . Diode  422   a  may be any suitable type of diode, such as a Schottky diode, a transistor in diode configuration (e.g., a diode connected transistor), and/or the like. In some embodiments, non-linear electrical circuitry  423   a  may include any suitable number (e.g., two or three or four or more) of diodes  422   a  that may be coupled together in series (e.g., a cathode of one diode may be coupled to an anode of a next diode and/or the like) or in parallel. Alternatively, as shown, only a single diode  422   a  may be provided by non-linear electrical circuitry  423   a , where an anode A of diode  422   a  may be electrically coupled to body stylus circuitry  427   a  and where a cathode C of diode  422   a  may be electrically coupled to front tip interface component  421   a.    
     Device I/O circuitry of I/O interface  111   a  may be configured in any suitable manner to provide a device stimulus for stimulating front tip interface component  421   a  of stylus  400   a  when front tip interface component  421   a  of stylus  400  is positioned on or close to input surface input component  110   a  of I/O interface  111   a  as user U may drag front tip interface component  421   a  across input surface input component  110   a . For example, sensor layer  110   b  of the device I/O circuitry of I/O interface  111   a  may be configured to monitor changes in mutual capacitance that may be caused by a stylus electric field provided by stylus  400   a  at one or more capacitive sensing nodes of sensor layer  110   b . As shown in  FIGS.  2 A,  2 B,  2 D, and  2 E , for example, sensor layer  110   b  may be configured to provide an array of mutual capacitive sensors or sensing nodes that may be operative to enable mutual capacitance PCT sensing techniques. Sensor layer  110   b  may provide an array or grid of any suitable number of array trace columns  111   ac  and any suitable number of array trace rows  111   ar , any two of which may intersect to provide a sensing node  111   an . A capacitance or mutual node capacitor MNC may be inherently formed at each sensing node  111   an  (e.g., as shown in  FIGS.  2 A,  2 B,  2 D, and  2 E ). When any suitable electrical signal (e.g., transmit signal) TS may be provided along one, some, or each of array trace columns  111   ac  by any suitable transmitter circuitry T (e.g., a high frequency driven amplifier and/or a voltage source V controlled by a waveform w (e.g., a sinusoid or trapezoid shaped waveform) of any suitable magnitude (e.g., 6.5 volts amplitude (e.g., peak to peak)) and/or of any suitable frequency (e.g., 150 kHz or 70 kHz or 40 kHz or the like), or any other suitable configuration), any suitable electrical signal (e.g., receive signal) RS may be detected by any suitable receiver circuitry R that may be provided along each one of array trace rows  111   ar . While signal TS (e.g., a voltage) is applied to an array trace column  111   ac , bringing a finger or conductive stylus close to the surface of sensor layer  110   b  may change the local electrostatic field (e.g., in response to signal TS and/or capacitance MNC stimulating front tip interface component  421   a  of stylus  400   a ), which in turn may reduce the mutual capacitance. The capacitance change at every individual point on the array grid can be measured to determine the touch location accurately by measuring and analyzing the signal in the other axis, such as signal RS along each array trace row  111   ar . Mutual capacitance may allow multi-touch operation where multiple fingers, palms, or styli can be accurately tracked at the same time. For example, as shown in  FIGS.  2 A and  2 B , capacitance MNC and/or signal TS at one or more nodes  111   an  may be received by front tip interface component  421   a  and may stimulate front tip stylus circuitry  426   a , which, in turn, may be operative to provide a non-linear load between body stylus circuitry  427   a  and front tip interface component  421   a  for generating a stylus electric field response for changing the electric field local to one or more nodes  111   an . For example, the reaction of the stimulus and the non-linear load may create harmonics, which may then be received by one or more nodes, such as by node  111   an  of  FIGS.  2 A and  2 B  and/or by an associated array trace row  111   ar  and/or by an associated array trace column  111   ac , for example, via electric field response capacitances SDC between front tip interface component  421   a  and each one of array trace row  111   ar  and array trace column  111   ac  of one or more nodes  111   an  proximate front tip interface component  421   a . Such harmonics may then be detected as signal RS along an array trace row  111   ar  of one or more nodes  111   an  on the array grid and then such signals may be analyzed (e.g., using any suitable algorithms or detection applications  103  of device  100  (e.g., at processor  102  or any suitable circuitry (e.g., of I/O interface  111   a ))) to determine the touch location of front tip interface component  421   a  of stylus  400   a  along input surface input component  110   a  of I/O interface  111   a . Therefore, signal TS may be adjusted by the non-linearity of front tip stylus circuitry  426   a  at or near a node  111   an  and that adjustment (e.g., as harmonics) may be detected as signal RS by that node  111   an.    
     When a frequency may be transmitted through a trace of the mutual capacitance sensor array, such as by signal TS along one or more array trace columns  111   ac , the signal may drive a current back and forth through non-linear electrical circuitry  423   a  of front tip stylus circuitry  426   a  (e.g., through one or more non-linear electrical elements, such as through at least one diode  422   a ) when user U holding body  417   a  of stylus  400   a  positions front tip interface component  421   a  of stylus  400   a  proximate at least one of the array trace columns. Such driving of current back and forth through non-linear electrical circuitry  423   a  may enable front tip interface component  421   a  to see a modulated version of signal TS rather than a pure version of signal TS because front tip stylus circuitry  426   a  may be loaded by a non-linear bias, such that current may pass through front tip stylus circuitry  426   a  more easily in one direction but may be clipped in the other direction for providing a harmonic. For example, when front tip stylus circuitry  426   a  includes a single diode  422   a , a second harmonic of signal TS may be provided by front tip interface component  421   a . Therefore, when such a stylus  400   a  may be known to be available to a user of device  100 , device  100  may be configured (e.g., via any suitable application and/or algorithm(s) or control circuitry for handling I/O interface  111   a ) to look for a second harmonic of signal TS along one or some or each array trace row  111   ar  (e.g., by signal RS) for determining the location of stylus  400   a , where the amount of second harmonic that may be detected for each row or node  111   an  may depend on how close that row or node may be to front tip interface component  421   a  of stylus  400   a . Such a second harmonic may be generated by the rectification by the diode of the transmit voltage signal TS, capacitively divided down. A divider (e.g., capacitor divider) may be provided by system  1 , as may be made up of a capacitance of front tip interface component  421   a  of stylus  400   a  to the transmit plane of sensor layer  110   b  or otherwise of I/O interface  111   a  versus the impedance of front tip stylus circuitry  426   a  (e.g., of diode  422   a ), which may include its junction capacitance. Front tip interface component  421   a  may be configured to have adequate effective capacitance for passive location using projective capacitance, such as, for example, an effective capacitance of 200 femtofarads or any other suitable magnitude. 
     Once a charge on a transmit plane of I/O interface  111   a  (e.g., signal TS) may be seen to be modulated at a harmonic (e.g., a second harmonic (e.g., by I/O interface circuitry  411   a  of stylus  400   a )), I/O interface  111   a  may be configured to act as a transmitter of that harmonic. Such a harmonic of a transmit signal TS, as may be effected by non-linearity of front tip stylus circuitry  426   a , may be unique compared to any adjustment or effect that may be caused by a direct touch or near touch by user U (e.g., by a finger of user U) at I/O interface  111   a , such that device  100  may be configured to distinguish between the two accordingly. For example, while a user&#39;s finger touch may be operative to steal some of an electric field generated by a transmit signal, a harmonic generated by front tip stylus circuitry  426   a  of stylus  400   a  may be specifically different and unique, such that device  100  may be configured to detect and use such passive signal harmonics, for example, and also to reject any detected finger user touches, in order to determine an accurate location of stylus  400   a . For example, when front tip stylus circuitry  426   a  includes a single diode  422   a , a second harmonic of signal TS may be provided by front tip interface component  421   a , such that when a signal (e.g., signal TS) is transmitted by device  100  along I/O interface  111   a  with a particular frequency (e.g., 150 kHz or 70 kHz or 40 kHz), device  100  may be configured to look for a signal (e.g., signal RS) with twice that particular frequency (e.g., 300 kHz or 140 kHz or 80 kHz), where the harmonic may be weaker than the signal at the fundamental frequency (e.g., about 20-25 db down from the signal level from a passive stylus), but unique, and with low background at that frequency. Therefore, when such a stylus  400   a  for providing second harmonics may be known to be available to a user of device  100 , device  100  may be configured (e.g., via any suitable application and/or algorithm(s) or control circuitry for handling I/O interface  111   a ) to look for a second harmonic of signal TS by signal RS for determining the location of stylus  400   a , where the amount of second harmonic that may be detected for each row or node  111   an  may depend on how close that row or node may be to front tip interface component  421   a  of stylus  400   a . Signal TS may be transmitted as any suitable signal, such as a sinusoid shaped signal or a trapezoid shaped signal or any other suitably shaped signal whose non-linear distortion or harmonics of any suitable order may be detectable efficiently and/or effectively by any suitable control application(s) and/or algorithm(s) of device  100 . 
     Device I/O interface control of I/O interface  111   a  for identifying and locating such a stylus  400   a  may be specifically configured or tuned for that particular type of stylus, such that it may be effectively operative to initially identify and roughly locate the location of such a stylus (e.g., by effectively enabling rejection of other types of touch detection (e.g., user finger touch)), such as through detection of a non-linear distortion of the transmitted signal or one or more second harmonic signals (e.g., to a pixel or node pitch distance), and then the control (e.g., one or more algorithms or applications) may be configured to switch to a mode specific to that type of detected stylus (e.g., across sensor layer  110   b  or within a particular radius of the initially detected position of the stylus (e.g., for better jitter performance)). For example, an algorithm may be configured to sense for a particular harmonic of a stylus for a particular transmitted signal, and once detected, more intense and/or frequent and/or focused scans may be utilized to detect that particular harmonic along the I/O interface (e.g., as part of a normal scan, attempt to detect a particular harmonic of a particular expected stylus, and then when that particular harmonic is detected, ramp up the scan features to track that particular stylus (e.g., a type of signal driving may be updated (e.g., only traces around the initially detected position of the stylus may be driven (e.g., to reduce signal to noise))). 
     At least one non-linear electrical element or load or rectifier, such as at least one diode  422   a , of non-linear electrical circuitry  423   a  that may be electrically coupled to front tip interface component  421   a  may enable stylus  400   a  to be identified and distinguished from nearby user touches, dragging fingers, palm rests, and/or the like, due to a non-linear load that may generate a non-linear distortion or harmonics (e.g., a second harmonic) at touch pixels near the stylus tip. Each non-linear electrical element may be configured with any suitable characteristics. For example, diode  422   a  may be provided with any suitable characteristics, such as a low capacitance (e.g., low parasitic capacitance), low reverse leakage, and/or low turn on voltage diode. The junction capacitance of such a diode may be configured to be low (e.g., less than 1.0 picofarad and/or less than 50 femtofarads). A reverse leakage current of such a diode may be controlled to be not too high. A Schottky diode, two or more Schottky diodes in series, or a specifically designed diode may be best suited for such a use. In some embodiments, as shown, circuitry  426   a  may also include (e.g., in parallel with non-linear electrical circuitry  423   a ) any suitable resistance circuitry  425   a  (e.g., at least one resistor  424   a ) for any suitable function, including, but not limited to, controlling reverse leakage current of non-linear electrical circuitry  423   a  and/or preventing direct current (“DC”) positive voltage build up at the diode by effectively draining off any DC while maintaining non-linearity of circuitry  426   a . The resistance of resistance circuitry  425   a  (e.g., resistor  424   a ) may be selected in any suitable manner, such as by using a model of the panel, including its stimulation voltage and capacitance to the tip, and the non-linear device model, and optimizing the model. For an embodiment using one or more Schottky diodes for non-linear electrical circuitry  423   a , the optimum may vary, for example, between 4.0-6.0 megaohms, or even no additional leakage may be needed. 
     At least one non-linear electrical element of non-linear electrical circuitry  423   a , such as diode  422   a , may be used to modulate and rectify a voltage on front tip interface component  421   a  and may provide a load (e.g., a capacitance of front tip interface component  421   a  (e.g., effectively)) and resistance circuitry  425   a , such as resistor  424   a , may be used to discharge the capacitance and/or to prevent capacitance from charging up. A high performance and/or low capacitance and/or low voltage Schottky diode (e.g., on an insulating substrate) may be useful for providing such a diode (e.g., diode  422   a  and/or any other appropriate diode described herein), where such a diode may be made of any suitable material(s), including, but not limited to gallium arsenide and/or titanium nitride, which may have a large reverse leakage, but such leakage may be appropriately handled by resistance circuitry (e.g., resistance circuitry  425   a ). In some embodiments, a diode would be useful if it were configured to have a current-voltage characteristic (e.g., an I-V curve) with certain properties, including, but not limited to, one with an abrupt or substantially abrupt non-linearity at some voltage and one that may maintain that voltage by balancing the forward and reverse characteristics. To produce a certain reverse voltage, the diode may be configured with an I-V curve where current may be sufficient to leak out the current pushed into the diode on the forward voltage and/or to keep an operating point in a region that is non-linear. One or more certain materials may be used to provide such a diode with such performance characteristics. Alternatively or additionally, a particular diode may be radiation damaged such that the diode may be operative to leak during use in a stylus, which may obviate any need for resistance circuitry (e.g., resistance circuitry  425   a ). For example, a diode that has a constant reverse current rather than one that is modulated with a first harmonic may provide a useful result and/or may allow for a stylus without resistance circuitry (e.g., resistance circuitry  425   a ), thereby reducing the number of components of the stylus. Additionally or alternatively to radiation damaging a diode for use in a stylus, the diode may be processed in any other suitable manner(s), including, but not limited to, heat processing or damaging and/or radiation processing or damaging in order to configure the diode to perform in an effective manner, such as to increase or change the reverse leakage of the diode (e.g., increase reverse leakage independently of a reverse voltage). 
     Resistance circuitry of front tip stylus circuitry of a stylus (e.g., resistance circuitry  425   a  of front tip stylus circuitry  426   a  of stylus  400   a ) may include one or more resistors or may not be provided at all (e.g., when a diode with effectively increased reverse leakage is utilized by non-linear electrical circuitry  423   a ). Alternatively, such resistance circuitry may include or be provided by any suitable current limiting device, which may be seen as a constant current source. This may be accomplished by providing any suitable current limiting field-effect transistor (“FET”) (e.g., an n-type metal-oxide-semiconductor (“NMOS”) device or depletion mode device) rather than a resistor. Such a device may be configured not to have a gate, but may include SiO 2  or any other suitable element above a dope channel (e.g., a slightly n-type element), for example, such that the total amount of current that flows therethrough may be about 1 microAmpere. This may provide a flat region, such that when the circuitry goes to a high voltage, the channel may disappear. Therefore, in some embodiments, tip stylus circuitry, such as tip stylus circuitry  426   a , may be generated as a single chip (e.g., through very-large-scale integration (“VLSI”)) that may include a diode (e.g., Schottky diode) (e.g., as at least a portion of circuitry  423   a ) and a current limiting FET (e.g., a diode connected depletion mode device (e.g., a device with a gate connected to the drain of the MOSFET), where a diode connected FET may provide the diode action as well as the constant current backward leakage of the tip stylus circuitry) (e.g., as at least a portion of circuitry  425   a ). 
     Although only one diode  422   a  may be shown as provided by non-linear electrical circuitry  423   a , it is to be understood that any suitable other number of non-linear electrical elements may be provided by non-linear electrical circuitry  423   a , which may be of the same type or different type of non-linear electrical element from one another. For example, two diodes may be electrically coupled in series (e.g., an anode of a first diode may be directly electrically coupled to body stylus circuitry  427   a , while the cathode of that first diode may be directly electrically coupled to an anode of a second diode, while the cathode of that second diode may be directly electrically coupled to front tip interface component  421   a  of stylus  400   a ). For example, two or more diodes (e.g., three diodes as shown in  FIG.  6   ) may be coupled in series (e.g., with the anode of a first diode coupled to the cathode of a second diode, etc.) to create an asymmetric (e.g., top to bottom) waveform, and that may provide a second harmonic. However, compared to only a single diode (see, e.g.,  FIG.  2 B ), multiple diodes provided in series (see, e.g.,  FIG.  6   ) may be operative to reduce the parasitic capacitance across the combination. In other words, two or three diodes in series may look electrically like a single diode (e.g., operative to enable extraction of same harmonic by device  100  (e.g., second harmonic)), but with lower capacitance across them. The forward voltage drop across the diodes may also increase, but the reduction in parasitic capacitance may be more significant and/or effective. For example, the parasitic capacitance across two diodes in series may be half that of one diode, but with twice the forward voltage drop. If the drive waveform is configured to be symmetric in voltage (e.g., a square wave, sinusoidal wave, or trapezoidal wave), then there may be no second harmonic in the original field, and a single diode or diode pair connected in the same direction (e.g., if two diodes are coupled in series, such as with the anode of the first diode coupled to the cathode of the second diode) may be provided by non-linear electrical circuitry  423   a  to create an asymmetric (e.g., top to bottom) waveform, and that may provide a second harmonic. A square or trapezoidal stimulation may have all of the odd harmonics, including the third harmonic, in the transmitted field, so it may be preferred to generate a second harmonic from the diode(s) or non-linear electrical circuitry  423   a . A sinusoidal drive may not have any third harmonic, so back to back diodes or other symmetric non-linear electrical circuitry  423   a  could be used, which may generate odd harmonics that could be detected. In some embodiments where back to back diodes or other symmetric non-linear electrical circuitry is used, resistance circuitry of the tip stylus circuitry including such non-linear electrical circuitry may not be provided or utilized (e.g., as one diode may conduct in a forward direction and one may conduct in a backward direction). 
     As another example, two or more diodes may be electrically coupled in parallel (e.g., an anode of a first diode may be directly electrically coupled to body stylus circuitry, while the cathode of that first diode may be directly electrically coupled (or via a switch) to a tip interface component, and a cathode of a second diode may be directly electrically coupled to body stylus circuitry, while the anode of that second diode may be directly electrically coupled (or via a switch) to the tip interface component (see, e.g.,  FIG.  4   )). Such parallel diodes may be operative to configure the tip stylus circuitry (e.g., non-linear electrical circuitry  423   c  of tip stylus circuitry  426   c  of  FIG.  4   ) to generate third harmonics of the transmitted signal (e.g., as opposed to second harmonics when only one diode is provided within the non-linear electrical circuitry), and device  100  may be configured to detect and handle such third harmonics in a different manner than other harmonics of other stylus types. 
     The direction (e.g., forward direction) of a non-linear electrical element, such as at least one diode  422   a , of non-linear electrical circuitry  423   a  with respect to front tip interface component  421   a  of stylus  400   a  may be any suitable direction. For example, as shown in  FIGS.  2 - 2 C , anode A of diode  422   a  may be directly electrically coupled to body stylus circuitry  427   a , while cathode C of diode  422   a  may be directly electrically coupled to front tip interface component  421   a  of stylus  400   a . Alternatively, in other embodiments, anode A of diode  422   a  may be directly electrically coupled to front tip interface component  421   a , while cathode C of diode  422   a  may be directly electrically coupled to body stylus circuitry  427   a  (see, e.g., the direction of the diodes of circuitry  436   a ′ of  FIG.  6    or the direction of the diode of circuitry  436   a  of  FIG.  2 C ). In either embodiment, the order of the harmonics generated by front tip stylus circuitry  426   a  with only diode  422   a  within non-linear electrical circuitry  423   a  may be second harmonics, although the phase or polarity of such harmonics may be different between those two embodiments, as may be detected by the projective capacitance circuitry of I/O interface  111   a . Therefore, both embodiments may be utilized by the same or different stylus to enable two different stylus types to be located by I/O interface  111   a , where each stylus type may be associated with one or more specific input characteristics. For example, a tip interface component of a stylus that provides second harmonics with a first phase may be determined by device  100  to have a first stylus identity, while a tip interface component of a stylus that provides second harmonics with a second phase different than the first phase may be determined by device  100  to have a second stylus identity different than the first stylus identity, and different stylus identities may be handled by device  100  in any suitable one or more different ways. For example, processor  102  may utilize a specific detected stylus identity (or an absence thereof) in any suitable manner including, but not limited to, accepting or rejecting input from a particular stylus, accepting input from multiple styli and/or from a single stylus, permitting or denying access to a particular functionality of the electronic device, applying a particular stylus profile, restoring one or more settings of the electronic device, notifying a third party that the stylus is in use, applying a setting to the electronic device, applying a setting to a program operating on the electronic device (e.g., which may include updating a user interface on display  112   a  or otherwise of device  100 ), changing a line thickness, color, pattern, erasure, and so on of a graphical object to be rendered by a graphics program of the electronic device, changing a setting of a video game operating on the electronic device, and so on. As shown in  FIG.  2 C , for example, single stylus  400   a  may be provided with two different tip interface components for providing two different stylus identities. For example, as shown, anode A of diode  422   a  of non-linear electrical circuitry  423   a  of front tip stylus circuitry  426   a  may be directly electrically coupled to body stylus circuitry  427   a , while cathode C of diode  422   a  may be directly electrically coupled to front tip interface component  421   a  of stylus  400   a , and, conversely, a cathode C of a diode  432   a  of non-linear electrical circuitry  433   a  of rear tip stylus circuitry  436   a  may be directly electrically coupled to body stylus circuitry  427   a , while an anode A of diode  432   a  may be directly electrically coupled to rear tip interface component  431   a  of stylus  400   a , such that front tip interface component  421   a  may provide second harmonics with a first phase while rear tip interface component  431   a  may provide second harmonics with a second phase. Alternatively, a first number of diodes (e.g., 1) may be provided by non-linear electrical circuitry  423   a  of front tip stylus circuitry  426   a , while a second, different number of diodes (e.g., 2) may be provided by non-linear electrical circuitry  433   a  of rear tip stylus circuitry  436   a  (e.g.,  2  diodes in parallel, as shown by circuitry  423   c  of  FIG.  4   , or 3 diodes in series, as shown by circuitry  436   a ′ of  FIG.  6   ), such that front tip interface component  421   a  may provide second harmonics while rear tip interface component  431   a  may provide different (e.g., third) harmonics. Therefore, device  100  may be configured to determine whether user U may be moving front tip interface component  421   a  of stylus  400   a  along I/O interface  111   a  (e.g., at  FIGS.  2 A and  2 B ) or rear tip interface component  431   a  of stylus  400   a  along I/O interface  111   a  (e.g., at  FIGS.  2 D and  2 E ), such that device  100  may be configured to handle the detection of those different tip interface components in different manners. For example, device  100  may be configured to utilize the detection of front tip interface component  421   a  for enabling generation of a drawing object (e.g., a graphical line) and to utilize the detection of rear tip interface component  431   a  for enabling generation of an erasure object (e.g., removal of any graphical content), such that stylus  400   a  may be utilized within system  1  similarly to a physical pencil that may have a drawing tool on one end and an erasure tool on another end. Although, it is to be appreciated that device  100  may be configured to handle different stylus identifies in any suitable different manners. In some embodiments, different tip interface components (e.g., on opposite ends of the same stylus or on different fingers of a glove or on different styli or accessories altogether) may include different bleed resistors (e.g., different resistance circuitries of the different tip interface components). As the bleed resistor is changed, the timing of the second harmonic may change, and may be detectable as a relative phase change of the second harmonic relative to the first harmonic. One use for such phase change detection may be to use a force sensitive resistor to change the resistance, thus, for example, enabling a tip force to be estimated (e.g., as may be described with respect to circuitry  426   c  of stylus  400   c  of  FIG.  4   ). 
     Therefore, stylus  400   a  may be configured to operate as a semi-passive and/or non-linear stylus. A semi-passive stylus may be a stylus without an active transmitter, such as a stylus that may be configured to react to the incident field but that may not be a simple linear probe like a user&#39;s finger or a conductive rod. Stylus  400   a  may be provided at a very low cost, as it may not require any internal power source and may not require any direct coupling or communication of any wired/wireless communication interface data  56  with device  100 . Stylus  400   a  may provide improved performance over a passive stylus on a projected capacitance input device by being able to be distinguished from direct user touch events (e.g., unintentional user touch events). Non-linearity of stylus  400   a  may double (or otherwise provide any suitable multiple of) a modulation frequency (e.g., a fundamental frequency) of a transmitted signal TS (e.g., from 200 kHz to 400 kHz (see, e.g.,  FIG.  6 D , from a first harmonic  671  to a second harmonic  673 )) such that many cycles of non-linearity may be detected, such that noise may be reduced by requiring detection of a harmonic multiple times within multiple cycles or just once in a single cycle. 
     In addition to use with I/O interface  111   a  when configured to provide mutual capacitance sensing, stylus  400   a  may also be configured to be used with I/O interface  111   a  when configured to provide self-capacitance sensing. For example, as shown in  FIGS.  2 F and  2 G , when providing self-capacitance sensing, each pixel or pad of an array of I/O interface  111   a  (e.g., first pad  111   ap   1  and second pad  111   ap   2 ) may be driven by its own signal TS of its own transmitter circuitry T and an effected signal RS may be detected by any suitable receiver circuitry R. In the environment of self-capacitive sensing, the current taken to drive the pixels may be a non-linear function of the voltage driven, and can thus be distinguished from linear effects, such as a nearby finger or palm. Self-capacitive sensing may be combined with mutual capacitive sensing, for example, by driving a voltage on an electrode and monitoring both the current into that node and current into nearby nodes that are held at a voltage. 
     Another stylus  400   b , as shown in  FIGS.  3 - 3 C  may include stylus I/O circuitry  411   b  that may include body stylus circuitry  427   b  that may be electrically coupled to front tip stylus circuitry  426   b  and/or to rear tip stylus circuitry (not shown). Body stylus circuitry  427   b  may be any suitable circuitry that may be operative to be electrically coupled (e.g., capacitively coupled) to user U when user U is holding stylus  400   b  about at least a portion of body portion  417   b . As shown in  FIG.  3   , for example, body stylus circuitry  427   b  may be at least one conductive wire extending along at least a portion of a length of body portion  417   b  of stylus  400   b , which may be insulated by any suitable insulation  428   b . Alternatively, body stylus circuitry  427   b  may be provided by a conductive (e.g., copper) tape along a portion of body  417   b , where such tape may be positioned under any suitable insulation, such as a finger pad of any suitable material. Any suitable housing  401   b  may be provided to protect body stylus circuitry  427   b , such as a plastic housing. In some embodiments, such a housing may be operative to provide insulation  428   b . Additionally or alternatively, at least a portion of body stylus circuitry  417   b  may be at least partially exposed via housing  401   b  and/or insulation  428   b  for enabling direct contact by user U. When user U is holding stylus  400   b  about and/or along a portion of body  417   b , a capacitance or user-handle capacitor UHC may be inherently formed (e.g., as shown in  FIG.  3 C ). The capacitance of user-handle capacitor UHC may be large enough to pass the desired signal from the tip, but not so large as to allow large transients from electrostatic discharge events to pass. For example, the capacitance of user-handle capacitor UHC may be any suitable capacitance, such as a capacitance in the range of 1.0 picofarad to 10.0 picofarads. 
     Stylus I/O circuitry  411   b  may include a front tip interface component  421   b  that may provide at least a portion of front tip portion  415   b . Front tip interface component  421   b  may be the portion of stylus  400   b  configured to directly interface with device I/O interface  111   a . For example, front tip interface component  421   b  may be formed from any suitable material, including, but not limited to, silicone, rubber, fluoro-elastomer, plastic, nylon, conductive or dielectric foam, metal (e.g., brass (e.g., a brass ball with a dielectric coating (e.g., a thin coating with a high dielectric constant))), or any other suitable material or combination of materials. In this manner, drawing of front tip interface component  421   b  across input surface  110   a  may not cause damage to input surface  110   a  or layers applied to input surface  110   a , such as, but not limited to, anti-reflective coatings, oleophobic coatings, hydrophobic coatings, cosmetic coatings, ink layers, and the like. Front tip interface component  421   b  can be configured to be removably attached to body  417   b , such as via threadings/screws, detents and/or recesses, interference-fit or snap-fit, and/or magnetic attraction, and/or the like, and electrically coupled capacitively, such as through a pogo-pin, spring, and/or the like. Transit of any stylus electric field may be provided from front tip interface component  421   b  and not from other portions of stylus I/O circuitry  411   b . Like component  421   a , front tip interface component  421   b  may be any suitable shape, such as a sphere or hemisphere, of any suitable size. For example, in some particular embodiments, front tip interface component  421   b  may be provided as a ball (e.g., a solder ball and/or brass ball) of any suitable diameter, such as 2 millimeters in diameter. Front tip interface component  421   b  may be configured to provide the same footprint area (e.g., tip field intersection area (e.g., of charge)) on input surface  110   a  no matter the angle of axis  120  with respect to a plane of input surface  110   a . The size of front tip interface component  421   b  may be made as small as possible to enable precise localization of front tip portion  415   b  with respect to device I/O interface  111   a.    
     Front tip stylus circuitry  426   b  may be positioned between and electrically coupled to each one of front tip interface component  421   b  and a portion (e.g., a front end) of body stylus circuitry  427   b . Front tip stylus circuitry  426   b  may be configured as any suitable circuitry that may be operative to modulate a capacitance (e.g., an effective capacitance) at front tip interface component  421   b  when user U is holding body  417   b  of stylus  400   b  such that front tip interface component  421   b  of stylus  400   b  may be stimulated by a device stimulus that may be generated by device I/O circuitry of device I/O interface  111   a  of electronic device  100 . For example, front tip stylus circuitry  426   b  may include any suitable switch circuitry  423   b  that may be electrically coupled (e.g., in series) between front tip interface component  421   b  and body stylus circuitry  427   b . Switch circuitry  423   b  may include any suitable number of any suitable type(s) of switch element(s)  422   b , such as a high impedance switch, such as a field-effect transistor (“FET”) (e.g., a metal-oxide-semiconductor field-effect transistor (“MOSFET”)). Additionally, as shown, front tip stylus circuitry  426   b  may include any suitable microcontroller  402   b  powered by any suitable power supply  408   b  (e.g., a low frequency, very low power battery operated circuit) for switching switch element(s)  422   b  between an open state where front tip interface component  421   b  and body stylus circuitry  427   b  are not electrically coupled and a closed state where front tip interface component  421   b  and body stylus circuitry  427   b  are electrically coupled by switch element  422   b . Microcontroller  402   b  may be configured (e.g., programmed) to switch (e.g., open or close) switch element  422   b  according to a particular pattern (e.g., a micro application  403   b ) or according to a selected one of two or more patterns that may be implemented by microcontroller  402   b . Front tip stylus circuitry  426   b  may be provided as a very low power circuit that may modulate the effective capacitance TC of front tip interface component  421   b  of stylus  400   b  according to a particular pattern. Front tip interface component  421   b  may be configured to have adequate effective capacitance for passive location using projective capacitance, such as, for example, an effective capacitance of 200 femtofarads or any other suitable magnitude. In some embodiments, rather than being powered by power supply  408   b  local to stylus  400   b , controller  402   b  may be powered by any suitable external stimulation (e.g., device I/O circuitry and/or a user holding the stylus). 
     One, some, or each available pattern may be operative to enable device  100  to distinguish stylus  400   b  from a direct user touch event (e.g., by a finger or palm event by user U on I/O interface  111   a ), as a pattern may be detected by receive signal RS at one or more nodes  111   an  (e.g., of  FIG.  3 A  for mutual capacitance) or pads  111   ap  (e.g., pad  111   ap   3  of  FIGS.  3 B and  3 C  for self-capacitance) in response to transmitted signal TS being effected by the pattern-modulated effective capacitance of front tip interface component  421   b , where that pattern may be a pattern that may not be replicated by user U on its own (e.g., without front tip stylus circuitry  426   b ). As an example, an exemplary pattern may be a Barker sequence followed by a digital code, where only the bits in the trailing digital code may change. A reason to have a low frequency pattern may be to minimize the power used by the switching circuit. Therefore, stylus  400   b  may be provided as a low power, semi-permanent battery, switched stylus. No other circuitry may be provided by stylus  400   b , such that it may be made at a low cost and with a very low powered battery that may be configured to enable stylus  400   b  to function properly for many years without replacement. In some embodiments, the battery may be configured for any suitable duration of use, such as in a range of 5-50 milliamp hours. In some embodiments, any suitable input component may also be provided by stylus  400   b  to enable user U to select a particular one of many patterns that may be available to front tip stylus circuitry  426   b , such that a particular pattern may be detected by device  100  and a particular functionality may be carried out by device  100  that may be associated with that particular pattern (e.g., device  100  may be configured to utilize the detection of front tip interface component  421   b  with a first pattern-modulated effective capacitance for enabling generation of a red drawing object (e.g., a red graphical line) and to utilize the detection of front tip interface component  421   b  with a second pattern-modulated effective capacitance for enabling generation of a green drawing object (e.g., a green graphical line), such that stylus  400   b  may be utilized within system  1  similarly to a physical multi-colored pen that may selectively output one of various ink colors. Although, it is to be appreciated that device  100  may be configured to handle different patterns as different stylus identifies in any suitable different manners. 
     Device I/O interface control of I/O interface  111   a  for identifying and locating such a stylus  400   b  may be specifically configured or tuned for that particular type of stylus and/or one, some, or each pattern available to that stylus, such that it may be effectively operative to initially identify and roughly locate the location of such a stylus (e.g., by effectively enabling rejection of other types of touch detection (e.g., user finger touch or other patterns)), such as through detection of a particular pattern, and then the control (e.g., one or more algorithms or applications) may be configured to switch to a mode specific to that type of detected stylus (e.g., across sensor layer  110   b  or within a particular radius of the initially detected position of the stylus (e.g., for better jitter performance)). For example, an algorithm may be configured to sense for a particular pattern of a stylus for a particular transmitted signal, and once detected, more intense and/or frequent and/or focused scans may be utilized to detect that particular pattern along the I/O interface (e.g., as part of a normal scan, attempt to detect a particular pattern of a particular expected stylus, and then when that particular pattern is detected, ramp up the scan features to track that particular pattern (e.g., a type of signal driving may be updated (e.g., only traces around the initially detected position of the stylus may be driven (e.g., to reduce signal to noise))). In an embodiment where a pattern may be a Barker sequence followed by a digital code, the Barker sequence itself and the detection thereof may not need to change. 
     Therefore, stylus  400   b  may be configured to provide a switch that may be modulated at a relatively low frequency, and/or that may be driven by a low power circuit that may be similar to that of an electronic watch, while a projective capacitive input device of I/O interface  111   a  may be configured to seek and/or detect a signal modulated by a changing load of stylus  400   b  (e.g., using a matched filter). Stylus  400   b  may be a very low-power, semi-permanent battery powered stylus that may be provided at a very low cost, as it may not require a substantial internal power source and may not require any direct coupling or communication of any wired/wireless communication interface data  56  with device  100 . Stylus  400   b  may provide improved performance over a passive stylus on a projected capacitance input device by being able to be distinguished from direct user touch events (e.g., unintentional user touch events). Although not shown, single stylus  400   b  may be provided with two different tip interface components, like stylus  400   a , for providing two different stylus identities. For example, switch circuitry  423   b  of front tip stylus circuitry  426   b  may be operative to generate a first pattern, while switch circuitry of a rear tip stylus circuitry may be operative to generate a second pattern different than the first pattern. Additionally or alternatively, an input component of stylus  400   b  may be operative to adjust the type of pattern generated by its switch circuitry from a first pattern to a second pattern different than the first pattern. 
     Yet another stylus  400   c , as shown in  FIG.  4   , for example, may be similar to stylus  400   a , except as described herein. As shown, stylus  400   c  may include stylus I/O circuitry  411   c  that may be similar to stylus I/O circuitry  411   a  and may be operative to be stimulated only by external stimulus, such as a device stimulus that may be generated by device I/O circuitry of device I/O interface  111   a  of electronic device  100  and/or by user U when holding stylus  400   c , whereby that stimulation of stylus I/O circuitry  411   c  may be operative to enable stylus I/O circuitry  411   c  to provide any suitable stylus electric field that may then be detected by device  100  for estimating the location of stylus  400   c . Stylus  400   c  may include a barrel or handle or body portion  417   c  extending between a front tip portion  415   c  and a rear tip portion (not shown), where body portion  417   c  may be configured to be held by user U as the user may slide a tip portion of stylus  400   c  across input surface  110   a  of device I/O interface  111   a  of device  100 . 
     Stylus I/O circuitry  411   c  may include body stylus circuitry  427   c  that may be electrically coupled to front tip stylus circuitry  426   c  and/or to rear tip stylus circuitry (not shown). Body stylus circuitry  427   c  may be any suitable circuitry that may be operative to be electrically coupled (e.g., capacitively coupled) to user U when user U is holding stylus  400   c  about at least a portion of body portion  417   c . As shown in  FIG.  4   , for example, body stylus circuitry  427   c  may be at least one conductive wire extending along at least a portion of a length of body portion  417   c  of stylus  400   c , which may be insulated by any suitable insulation  428   c . Alternatively, body stylus circuitry  427   c  may be provided by a conductive (e.g., copper) tape along a portion of body  417   c , where such tape may be positioned under any suitable insulation, such as a finger pad of any suitable material. Any suitable housing  401   c  may be provided to protect body stylus circuitry  427   c , such as a plastic housing. In some embodiments, such a housing may be operative to provide insulation  428   c . Additionally or alternatively, at least a portion of body stylus circuitry  427   c  may be at least partially exposed via housing  401   c  and/or insulation  428   c  for enabling direct contact by user U. When user U is holding stylus  400   c  about and/or along a portion of body  417   c , a capacitance or user-handle capacitor (e.g., UHC (not shown in  FIG.  4   )) may be inherently formed. The capacitance of such a user-handle capacitor may be relatively large compared to a panel to tip capacitance (e.g., electric field response capacitances (e.g., capacitances SDC) between front tip interface component  421   c  and each one of array trace row  111   ar  and array trace column  111   ac  of one or more nodes  111   an  proximate front tip interface component  421   c  when stylus  400   c  is used with device  100 ), but not so large that electrostatic discharges would be likely to damage the device. Stylus I/O circuitry  411   c  may include a front tip interface component  421   c  that may provide at least a portion of front tip portion  415   c . Front tip interface component  421   c  may be the portion of stylus  400   c  configured to directly interface with device I/O interface  111   a . For example, front tip interface component  421   c  of stylus  400   c  may be similar to front tip component  421   a  of stylus  400   a.    
     Front tip stylus circuitry  426   c  may be positioned between and electrically coupled to each one of front tip interface component  421   c  and a portion (e.g., a front end) of body stylus circuitry  427   c . Front tip stylus circuitry  426   c  may be configured as any suitable circuitry that may be operative to provide a non-linear load between body stylus circuitry  427   c  and front tip interface component  421   c  when user U is holding body  417   c  of stylus  400   c  such that front tip interface component  421   c  of stylus  400   c  may be stimulated by a device stimulus that may be generated by device I/O circuitry of device I/O interface  111   a  of electronic device  100 . For example, front tip stylus circuitry  426   c  may include any suitable non-linear electrical circuitry  423   c  that may be electrically coupled (e.g., in series) between front tip interface component  421   c  and body stylus circuitry  427   c . Non-linear electrical circuitry  423   c  may include any suitable number of non-linear electrical sub-circuitries (e.g., in parallel), such as non-linear electrical sub-circuitry  422   c ′ and/or non-linear electrical sub-circuitry  432   c ′, each of which may include any suitable number and type(s) of non-linear electrical elements. For example, as shown, non-linear electrical sub-circuitry  422   c ′ may include at least one diode  422   c , and non-linear electrical sub-circuitry  432   c ′ may include at least one diode  432   c . One, some, or each diode of non-linear electrical circuitry  423   c  (e.g., diode  422   c  and/or diode  432   c ) may be any suitable type of diode, such as a Schottky diode, a transistor in diode configuration (e.g., a diode connected transistor), and/or the like. In some embodiments, one or each non-linear electrical sub-circuitry of non-linear electrical circuitry  423   c  may include any suitable number (e.g., two or three or four or more) of diodes that may be coupled together in series (e.g., a cathode of one diode may be coupled to an anode of a next diode and/or the like). Alternatively, as shown, only a single diode may be provided by each non-linear electrical sub-circuitry, where an anode of diode  422   c  may be electrically coupled to body stylus circuitry  427   c  and where a cathode of diode  422   c  may be electrically coupled to front tip interface component  421   c  via any suitable switch circuitry  429   c ′ that may be electrically coupled (e.g., in series) between front tip interface component  421   c  and non-linear electrical sub-circuitry  422   c ′, and/or where a cathode of diode  432   c  may be electrically coupled to body stylus circuitry  427   c  and where an anode of diode  432   c  may be electrically coupled to front tip interface component  421   c  via any suitable switch circuitry  439   c ′ that may be electrically coupled (e.g., in series) between front tip interface component  421   c  and non-linear electrical sub-circuitry  432   c ′. Switch circuitry  429   c ′ may include any suitable number of any suitable type(s) of switch element(s)  429   c , and switch circuitry  439   c ′ may include any suitable number of any suitable type(s) of switch element(s)  439   c , where, for example, one, some, or each switch element may be a high impedance switch, such as a field-effect transistor (“FET”) (e.g., a metal-oxide-semiconductor field-effect transistor (“MOSFET”)) or any other suitable switch that may be controlled in any suitable manner (e.g., by a user input button (e.g., via aperture  416 ) and/or any other suitable pressure or force or the like). Any switch of tip stylus circuitry  426   c  may be a force or pressure sensitive switch (e.g., a switch may close if more than a certain threshold amount of force is applied to the switch (e.g., switch  429   c  may be configured to be open unless at least 10 grams of force is applied thereto (e.g., unless a user presses tip interface component  421   c  against device  100  with at least 10 grams of force) and/or switch  439   c  may be configured to be open unless at least 20 grams of force is applied thereto (e.g., unless a user presses tip interface component  421   c  against device  100  with at least 20 grams of force) and/or the like). Additionally or alternatively, any switch of tip stylus circuitry  426   c  may be a mechanical switch that may be opened or closed by a user pressing or depressing a user interface button (e.g., via an aperture  416 ) or via any other suitable user action. 
     Therefore, like stylus  400   a , stylus  400   c  may be operative to provide at least two different stylus identities. For example, due to diode  422   c  being flipped with respect to diode  432   c , such that front tip interface component  421   c  may provide second harmonics with a first phase when switch  429   c  is closed and when switch  439   c  is open whereby diode  422   c  but not diode  432   c  is electrically coupled between body stylus circuitry  427   c  and front tip interface component  421   c , and/or such that front tip interface component  421   c  may provide second harmonics with a second phase different than the first phase when switch  429   c  is open and when switch  439   c  is closed whereby diode  432   c  but not diode  422   c  is electrically coupled between body stylus circuitry  427   c  and front tip interface component  421   c , and/or such that front tip interface component  421   c  may provide no second harmonics when each one of switches  429   c  and  439   c  is open whereby none of diodes  422   c  and  432   c  is electrically coupled between body stylus circuitry  427   c  and front tip interface component  421   c . Alternatively, front tip interface component  421   c  may provide second harmonics when only one of switch  429   c  and switch  439   c  is closed and when the other one of switch  429   c  and switch  439   c  is open, whereby only a single one of diode  422   c  and diode  432   c  is electrically coupled between body stylus circuitry  427   c  and front tip interface component  421   c , or front tip interface component  421   c  may provide different (e.g., third) harmonics when each one of switch  429   c  and switch  439   c  is closed, whereby each one of diodes  422   c  and  432   c  may be electrically coupled between body stylus circuitry  427   c  and front tip interface component  421   c , or front tip interface component  421   c  may provide no second harmonics or third harmonics when each one of switches  429   c  and  439   c  is open, whereby none of diodes  422   c  and  432   c  is electrically coupled between body stylus circuitry  427   c  and front tip interface component  421   c . Therefore, device  100  may be configured to determine whether user U may be moving front tip interface component  421   c  of stylus  400   c  along I/O interface  111   a  with only non-linear electrical sub-circuitry  422   c ′ electrically coupled thereto by switch circuitry  429   c ′, or with only non-linear electrical sub-circuitry  432   c ′ electrically coupled thereto by switch circuitry  439   c ′, or with each one of non-linear electrical sub-circuitry  422   c ′ and non-linear electrical sub-circuitry  432   c ′ electrically coupled thereto by switch circuitry  429   c ′ and switch circuitry  439   c ′, or with no non-linear sub-circuitry electrically coupled thereto by any switch circuitry, such that device  100  may be configured to handle the detection of those different tip interface components in different manners. Therefore, use of one or more switching circuitries may be utilized to alter the stylus identity of tip interface component  421   c  of stylus  400   c  (e.g., between different harmonics and/or between different phases) rather than utilizing different tip interface components (e.g., as described above with respect to tip interface components  421   a  and  431   a  of stylus  400   a ). 
     In some embodiments, as shown, circuitry  426   c  may also include (e.g., in parallel with non-linear electrical circuitry  423   c ) any suitable resistance circuitry  425   c  (e.g., at least one resistor  424   c  (e.g., any suitable force-sensing resistor (e.g., as shown) or any other suitable resistor)) for any suitable function, including, but not limited to, controlling reverse leakage current of non-linear electrical circuitry  423   c  and/or preventing DC positive voltage build up at the diode by effectively draining off any DC while maintaining non-linearity of circuitry  426   c . In some embodiments, such as similarly to resistance circuitry  425   a  of stylus  400   a , the resistance of resistance circuitry  425   c  (e.g., resistor  424   c ) may be selected in any suitable manner, such as by using a model of the panel, including its stimulation voltage and capacitance to the tip, and the non-linear device model, and optimizing the model. For an embodiment using one or more Schottky diodes for non-linear electrical circuitry  423   c , the optimum may vary, for example, between 4.0-6.0 megaohms, or even no additional leakage may be needed. 
     Any switch described herein as may be provided by any stylus or accessory may be provided in a handle portion, such as behind any diodes or resistors or non-linear electrical circuitry or tip stylus circuitry. Such a switch may be operative to break a DC path between them, which may effectively turn off non-linearity because a DC voltage may build up across the diode(s), and the reverse bias may not allow any current to flow. This may be used as a signal to (e.g., detectable by) the sensor circuitry of I/O interface  111   a  of device  100 , or to “break” or lift the pen. Additionally or alternatively, this may be done with a switch that may turn on only when pressure is applied to the tip of the stylus/accessory, which may enable a “make/break” on force rather than on estimated Z-height (e.g., as mentioned herein). 
     Yet another accessory  400   d , as shown in  FIG.  5   , for example, may be similar to stylus  400   a  or any other stylus of this disclosure, except as described herein. Accessory  400   d  may be configured with an accessory housing  401   d  of any suitable structure, such as a glove, as shown, or any other accessory wearable or otherwise usable by a user for interacting with electronic device  100 . Accessory  400   d  include accessory I/O circuitry  411   d  that may be similar to stylus I/O circuitry  411   a  or stylus I/O circuitry  411   b  and may be operative to be stimulated by external stimulus, such as a device stimulus that may be generated by device I/O circuitry of device I/O interface  111   a  of electronic device  100  and/or by user U when using accessory  400   d  (e.g., when a user&#39;s hand is wearing glove accessory  400   d ) and/or by a small power supply of accessory  400   d , whereby that stimulation of accessory I/O circuitry  411   d  may be operative to enable accessory I/O circuitry  411   d  to provide any suitable accessory electric field that may then be detected by device  100  for estimating the location of accessory  400   d . Accessory  400   d  may include a hollow barrel or finger body portion  417   d  (e.g., of a finger  401   df  of body  401   d ) extending between a front tip portion  415   d  and a rear tip (or open end) portion, where body portion  417   d  may be configured to be worn by user U (e.g., by or about or otherwise on a finger of the user) as the user may slide a tip portion of accessory  400   d  (e.g., a fingertip portion that may electrically expose or otherwise be adjacent front tip interface component  421   d  of accessory  400   d ) across input surface  110   a  of device I/O interface  111   a  of device  100 . 
     Accessory I/O circuitry  411   d  may include body accessory circuitry  427   d  that may be electrically coupled to front tip accessory circuitry  426   d . Body accessory circuitry  427   d  may be any suitable circuitry that may be operative to be electrically coupled (e.g., capacitively coupled) to user U when user U is wearing accessory  400   d  (e.g., body portion  417   d  of finger  401   df ) about a portion or against a portion (e.g., finger (e.g., fingertip)) of user U. As shown in  FIG.  5   , for example, body accessory circuitry  427   d  may be at least one conductive pad extending across a hollow of body portion  417   d  of finger  401   df  for being contacted by a user&#39;s finger and/or a ring like conductive structure operative to be worn about a user&#39;s finger. Any suitable housing  401   d  of any suitable material(s) may be provided to protect body accessory circuitry  427   d . When user U is wearing accessory  400   d , a capacitance or user-handling capacitor (e.g., UHC) may be inherently formed. The capacitance of such a user-handling capacitor may be relatively large compared to a panel to tip capacitance (e.g., electric field response capacitances (e.g., capacitances SDC) between front tip interface component  421   d  and each one of array trace row  111   ar  and array trace column  111   ac  of one or more nodes  111   an  proximate front tip interface component  421   d  when accessory  400   d  is used with device  100 ), but not so large that electrostatic discharges would be likely to damage the device. Accessory I/O circuitry  411   d  may include a front tip interface component  421   d  that may provide at least a portion of front tip portion  415   d . Front tip interface component  421   d  may be the portion of accessory  400   d  configured to directly interface with device I/O interface  111   a . For example, front tip interface component  421   d  of accessory  400   d  may be similar to front tip component  421   a  of stylus  400   a.    
     Front tip accessory circuitry  426   d  may be positioned between and electrically coupled to each one of front tip interface component  421   d  and a portion (e.g., a front end) of body accessory circuitry  427   d . Front tip accessory circuitry  426   d  may be configured as any suitable circuitry (e.g., similar to circuitry  426   a  and/or circuitry  426   c ) that may be operative to provide a non-linear load between body accessory circuitry  427   d  and front tip interface component  421   d  when user U is wearing body  417   d  of accessory  400   d  such that front tip interface component  421   d  of accessory  400   d  may be stimulated by a device stimulus that may be generated by device I/O circuitry of device I/O interface  111   a  of electronic device  100 . Alternatively, front tip accessory circuitry  426   d  may be configured as any suitable circuitry that may be operative to function similarly to circuitry  426   b  and/or any other tip accessory circuitry described herein. Therefore, while the overall structure of accessory  400   d  may resemble a glove or any other suitable wearable accessory rather than a stylus, accessory  400   d  may be utilized similar to any stylus described herein. 
     As mentioned, and as further shown in  FIGS.  6  and  6 A , sensor layer  110   b  of electronic device  100  may be configured to provide a matrix or array or grid of any suitable number of array trace columns  111   ac  and any suitable number of array trace rows  111   ar , any two of which may intersect to provide a sensing node. Array trace columns  111   ac  may also be referred to herein as transmit electrodes, while array trace rows  111   ar  may also be referred to herein as receive electrodes. In some embodiments, each one of these transmit and receive electrodes may be formed, at least in part, from an optically transparent conductor, such as, but not limited to, metal oxides such as indium-tin oxide and antimony-tin oxide, nanowire patterns formed from silver nanowire, carbon nanotubes, platinum nanowire, gold nanowire, and so on, thin deposits of metal, and the like. Each transmit electrode may provide any suitable capacitance (e.g., C j   xd ) and each receive electrode may provide any suitable capacitance (e.g., C i   xs ). As shown, the transmit electrodes may be provided in an array that may be orthogonal to the receive electrodes (e.g., below the receive electrodes) in a matrix, while the array or matrix of orthogonal transmit electrodes and receive electrodes of sensor layer  110   b  may be provided below or otherwise adjacent (e.g., etched into or layered on or otherwise positioned against) input surface input component  110   a  (e.g., glass). It is to be understood that although various direction and orientational terms, such as “column” and “row,” and “X-” and “Y-” and “Z,” “up” and “down,” “front” and “back,” “left” and “right,” “upper” and “lower,” “top” and “bottom” and “side,” “above” and “below,” “vertical” and “horizontal” and “diagonal,” “length” and “width” and “thickness” and “diameter” and “cross-section” and “longitudinal,” and/or the like, may be used herein, such references are only for convenience, and that no fixed or absolute directional or orientational limitations are intended by the use of these words. If reoriented, different directional or orientational terms may need to be used in their description, but that will not alter their fundamental nature as within the scope and spirit of the subject matter described herein in any way. For example, while an “X-Y” layout may be referenced with respect to I/O component  111   a , a diagonal lattice layout, where there may be no dedicated X- or Y-elements, but where each element may be transmitting or sensing at different times during a scan of the touch screen, may be utilized for enabling use of any stylus or accessory described herein. Thus, references to the details of the described embodiments are not intended to limit their scope. 
     Any suitable electrical signal (e.g., transmit signal) TS, such as any suitable voltage waveforms (e.g., sinusoidal drive or trapezoidal voltages) (e.g., V j   stim ), may be emitted or transmitted on one, some, or each transmit electrode by any suitable transmitter circuitry T of I/O interface  111   a  (e.g., of sensor layer  110   b ). Such a transmit signal TS may drive non-linear circuitry of a stylus (e.g., circuitry  436   a ′ of stylus  400   a ) that may be positioned on input surface  110   a , and such non-linearity may produce harmonics or any other suitable non-linear aspects of transmit signal TS. Any suitable electrical signal (e.g., receive signal) RS, such as any suitable sensed current (e.g., I i   sense ), may be detected by any suitable receiver circuitry R of I/O interface  111   a  (e.g., of sensor layer  110   b ) that may be provided along each one of the receive electrodes or that may be shared and used serially with two or more receive electrodes. As shown, receiver circuitry R may be any suitable circuitry, such as any suitable operational amplifier circuitry (e.g., a current sense amplifier (e.g., with feedback)) and an analog-to-digital converter (“ADC”) that may be operative to digitize a current or other signal that may be sensed on a receive electrode (e.g., receiver circuitry R may be operative to hold other electrodes at virtual ground and utilize a current to voltage amplifier and then digitize the voltage on the receive electrode). Then, any suitable digital signal processing (“DSP”) may be provided by processor  102  and any suitable application  103  running thereon in combination with the circuitry of I/O interface  111   a  (e.g., circuitry T and circuitry R of sensor layer  110   b ) in order to extract any non-linear aspects of the receive signal RS with respect to the transmit signal TS (e.g., to demodulate the second harmonic of a sine wave) and then to estimate a position of the stylus or accessory tip with respect to device  100  (e.g., X-Y location along the surface of input component  110   a ) based on the extracted non-linear aspects. 
     For example, graph  650  of  FIG.  6 B  may be indicative of an exemplary plot over time of an exemplary transmit voltage, such as a voltage transmit signal TS that may be applied by circuitry T to a transmit electrode of sensor layer  110   b  of I/O interface  111   a . Graph  660  of  FIG.  6 C  may be indicative of an exemplary plot over time of an exemplary tip voltage, such as a voltage receive signal RS that may be sensed by circuitry R as provided on a receive electrode of sensor layer  110   b  of I/O interface  111   a  by a tip of a stylus (e.g., tip  431   a  of stylus  400   a  (e.g., with non-linear circuitry  436   a ′)) when the tip may be stimulated by the transmit voltage of graph  650  (if no tip is present, then the transmit electrode may be just a pure capacitance, and the current sensed may be reactively related through the capacitance, and may be out of phase but still similar to the transmit signal (e.g., sinusoidal, not asymmetrically distorted)). Graph  670  of  FIG.  6 D  may be indicative of an exemplary plot of an exemplary magnitude with respect to frequency of an applied voltage (e.g., voltage transmit signal TS of graph  650 ) as sensed by a receive electrode (e.g., voltage receive signal RS of graph  660 ), for example, as may be determined by the DSP of device  100 . For example, as shown, graph  670  may identify a fundamental frequency (e.g., first harmonic)  671  (e.g., at a frequency of 200 kHz (e.g., a fundamental frequency of transmit signal TS)) and a non-linear aspect (e.g., second harmonic)  673  (e.g., at a frequency of 400 kHz (e.g., a multiple of the fundamental frequency of transmit signal TS)). Therefore, the non-linearity of stylus  400   a  may double (or otherwise provide any suitable multiple of) a modulation frequency (e.g., a fundamental frequency) of a transmitted signal TS (e.g., from 200 kHz to 400 kHz (see, e.g.,  FIG.  6 D , from a first harmonic  671  to a second harmonic  673 )) such that many cycles of non-linearity may be detected, such that noise may be reduced by requiring detection of a harmonic or any other suitable non-linear aspect multiple times within multiple cycles or just once in a single cycle. Depiction  680  of  FIG.  6 E  may be indicative of any external element(s) determined (e.g., by DSP1 (e.g., DSP1@1×) of any suitable processing of device  100 ) to be sensed on a surface of input component  110   a  based on any fundamental frequency or first harmonic information (e.g., information of frequency  671  of graph  670 ) for some or each receive electrode of the system, which, as shown, may be indicative of not only a stylus tip by depiction portion  681  but also a portion of a user&#39;s hand by depiction portion  683 , while depiction  690  of  FIG.  6 F  may be indicative of any external element(s) determined (e.g., by DSP2 (e.g., DSP2@2×) of any suitable processing of device  100 ) to be sensed on a surface of input component  110   a  based on any non-linear aspect or multiple (e.g., second) harmonic information (e.g., information of frequency  673  of graph  670 ) for some or each receive electrode of the system, which, as shown, may be indicative of only a stylus tip by depiction portion  691  and not also a portion of a user&#39;s hand. This may create a unique identifier for a stylus with non-linear circuitry that may resolve certain location detection issues, such as disambiguation, merge, and negative pixel. 
     Therefore, one DSP per receive electrode demodulation path may be set to two-times the stimulation frequency (e.g., the frequency of the stimulation transmitted signal TS) in order to identify the location of a stylus with non-linear circuitry (e.g., circuitry providing a second harmonic), which may be used to only identify the location of the stylus and not a user that may not provide any non-linearity. Therefore, a transmitted signal (e.g., stimulation voltage (e.g., a pure tone or only with odd harmonics)) may be provided on one or more transmit electrodes to drive non-linear circuitry of a stylus that may produce at a stylus tip harmonic(s) or any other suitable non-linear aspect(s) of the transmitted signal (e.g., asymmetrical distortion due to a non-linear load (e.g., rectifier (e.g., diode))) that may be received as receive signal(s) on one or more receive electrodes and used through any suitable processing (e.g., DSP) to diagnose harmonics or non-linearity (e.g., by identifying non-linearity in a sense current spectrum (e.g., identifying that a sense current spectrum contains a second order harmonic)) to determine where a tip of the stylus may be located with respect to the electrodes. 
       FIG.  7    is a flowchart of an illustrative process  700  for determining a location of a stylus with non-linear circuitry at an input component of an electronic device (e.g., stylus  400   a  with non-linear circuitry  423   a  at an input component  110   a  of electronic device  100 ). Process  700  may begin at operation  710 , where any suitable transmit signal or voltage waveform (e.g., transmit signal TS) may be emitted or otherwise provided by the electronic device on one, some, or each transmit electrode (e.g., each transmit electrode serially) in any suitable manner (e.g., in any suitable transmit pattern (e.g., the same stimulation waveform may be provided with one of two alternated phases (e.g., 0° or 180°) or not provided at all to different transmit electrodes in any suitable transmit pattern (e.g., according to any multi-stim matrix)). The transmit signal may include waveforms with little or negligible second harmonic or a known second harmonic. For example, the second harmonic may be low, such as about 50 db below the fundamental of the waveform. The transmit signal may be a sinusoidal waveform or a non-sinusoidal waveform. For example, a trapezoidal waveform may be generated or approximated by adding first harmonic and some amount of third harmonic and/or fifth harmonic, and/or the like to a sinusoidal waveform, which may not add to the voltage (e.g., Vmax) of the transmitted waveform but that may increase the fundamental of the waveform, which may increase the non-linear aspect (e.g., second harmonic) that may be generated and detected via a non-linear stylus (e.g., stylus  400   a  with circuitry  426   a ). Therefore, by adding odd harmonics (e.g., generating a waveform that may only have or may only substantially have odd harmonics), we may essentially drive a trapezoidal waveform that may provide a higher fundamental without a higher Vmax, which may obey certain system constraints while also increasing the non-linear aspect (e.g., second harmonic) of the transmit signal that may be detectable by the system through use of a stylus with non-linear circuitry. 
     At operation  720 , process  700  may include the electronic device holding other electrodes (e.g., receive electrodes) at virtual ground (e.g., with op amp circuitry (e.g., current to voltage amplifier)) and digitize (e.g., with an ADC) any current sensed (e.g., a receive signal RS) on the electrodes (e.g., on one, some, or each receive electrode). For example, any suitable receive circuitry R of sensor layer  110   b  of I/O interface  111   a  may be capacitively coupled to a node (e.g., a capacitive sensing node of the array of receive and transmit electrodes) and may use any suitable feedback circuitry to maintain at a constant voltage and/or at virtual ground and may then output a voltage (e.g., tip voltage) to an ADC. While the receive signal(s) RS sensed at operation  720  may generally be sensed on one or more receive electrodes, device  100  may additionally or alternatively be configured to monitor the current on the drive electrodes for determining one or more receive signals RS. For example, a current at a drive electrode may be measured that may include a harmonically driven portion or otherwise non-linearly or asymmetrically distorted portion when a stylus with non-linear circuitry is affecting one or more transmit signal(s) on one or more drive electrodes. At operation  730 , process  700  may include removing any correlated noise on the measured currents (e.g., the received signal(s) RS of the receive electrode(s) (and/or of the drive electrode(s)) of operation  720 ). 
     At operation  740 , process  700  may include extracting (e.g., with the electronic device (e.g., using any suitable DSP) any suitable non-linear aspects of the measured current with respect to the transmitted waveforms. For example, operation  740  may include demodulating a second harmonic of a sinusoidal transmit signal TS of operation  710  from a current receive signal RS sensed at operation  720 . Operation  740  may include carrying out any suitable comparison of a sensed output current on a receive electrode with respect to an input voltage provided on a transmit electrode in order to identify a non-linear aspect (e.g., a second or third or other suitable harmonic or asymmetric distortion or non-linear distortion of the fundamental (e.g., of the transmit signal at the receive signal)). At operation  750 , it may be determined if all transmit patterns for a current time step have been carried out, and, if not, process  700  may return to operation  710  and once again carry out operations  710 - 740  for another transmit pattern for the current time step. However, if all transmit patterns for a current time step have been carried out, process  700  may proceed from operation  750  to operation  760 . In some embodiments, for a particular time step of device  100 , one, some, or each transmit electrode may be modulated (e.g., provided with a transmit waveform TS) one at a time and an output on one, some, or each receive electrode may be measured at operations  710 - 750 . Alternatively, to be more efficient, for a particular time step of device  100 , a correlated pattern (e.g., invertible Hadamard matrix) of transmit electrodes may be modulated (e.g., provided with a transmit waveform TS) and an output on one, some, or each receive electrode may be measured at operations  710 - 750 . However, generally, for a particular time step of device  100 , one or more transmit electrodes may be stimulated (e.g., serially or in various patterns) and receive signal data may be extracted from one or more receive electrodes (and/or drive electrodes) for use in identifying non-linear aspects for determining a location of a non-linear accessory or stylus during that particular time step. At operation  760 , process  700  may include estimating (e.g., using any suitable processing of device  100 ) a position of a tip of an accessory on an input surface of the electronic device for a particular time step of the device using the measurements of operations  710 - 740  for the particular time step. At operation  770 , process  700  may include outputting (e.g., using any suitable processing of device  100 ) an X-Y location estimation for the tip of the accessory for the particular time step, while process  700  may also return to operation  710  and repeat the process for a next time step of the device. Such an output X-Y location estimation for the accessory tip may be utilized (e.g., using any suitable processing and/or other component(s) of device  100 ) in any suitable manner for carrying out or adjusting any suitable functionality of the system, such as for adding graphical object data to a presented display on device  100  or adjusting the position of a cursor on device  100  or selecting an option associated with a graphical object displayed by device  100  at that X-Y location and/or the like. 
     As just one example, operation  760  may include one or more sub-operations, such as operations  761 ,  763 ,  765 ,  767 , and/or  769 . For example, operation  761  may include removing any suitable correlated noise across the receive electrodes (e.g., in addition to or as an alternative to the removal at operation  730 ). For example, in a given time step, multiple receive electrodes may be receiving current or any other signal(s) that may be sensed at operation  720 , such that any or all noise that may be common mode or linearly related between those receive electrodes may be removed (e.g., as an effective procedure to improve signal to noise ratio). At operation  763 , any suitable non-linear residual may be estimated and removed from any suitable electronics of device  100  (e.g., any second harmonic of the fundamental that may be emitted by any electronics of device  100  that may interfere with the accuracy of process  700 ). At operation  765 , the most likely position (e.g., X-Y location) of the tip from the given observed data (e.g., as observed earlier in process  700  for the particular time step (e.g., as may have been adjusted through removal of noise and residuals)) may then be estimated. At operation  767 , a signal strength of any signals of process  700  (e.g., the signal strength of any receive signals RS of operation  720 ) may be extracted to determine the height of the tip from the surface of input surface  110   a . Such a determined height may be used by device  100  to determine whether or not the stylus is touching input surface  110   a  or otherwise determine whether the position of the tip being estimated is a position intended to be identified as an intentional stylus input event (e.g., to determine if the stylus is intended to be used as an input device for drawing a line or if the stylus is not intended to be used as an input device but is rather lifted off the input surface and is being moved to a new location for a new input event). At operation  769 , the estimated position for the particular time step of operation  765  (e.g., if not to be disregarded due to an insufficient signal strength of operation  767 ) may be temporally filtered using any suitable estimated positions from previous iterations of process  700  for previous time steps. For example, any suitable temporal filter may be configured to provide estimates for where a tip is for a particular time step that may be smoothed out based on earlier estimates for earlier time steps before presenting an estimated location for the current time step for use at operation  770  (e.g., before the estimate is presented to an operating system or specific stylus-position dependent application that may be running on device  100 ). 
     Any suitable process(es) may be carried out (e.g., automatically by any suitable processing/application(s) of device  100 ) in order to estimate the most likely position of the tip of the stylus. For example, the non-linear aspects and/or any other determined information from operations  710 - 763  for a particular time step may be compared to outputs of any suitable model for an array of various possible X-Y locations and then find the model output that compares most favorably to the data determined for the current time step (e.g., using best fit via a least squares method) and then using the X-Y location of that model output as the estimated location of the stylus tip for the current time step. Such a model may be generated in any suitable manner. For example, such a model may be a mathematical model built based on a physics model of capacitance to the tip of the stylus and based on a circuit simulator model (e.g., simulation program with integrated circuit emphasis (“SPICE”) model) of the electronic device. For example, such a physics model may utilize finite element analysis (“FEA”) to physically diagram the interaction between the stylus and the device in order to calculate the expected fields (e.g., location of tip to location of capacitance), which may include a calculation of capacitance between transmit and receive electrodes for every possible position of the stylus tip with respect to the device&#39;s input surface, while such a circuit simulator model may utilize circuitry information about the circuitry (e.g., any suitable non-linear elements) of device  100  and/or of the stylus. The combined mathematical model may then be utilized to generate various sets of outputs, where each set may be indicative of the receive signal RS expected to be received at each device electrode when the tip is at a respective one of the various possible X-Y locations along the device&#39;s input surface. Such sets of model outputs may then be compared to an actual set of outputs by the device as determined at operations  710 - 763  for a particular time step in order to determine the best fit model output set in order to use the X-Y position associated with that best fit model output set as the estimated most likely position of the stylus with respect to device  100  for that particular time step. 
     In some embodiments, a magnitude of the force or pressure exerted by the accessory tip on the input surface may be determined by the electronic device. For example, a phase angle between the fundamental of a transmit signal and a non-linear aspect of a sensed receive signal may be identified and used to determine an amount of pressure exerted by the stylus (e.g., when a signal is demodulated to extract a second harmonic, the in-phase and quadrature (“I&amp;Q”) components and phase angle may be realized by such processing). For example, the resistance of resistance circuitry  425   c  may be selectively adjusted by a user during use of stylus  400   c , which may adjust voltage of tip voltage and/or the phase angle between the fundamental of the transmit signal and the non-linear aspect of the detected receive signal. For example, a strain sensitive or force-sensing or any other suitable resistor  424   c  may be provided by resistance circuitry  425   c  that may adjust the resistance of resistor  424   c  based on how much force or pressure is applied thereto. Therefore, a stylus may be configured such that an amount of force used by the user to press the stylus tip against an input surface of an electronic device may adjust the amount of resistance provided by resistance circuitry (e.g., resistance circuitry in parallel with non-linear circuitry of that stylus). Such resistance adjustment may adjust the voltage of a receive signal and/or the phase angle detected by the electronic device and may be used to estimate the amount of force used by the user and stylus, which may provide yet another input for affecting the functionality of device  100  (e.g., in addition to an estimated location of the stylus (e.g., such that location and force of the stylus may together be used to determine how the device adjusts a device functionality (e.g., draw a light green line at a location or draw a dark green line at the location))). As just one example, an output of the model described with respect to operation  765  may include a phase angle output that may then be associated with a force output or the model may include a force output based on a determined phase angle. 
     In some embodiments, selective or dynamic scanning may be utilized to make process  700  more effective and/or efficient. For example, from one or more previous iterations of process  700  for one or more previous time steps, a previous location of a stylus may be estimated, and such an estimated location may be used to selectively or dynamically limit the electrodes that may be used in a current iteration of process  700  for a current time step (e.g., to only transmit signal(s) on certain transmit electrodes that may be proximate to the earlier estimated location and/or to only sense receive signal(s) on certain receive and/or transmit electrodes that may be proximate to the earlier estimated location), which may speed up processing and/or reduce power consumption for such a process. Different modes of location detection may be used for different types of external inputs, such as direct user touch, stylus with non-linear circuitry (e.g., stylus  400   a ), stylus with pattern generating circuitry (e.g., stylus  400   b ), and/or the like. For example, as shown by  FIG.  6   , a first DSP1 may be used to detect fundamental information of any external element(s) that may be used to determine the location of a user and/or any stylus or accessory (see, e.g., depiction  680  of  FIG.  6 E ), while a second DSP2 may be used to detect non-linear information of any external element(s) that may be used to determine the location of a stylus or accessory with non-linear circuitry (see, e.g., depiction  690  of  FIG.  6 F ). Such different modes may be switched temporally such that each mode may be carried out for a single time step (e.g., in a time slice fashion). The detected location data for external element(s) that may be generated by each mode for a single time step (e.g., data of depiction  680  and data of depiction  690 ) may be utilized together to provide one or more improved location estimates (e.g., for a stylus with non-linear circuitry) and/or to provide a more effective and/or efficient localization process. Additionally or alternatively, such temporally switched modes may allow for the concurrent detection of different styli during a single time step, such as by using a first mode to detect a first non-linear aspect (e.g., a second harmonic or a harmonic with a first phase) and by using a second mode to detect a second non-linear aspect (e.g., a third harmonic or a harmonic with a second phase). 
     It is understood that the operations shown in process  700  of  FIG.  7    are only illustrative and that existing operations may be modified or omitted, additional operations may be added, and the order of certain operations may be altered. While  FIGS.  6 ,  6 A- 6 F, and  7    may be discussed generally with respect to second order harmonic extraction as a particular type of non-linear aspect that may be utilized for stylus localization, it is to be understood that any other suitable type of non-linear aspect may be detected and utilized according to process  700 , such as third order harmonic with respect to a stylus with non-linear circuitry providing two diodes in parallel, for example. 
       FIG.  8    is a flowchart of an illustrative process  800  for using a stylus that may include non-linear circuitry at an input component of an electronic device (e.g., stylus  400   a  with non-linear circuitry  423   a  at an input component  110   a  of electronic device  100 ). Process  800  may begin at operation  802 , where an electrical signal may be transmitted from transmitter circuitry of the input component of the electronic device (e.g., signal TS). At operation  804 , the non-linear circuitry of the stylus may be stimulated with the transmitted electrical signal. At operation  806 , a non-linear load may be provided at the stylus based on the stimulating of operation  804 . At operation  808 , a harmonic of the transmitted electrical signal may be created at the input component of the electronic device based on the non-linear load provided at operation  806 . Then, for example, the created harmonic may be detected with the electronic device and, based on the detecting, a position of the stylus with respect to the input component may be determined. 
     It is understood that the operations shown in process  800  of  FIG.  8    are only illustrative and that existing operations may be modified or omitted, additional operations may be added, and the order of certain operations may be altered. 
       FIG.  9    is a flowchart of an illustrative process  900  for using a stylus that may include switching circuitry at an input component of an electronic device (e.g., stylus  400   b  with switching circuitry  423   b  at an input component  110   a  of electronic device  100 ). Process  900  may begin at operation  902 , where an electrical signal may be transmitted from transmitter circuitry of the input component of the electronic device (e.g., signal TS). At operation  904 , the switching circuitry may be switched according to a pattern (e.g., concurrently with operation  902 ). At operation  906 , based on the switching of operation  904 , the transmitted electrical signal may be modulated according to the pattern. Then, for example, the modulated electrical signal may be detected with the electronic device and, based on the detecting, a position of the stylus with respect to the input component may be determined. 
     It is understood that the operations shown in process  900  of  FIG.  9    are only illustrative and that existing operations may be modified or omitted, additional operations may be added, and the order of certain operations may be altered. 
       FIG.  10    is a flowchart of an illustrative process  1000  for detecting an accessory on an input surface of an input component of an electronic device that includes a matrix of a plurality of transmit electrodes and a plurality of receive electrodes (e.g., for detecting any accessory or stylus  400 - 400   d  on input surface  110   a  of I/O component  111   a  that includes an array of electrodes). Process  1000  may begin at operation  1002 , where a transmit signal may be transmitted on each transmit electrode of at least a subset of the plurality of transmit electrodes (e.g., a transmit signal TS may be transmitted by transmitter circuitry T of device  100 ). At operation  1004 , a receive signal may be sensed on each receive electrode of at least a subset of the plurality of receive electrodes (e.g., a receive signal RS may be sensed by receiver circuitry R of device  100 ). At operation  1006 , data indicative of a non-linear aspect of the transmit signal may be extracted from each sensed receive signal (e.g., as described with respect to operation  740  of process  700 ), and, at operation  1008 , a position of the accessory on the input surface may be estimated based on the extracted data (e.g., as described with respect to operation  760  of process  700 ). 
     It is understood that the operations shown in process  1000  of  FIG.  10    are only illustrative and that existing operations may be modified or omitted, additional operations may be added, and the order of certain operations may be altered. Different transmit signals may be transmitted on different transmit electrodes of at least the subset at operation  1002  (e.g., at the same time or at different times), and data indicative of a non-linear aspect of those transmit signals may be extracted at operation  1006  from the sensed receive signals. 
     Tip components of styli and other accessories described herein may be sensitive to electrostatic discharge. Therefore, various features may be provided for protecting the accessories (e.g., tip components of accessories) against electrostatic discharge (“ESD”). Any tip stylus circuitry of any suitable tip portion may be provided with any suitable ESD protection circuitry for providing ESD protection to the tip stylus circuitry (e.g., to the non-linear electrical circuitry of the tip stylus circuitry). As shown in  FIGS.  11  and  11 A , any suitable accessory or stylus  1100  (e.g., which may be the same as or similar to any one or more of accessories or styli  400 ,  400   a ,  400   b ,  400   c , and  400   d ) may include any suitable tip portion  1115  (e.g., which may be the same as or similar to any one or more of tip portions  415 ,  415   a ,  415   b ,  415   c ,  415   d ,  419 , and  419   a ) that may be removably or fixedly coupled (e.g., physically and/or electrically) to any suitable body stylus circuitry  1127  (e.g., which may be the same as or similar to any one or more of circuitries  427   a ,  427   b ,  427   c , and  427   d ) of any suitable barrel or handle or body portion  1117  (e.g., which may be the same as or similar to any one or more of body portions  417 ,  417   a ,  417   b ,  417   c , and  417   d ) for providing any suitable accessory or stylus I/O circuitry  1111  (e.g., which may be the same as or similar to any one or more of I/O circuitries tip portions  411 ,  411   a ,  411   b ,  411   c , and  411   d ) for use by any suitable user U with any suitable device I/O interface (e.g., device I/O interface  111   a ). Tip portion  1115  may include any suitable tip interface component  1121  (e.g., which may be the same as or similar to any one or more of tip interface components  421   a ,  421   b ,  421   c ,  421   d , and  431   a ) and any suitable tip stylus circuitry  1126  (e.g., which may be the same as or similar to any one or more of tip stylus circuitries  426   a ,  426   b ,  426   c ,  426   d ,  436   a , and  436   a ′). Tip stylus circuitry  1126  may be positioned between and electrically coupled to each one of tip interface component  1121  and a portion (e.g., an end) of body stylus circuitry  1127  (e.g., a ground rod (e.g., of a purely capacitively coupled device)). Tip stylus circuitry  1126  may include any suitable non-linear electrical circuitry  1123  (e.g., which may be similar to any one or more of circuitries  423   a ,  423   b ,  423   c , and  433   a ) that may be electrically coupled (e.g., in series) between tip interface component  1121  and body stylus circuitry  1127 . For example, non-linear electrical circuitry  1123  may include any suitable number of any suitable type(s) of non-linear electrical elements  1122 , such as one or more signaling diodes  1122  (e.g., any suitable type of diode, such as a Schottky diode, a transistor in diode configuration (e.g., a diode connected transistor), and/or the like). Non-linear electrical circuitry  1123  may include any suitable number (e.g., one or two or three or four or more) of non-linear electrical elements  1122  (e.g.,  3 , as shown) that may be coupled together in series (e.g., a cathode of one signaling diode  1122  may be coupled to an anode of a next signaling diode  1122  and/or the like) or in parallel or otherwise (e.g., between a node  1191  and a node  1195 ). Additionally, tip stylus circuitry  1126  may include (e.g., in parallel with non-linear electrical circuitry  1123  (e.g., between node  1191  and node  1195 )) any suitable signaling resistance circuitry  1125  (e.g., which may be the same as or similar to any one or more of circuitries  425   a  and  425   c ). For example, signaling resistance circuitry  1125  may include any suitable number of any suitable type(s) of signaling resistance elements  1124 , such as one or more signaling resistors  1124  that may be coupled together in series (e.g., 3, as shown) or in parallel or otherwise, for any suitable function, including, but not limited to, controlling reverse leakage current of non-linear electrical circuitry  1123  and/or preventing DC positive voltage build up at the diode(s) or other non-linear electrical element(s)  1122  of non-linear electrical circuitry  1123  by effectively draining off any DC while maintaining non-linearity of tip stylus circuitry  1126 . The resistance of resistance circuitry  1125  may be selected in any suitable manner, such as by using a model of the panel, including its stimulation voltage and capacitance to the tip, and the non-linear device model, and optimizing the model. For an embodiment using one or more Schottky diodes for non-linear electrical circuitry  1123 , the optimum may vary, for example, between 4.0-6.0 megaohms, between 4.0-10.0 megaohms, between 4.0-15.0 megaohms, or even no additional leakage may be needed. 
     Moreover, as shown, tip stylus circuitry  1126  may include any suitable ESD protection circuitry  1150  for providing ESD protection to tip stylus circuitry  1126  (e.g., to enable the diode(s) or other non-linear electrical element(s)  1122  of non-linear electrical circuitry  1123  to survive ESD shocks (e.g., to prevent a current that may be generated by an ESD shock from damaging the diode(s) or other non-linear electrical element(s)  1122  of non-linear electrical circuitry  1123  by static electricity flowing thereacross)). For example, ESD protection circuitry  1150  may include any suitable ESD path circuitry  1158 , which may be positioned between and electrically coupled to node  1191  and a node  1199  that may be coupled to body stylus circuitry  1127  (e.g., ESD path circuitry  1158  may be electrically coupled in parallel with non-linear electrical circuitry  1123  and with resistance circuitry  1125 ). For example, ESD path circuitry  1158  may include any suitable number of any suitable type(s) of ESD path elements  1156 , such as one or two or more diodes  1156  in series (e.g., three (e.g., as shown in  FIG.  11   ) or six (e.g., as shown in  FIG.  11 A )) or in parallel or otherwise, for any suitable function, including, but not limited to, providing an ESD path around non-linear electrical circuitry  1123  (e.g., for bleeding at least a portion of an ESD event through a different circuit path than through non-linear electrical circuitry  1123 ). One, some, or each ESD path element  1156  may be any suitable diode, such as a transient-voltage-suppression (“TVS”) diode or transil or thyrector or transorb or TVS array package (e.g., several in one package), which may be configured to standoff several volts under ordinary circumstances but then shunt excess current therethrough when an induced voltage (e.g., an ESD event from a 7,000 volt discharge event or from a 15,000 volt discharge event or from any other suitable discharge event) exceeds an avalanche breakdown potential, thereby suppressing overvoltages above its breakdown voltage, and to reset automatically when the overvoltage goes away, but to absorb much of the transient energy. Therefore, ESD path element(s)  1156  may be configured to divert at least some excess current (e.g., as generated by static electricity) through ESD path circuitry  1158  rather than such current causing damage to non-linear electrical circuitry  1123  by flowing across non-linear electrical element(s)  1122  of non-linear electrical circuitry  1123 . In some embodiments, rather than providing just one ESD path element  1156 , which may protect against certain ESD events but add significant parasitic capacitance (e.g., about 0.1 picofarad), ESD path circuitry  1158  may include two or more ESD path elements  1156  in series, which may decrease or limit the amount of parasitic capacitance (e.g., series capacitance) added and/or may increase the breakdown voltage. In some embodiments, a series capacitance of tip stylus circuitry  1126  may be in the range of 50.0 femtofarads to 200.0 femtofarads. Stylus  1100  may be designed such that the total capacitance through stylus  1100  (e.g., through the tip) may be between 20.0 femtofarads and 500 femtofarads, or at least less than 300 femtofarads, wherein total capacitance through the structure (e.g., through the tip) may be less than 300 femtofarads. 
     In some situations, non-linear electrical element(s)  1122  of non-linear electrical circuitry  1123  may carry most of the current and may breakdown before ESD path element(s)  1156  of ESD path circuitry  1158  detects enough voltage of the ESD event to start shunting excess current therethrough. Therefore, additional circuitry may be provided to enable or better ensure that when an ESD event occurs, at least a large portion of the ESD may travel through ESD path circuitry  1158  rather than through non-linear electrical circuitry  1123 . For example, ESD protection circuitry  1150  may include any suitable ESD resistance circuitry  1152 , which may be positioned between and electrically coupled to node  1195  and node  1199  (e.g., ESD resistance circuitry  1152  may be electrically coupled in series with body stylus circuitry  1127  and the parallel combination of non-linear electrical circuitry  1123  and resistance circuitry  1125 , while ESD resistance circuitry  1152  may also be electrically coupled in parallel with ESD path circuitry  1158 ). For example, ESD resistance circuitry  1152  may include any suitable number of any suitable type(s) of ESD resistance elements  1154 , such as one or more current limiting resistors  1154  (e.g., one (e.g., as shown in  FIG.  11   ) or two or more that may be coupled together in series or in parallel or otherwise (e.g., two sets of three in-series resistors (e.g., 0402 size resistors) in parallel with one another and/or with a single resistor (e.g., an 0805 or 0603 size resistor) (e.g., as shown by an alternative circuitry  1152 ′ in  FIG.  11 A )) or the like), for any suitable function, including, but not limited to, limiting the amount of current (e.g., ESD current) able to pass through non-linear electrical circuitry  1123 . ESD resistance circuitry  1152  (e.g., resistance element  1154  of  FIG.  11   ) may be any suitable size or type with any suitable resistance, such as a resistor with a resistance of 10 kiloohms, 50 kiloohms, 100 kiloohms, 200 kiloohms, 500 kiloohms, anything therebetween, or the like. Without ESD path circuitry  1158 , resistance element(s)  1154  of ESD resistance circuitry  1152  may degrade during an ESD shock event, whereby tip stylus circuitry  1126  may fail after degradation of such resistance element(s)  1154 . However, in combination with ESD path circuitry  1158  in ESD protection circuitry  1150  of tip stylus circuitry  1126 , ESD resistance circuitry  1152  may protect non-linear electrical element(s)  1122  of non-linear electrical circuitry  1123  at least up to the added breakdown voltage of ESD path element(s)  1156  of ESD path circuitry  1158 . ESD resistance circuitry  1152  may be configured to prevent non-linear electrical circuitry  1123  from conducting first in the event it has a breakdown event and to make most of the current flow through ESD path circuitry  1158  during the ESD event as ESD path element(s)  1156  of ESD path circuitry  1158  may break down to a very low resistance in response to a high voltage pulse. ESD resistance circuitry  1152  may be configured such that tip stylus circuitry  1126  may avoid voltage/current degradation during an ESD event. ESD resistance circuitry  1152  may be configured to prevent an ESD strike event from arcing around one, some, or each of the resistance element(s)  1154  of ESD resistance circuitry  1152  and damaging tip stylus circuitry  1126 . In some embodiments, multiple resistance elements  1154  may be provided by ESD resistance circuitry  1152 , such that ESD resistance circuitry  1152  may still provide ESD protection even if one or some of the multiple resistance elements  1154  fail or are damaged. The longer a package of resistor elements provided by ESD resistance circuitry  1152  (e.g., the longer the ESD resistance circuitry), the less likely ESD resistance circuitry  1152  may be to fail (e.g., the less likely it may be arced around). Additionally or alternatively, the bigger a resistor element provided by ESD resistance circuitry  1152 , the less likely that resistor element may be to fail (e.g., fail from just seeing too much current). 
     As shown in  FIG.  11 A , tip stylus circuitry  1126  may be mounted on or otherwise supported by or interconnected by any suitable circuit board  1160  (e.g., for providing any suitable bus or the like, which may be similar to bus  414 ). Circuit board  1160  (e.g., a printed circuit board (“PCB”)) may then be positioned within a housing of the stylus or accessory and electrically coupled to tip interface component  1121  (e.g., at node  1191 ) and to body stylus circuitry  1127  (e.g., at node  1199 ). While  FIGS.  11  and  11 A  may show tip interface component  1121  electrically coupled to tip stylus circuitry  1126  at node  1191  and body stylus circuitry  1127  electrically coupled to tip stylus circuitry  1126  at node  1199  (e.g., to keep oscillating voltages of circuitry  1126  (e.g., of circuitry  1123 ) to be constrained as close to tip interface component  1121  as possible, which may help reduce wobble), it is to be understood that the opposite could be true where tip interface component  1121  may be electrically coupled to tip stylus circuitry  1126  at node  1199  and body stylus circuitry  1127  may be electrically coupled to tip stylus circuitry  1126  at node  1191 . Moreover, as shown in  FIG.  11 A , circuit board  1160  may provide each one of a first (e.g., top) surface  1161  and a second (e.g., bottom) surface  1169 , and different portions of tip stylus circuitry  1126  may be electrically coupled to different surfaces of board  1160 . For example, as shown, non-linear electrical circuitry  1123  may be provided on and electrically coupled to surface  1161  while resistance circuitry  1125  and ESD path circuitry  1158  may be provided on and electrically coupled to surface  1169 . ESD resistance circuitry  1152  may include different resistance elements  1154  on different surfaces or each resistance element  1154  on only one of the surfaces. However, in other embodiments, it is to be understood that non-linear electrical circuitry  1123  and ESD path circuitry  1158  may be provided on the same circuit board surface. Any arrangement of various components of tip stylus circuitry  1126  on various surfaces of circuit board  1160  may be made (e.g., diodes on one side and resistors on another), although a goal may be to keep the net capacitance across the whole circuitry to be as low as possible when the device is in operation, to minimize trace parasitic coupling, to prevent fields from skipping over devices and jumping from one electrode to another in the stack, and/or to reduce stray capacitance. 
     Tip components of styli and other accessories described herein may be configured to be removably or fixedly coupled to a barrel or handle or body portion. As shown in  FIGS.  12  and  12 A , any suitable accessory or stylus  1200  (e.g., which may be the same as or similar to any one or more of accessories or styli  400 ,  400   a ,  400   b ,  400   c ,  400   d , and  1100 ) may include any suitable tip portion  1215  (e.g., which may be the same as or similar to any one or more of tip portions  415 ,  415   a ,  415   b ,  415   c ,  415   d ,  419 ,  419   a , and  1115 ) that may be removably or fixedly coupled (e.g., physically and/or electrically) to any suitable body stylus circuitry  1227  (e.g., which may be the same as or similar to any one or more of circuitries  427   a ,  427   b ,  427   c ,  427   d , and  1127 ) of any suitable barrel or handle or body portion  1217  (e.g., which may be the same as or similar to any one or more of body portions  417 ,  417   a ,  417   b ,  417   c ,  417   d , and  1117 ) for providing any suitable accessory or stylus I/O circuitry  1211  (e.g., which may be the same as or similar to any one or more of I/O circuitries tip portions  411 ,  411   a ,  411   b ,  411   c ,  411   d , and  1111 ) for use by any suitable user U with any suitable device I/O interface (e.g., device I/O interface  111   a ). Tip portion  1215  may include any suitable tip interface component  1221  (e.g., which may be the same as or similar to any one or more of tip interface components  421   a ,  421   b ,  421   c ,  421   d ,  431   a , and  1121 ) and any suitable tip stylus circuitry  1226  (e.g., which may be the same as or similar to any one or more of tip stylus circuitries  426   a ,  426   b ,  426   c ,  426   d ,  436   a ,  436   a ′, and  1126 ). Tip stylus circuitry  1226  may be positioned between and electrically coupled to each one of tip interface component  1221  and a portion (e.g., an end) of body stylus circuitry  1227  (e.g., a ground rod (e.g., of a purely capacitively coupled device)). Tip stylus circuitry  1226  may extend between nodes  1291  and  1299  (e.g., which may be the same as or similar to nodes  1191  and  1199 ) and may be provided on a circuit board  1260  (e.g., which may be the same as or similar to board  1160 ). As shown, tip component portion  1215  may include a tip component housing  1201   a  that may at least partially protect one, some, or each of the components of tip component portion  1215 . For example, tip component housing  1201   a  may at least partially define a tip housing space  1201   as  within which tip interface component  1221  and/or tip stylus circuitry  1226  and/or circuit board  1260  may be at least partially positioned. As shown, tip portion  1215  may also include any suitable conductive compressible component  1270  (e.g., foam or spring (e.g., a preloaded spring)) that may extend between a first end  1271  and a second end  1272 . Tip portion  1215  may also include a conductive pad  1274 . As shown, conductive compressible component  1270  may be positioned within housing space  1201   as  such that first end  1271  of conductive compressible component  1270  may contact or at least face node  1299  of circuitry  1226  (e.g., a node contact of board  1260  or otherwise) and such that second end  1272  of conductive compressible component  1270  may contact or at least face conductive pad  1274 . In some embodiments, a protective cover  1276  (e.g., a polymide film (e.g., KAPTON® by DuPont)) may be provided over an opening at an open end of tip component housing  1201   a , which may retain the contents of space  1201   as  therein (e.g., board  1260 , conductive compressible component  1270 , conductive pad  1274 , etc.) and/or protect such contents against ESD. As shown, body portion  1217  may include a body housing  1201   z  that may at least partially protect one, some, or each of the components of body portion  1217 . For example, body housing  1201   z  may at least partially define a body housing space  1201   zs  within which body stylus circuitry  1227  may be at least partially positioned (e.g., freely or adhered to an interior of body housing  1201   z  via any suitable bonding  1201   b ). Body housing  1201   z  may be defined to have an open end towards which a body point portion  1227   p  of body stylus circuitry  1227  may face. An enclosure or housing of stylus  1200  may be provided by a combination of tip component housing  1201   a  and body housing  1201   z.    
     Tip portion  1215  can be configured to be removably or fixedly coupled to body portion  1217  using any suitable coupling features. For example, any suitable tip coupling feature(s)  1201   ac  may be provided by tip component housing  1201   a  and/or by any other suitable component(s) of tip portion  1215 , and any suitable body coupling feature(s)  1201   zc  may be provided by body housing  1201   z  and/or by any other suitable component(s) of body portion  1217 , and features  1201   ac  and  1201   zc  may interact with one another in any suitable manner for removably or fixedly coupling tip component housing  1201   a  and body housing  1201   z  to one another. For example, features  1201   ac  and  1201   zc  may provide such coupling via threadings/screws, detents and/or recesses, interference-fit or snap-fit, magnetic attraction, and/or the like. When coupled together (e.g., via features  1201   ac  and  1201   zc ) by inserting an end portion of housing  1201   a  into the open end of housing  1201   z  (e.g., in the direction of arrow I), body point portion  1227   p  of body stylus circuitry  1227  may puncture or rupture or otherwise pass through protective cover  1276  (if provided) and press into conductive pad  1274 , which may press conductive pad  1274  against and maintain electrical contact with end  1272  of conductive compressible component  1270 , which may compress conductive compressible component  1270  for pressing end  1271  of conductive compressible component  1270  against and maintain electrical contact with node  1299 , thereby creating and maintaining an electrical coupling of body stylus circuitry  1227  and tip stylus circuitry  1226  via conductive compressible component  1270  and conductive pad  1274 . The compressibility of conductive compressible component  1270  and/or the compressibility of conductive pad  1274  may enable any suitable mechanical tolerances between tip portion  1215  and body portion  1217  while ensuring robust electrical coupling between body stylus circuitry  1227  and tip stylus circuitry  1226  once housings  1201   a  and  1201   z  have been mechanically coupled together. Whether the coupling of housings  1201   a  and  1201   z , and thus the coupling of tip portion  1215  and body portion  1217 , is configured to be a removable coupling (e.g., a screwable/unscrewable coupling that an end user may utilize to replace one of the portions (e.g., re-use a body portion with different replaceable tip portions)) or is configured to be a fixed coupling (e.g., a glued or snap fit coupling that is configured to be done once by a manufacturer and not intended to be undone by an end user (e.g., in the direction of arrow O)), the compressibility of conductive compressible component  1270  and/or the compressibility of conductive pad  1274  may be utilized to ensure a robust electrical coupling (e.g., maintain electrical pressure) while enabling any suitable mechanical tolerances. Moreover, the compressibility of conductive compressible component  1270  and/or the compressibility of conductive pad  1274  may help prevent physical damage to portions of the accessory if dropped. For example, if the accessory were to be dropped from some height and then land on its tip, then the weight of the body portion may impart a damaging force onto the circuit board, if not for the compressibility of the conductive compressible component and/or the compressibility of the conductive pad that may be operative to reduce the force imparted by the body portion on to the circuitry (e.g., from 10,000 g&#39;s to 200 g&#39;s). If tip portion  1215  is to be removably coupled to body portion  1217  for enabling user replacement of one tip portion  1215  for another tip portion, then protective cover  1276  may be configured to be any suitable ESD protection film that may protect an ESD airgap between protective cover  1276  and conductive pad  1274  within space  1201   as  and/or that may be effectively an ESD barrier that may prevent an ESD event at back of the tip (e.g., prior to puncture of the cover by the body portion (e.g., by body point portion  1227   p  (e.g., any suitable tip or sharp or leading portion))). Some replaceable tips may be especially ESD sensitive due to potentially not having full housing protection prior to the replaceable tip being coupled to the body portion, such that the protective cover may be protecting an otherwise open and unprotected back side of the replaceable tip against ESD damage (e.g., prior to the tip being coupled to the body portion for the first time (e.g., prior to the protective cover being punctured or otherwise broken by the initial (e.g., only) coupling of the replaceable tip to the body portion) and/or while the tip is coupled to the body portion for the first time). End  1271  of conductive compressible component  1270  may be mechanically connected to node  1299  (e.g., via solder) or conductive compressible component  1270  may not be fixed to node  1299  but rather held thereagainst at least when housings  1201   a  and  1201   z  are assembled together. Similarly, end  1272  of conductive compressible component  1270  may be mechanically connected to conductive pad  1274  (e.g., via solder) or conductive compressible component  1270  may not be fixed conductive pad  1274  but rather held thereagainst at least when housings  1201   a  and  1201   z  are assembled together. 
     When tip portion  1215  is coupled to body portion  1217 , an airgap  1201   p  may exist between housing  1201   a  and housing  1201   z  (e.g., between coupling features  1201   ac  and  1201   az  and/or between any other opposing portions of housings  1201   a  and  1201   z ). During certain ESD strike events, an arc may attempt to cross airgap  1201   p . Therefore, airgap  1201   p  may be configured to be of a geometry that may prevent such behavior in order to protect the circuitry within spaces  1201   as  and  1201   zs  of housings  1201   a  and  1201   z . For example, airgap  1201   p  may be configured to be long and skinny enough (e.g., 3 centimeters long) so a voltage able to cross such a gap would need to be higher than an ESD strike is likely to produce. Alternatively, a glue may be provided to completely fill the airgap. 
     Tip component housing  1201   a  may be formed by one or more housing portions. For example, as shown, tip component housing  1201   a  may include an inner or first housing portion  1201   ai  and an outer or second housing portion  1201   ao . First housing portion  1201   ai  may be any suitable material(s), such as a high dielectric strength material, such as Nylon 11 or Polyamide 11 (e.g., a polyamide, bioplastic, and a member of the nylon family of polymers (e.g., produced by the polymerization of 11-aminoundecanoic acid (e.g., as may be produced by Arkema as RILSAN®))), where such a high dielectric strength material may be operative to reduce the electrical breakdown risk due to an ESD event. Second housing portion  1201   ao , which may be softer than first housing portion  1201   ai , may be any suitable material(s), such as polyether block amide (e.g., a thermoplastic elastomer (“TPE”) (e.g., as may be produced by Arkema as PEBAX® or by Evonik Industries as VESTAMID®)) or polyvinylidene fluoride or polyvinylidene difluoride (“PVDF”) (e.g., a highly non-reactive thermoplastic fluoropolymer (e.g., as may be produced by the polymerization of vinylidene difluoride (e.g., as may be produced by Arkema as Kynar®))). In some embodiments, tip component housing  1201   a  may be produced by molding first housing portion  1201   ai  as a first shot and then molding second housing portion  1201   ao  as a second shot about tip interface component  1221  (e.g., a metal ball) and about at least a portion of first housing portion  1201   ai . In other embodiments, tip component housing  1201   a  may not include first housing portion  1201   ai  but may be produced by molding housing portion  1201   ao  about tip interface component  1221 , where such a housing portion may take the form of the entirety of the tip component housing as a single shot housing (see, e.g., housing  1301   a  of  FIGS.  13 A and  13 B ). Body housing  1201   z  may be any suitable material(s), such as the same material(s) as housing portion  1201   ao . Body housing  1201   z  of body  1217  can be formed of one or more components operably connected together, such as a front piece and a back piece or a top clamshell and a bottom clamshell. Alternatively, body housing  1201   z  of body  1217  can be formed of a single piece (e.g., uniform body or unibody). 
     Different types of tips may be used in different embodiments. For example, as shown in  FIGS.  13 ,  13 A, and  13 B , a tip interface component  1321  may be substantially spherical or a spherical cap but may include or define a hollow feature or hollow space  1321   s . Such a hollow space  1321   s  may enable any suitable assembly tool (e.g., a pin inside an insert mold) to hold tip interface component  1321  in a particular position such that a tip component housing  1301   a  may be molded (e.g., injection molded) at least partially about tip interface component  1321  for providing any suitable tip portion  1315  (e.g., which may be the same as or similar to any one or more of tip portions  415 ,  415   a ,  415   b ,  415   c ,  415   d ,  419 ,  419   a ,  1115 , and  1215 ), where such a position during molding may ensure that a center tip  1321   c  of the spherical portion of tip interface component  1321  may be pointing towards the tip of tip portion  1315 . Any suitable accessory or stylus  1300  (e.g., which may be the same as or similar to any one or more of accessories or styli  400 ,  400   a ,  400   b ,  400   c ,  400   d ,  1100 , and  1200 ) may include tip portion  1315 . Any suitable tip stylus circuitry  1326  (e.g., which may be the same as or similar to any one or more of tip stylus circuitries  426   a ,  426   b ,  426   c ,  426   d ,  436   a ,  436   a ′,  1126 , and  1226 ) may be provided in any suitable manner on any suitable circuit board  1360  (e.g., which may be the same as or similar to any one or more of boards  1160  and  1260 ). As shown, tip component housing  1301   a  may at least partially protect one, some, or each of the components of tip component portion  1315 . For example, tip component housing  1301   a  may at least partially define a tip housing space  1301   as  within which tip interface component  1321  and/or tip stylus circuitry  1326  and/or circuit board  1360  may be at least partially positioned. Any suitable portion or node of circuitry  1326 / 1360  may be electrically coupled in any suitable manner to any suitable portion of tip interface component  1321 . In some embodiments, at least a portion of circuitry  1326  and/or at least a portion of board  1360  may extend into and be positioned within hollow space  1321   s  of tip interface component  1321 . The closer electronic components of circuitry  1326  may be to the external tip of the accessory (e.g., as may be enabled by hollow space  1321   s ), the less undesirable wobble effects may result during use of the accessory. For example, as the accessory is tilted, one or more portions of circuitry within the accessory (e.g., tip interface component  1321  and/or tip stylus circuitry  1326  and/or circuit board  1360  of accessory  1300 ) may be positioned closer to the surface of any suitable device I/O interface, which may introduce wobble by distorting the shape of the stylus electric field(s), which may distort the ability of the system to estimate the position of the tip of the accessory with respect to the surface of the device I/O interface. However, by moving more electronic components closer to center tip  1321   c  of the spherical portion of tip interface component  1321 , wobble may be reduced. 
     As shown in  FIGS.  14 ,  14 A, and  14 B , a tip interface component  1421  may be a solid sphere. Such a spherical shape may provide a symmetrical three-dimensional object such that it may be dropped into and/or held at any orientation within and/or with respect to a mold such that a second housing portion  1401   ao  of a tip component housing  1401   a  may be molded as a second shot about tip interface component  1421  and about at least a portion of a first housing portion  1401   ai  for providing any suitable tip portion  1415  (e.g., which may be the same as or similar to any one or more of tip portions  415 ,  415   a ,  415   b ,  415   c ,  415   d ,  419 ,  419   a ,  1115 ,  1215 , and  1315 ), where such a position during molding may ensure that a center tip  1421   c  of the sphere of tip interface component  1421  may be pointing towards the tip of tip portion  1415 . Any suitable accessory or stylus  1400  (e.g., which may be the same as or similar to any one or more of accessories or styli  400 ,  400   a ,  400   b ,  400   c ,  400   d ,  1100 ,  1200 , and  1300 ) may include tip portion  1415 . Any suitable tip stylus circuitry  1426  (e.g., which may be the same as or similar to any one or more of tip stylus circuitries  426   a ,  426   b ,  426   c ,  426   d ,  436   a ,  436   a ′,  1126 ,  1226 , and  1326 ) may be provided in any suitable manner on any suitable circuit board  1460  (e.g., which may be the same as or similar to any one or more of boards  1160 ,  1260 , and  1360 ). As shown, tip component housing  1401   a  may at least partially protect one, some, or each of the components of tip component portion  1415 . For example, tip component housing  1401   a  may at least partially define a tip housing space  1401   as  within which tip interface component  1421  and/or tip stylus circuitry  1426  and/or circuit board  1460  may be at least partially positioned. Any suitable portion or node of circuitry  1426 / 1460  may be electrically coupled in any suitable manner to any suitable portion of tip interface component  1421 . 
     As shown in  FIGS.  15 ,  15 A,  15 B, and  15 C , a tip interface component  1521  may be at least partially spherical (e.g., hemispherical) but may include any suitable tapered or mushroom shaped or chamfered or step portion  1521   s  extending away from a center tip  1521   c  of the spherical portion of tip interface component  1521 . Such a step portion  1521   s  may enable any suitable assembly tool (e.g., a clamp used with an insert mold) to hold tip interface component  1521  in a particular position such that a tip component housing  1501   a  may be molded (e.g., injection molded) at least partially about tip interface component  1521  for providing any suitable tip portion  1515  (e.g., which may be the same as or similar to any one or more of tip portions  415 ,  415   a ,  415   b ,  415   c ,  415   d ,  419 ,  419   a ,  1115 ,  1215 ,  1315 , and  1415 ), where such a position during molding may ensure that a center tip of the spherical portion of tip interface component  1521  may be pointing towards the tip of tip portion  1515  (e.g., such that a second housing portion  1501   ao  of tip component housing  1501   a  may be molded as a second shot about tip interface component  1521  and about at least a portion of a first housing portion  1501   ai  for providing any suitable tip portion  1515 ). Any suitable accessory or stylus  1500  (e.g., which may be the same as or similar to any one or more of accessories or styli  400 ,  400   a ,  400   b ,  400   c ,  400   d ,  1100 ,  1200 ,  1300 , and  1400 ) may include tip portion  1515 . Any suitable tip stylus circuitry  1526  (e.g., which may be the same as or similar to any one or more of tip stylus circuitries  426   a ,  426   b ,  426   c ,  426   d ,  436   a ,  436   a ′,  1126 ,  1226 ,  1326 , and  1426 ) may be provided in any suitable manner on any suitable circuit board  1560  (e.g., which may be the same as or similar to any one or more of boards  1160 ,  1260 ,  1364 , and  1460 ). As shown, tip component housing  1501   a  may at least partially protect one, some, or each of the components of tip component portion  1515 . For example, tip component housing  1501   a  may at least partially define a tip housing space  1501   as  within which tip interface component  1521  and/or tip stylus circuitry  1526  and/or circuit board  1560  may be at least partially positioned. Any suitable portion or node of circuitry  1526 / 1560  may be electrically coupled in any suitable manner to any suitable portion of tip interface component  1521 . Electrical fields (e.g., stylus electric fields detectable by an electronic device) may be different when the accessory is tilted toward the surface of any suitable device I/O interface (see, e.g., angle  118  of  FIG.  1 D  and/or angle  122  of  FIG.  1 C ) as compared to when the accessory is held straight and perpendicular to the device surface (see, e.g.,  FIG.  1 B ). For example, as the accessory is tilted, one or more portions of circuitry within the accessory (e.g., tip interface component  1521  and/or tip stylus circuitry  1526  and/or circuit board  1560  of accessory  1500 ) may be positioned closer to the surface of any suitable device I/O interface, which may introduce wobble by distorting the shape of the stylus electric field(s), which may distort the ability of the system to estimate the position of the tip of the accessory with respect to the surface of the device I/O interface. By providing step portion  1521   s  extending away from center tip  1521   c  of the spherical portion of tip interface component  1521  (e.g., by cutting away from a fully spherical tip interface component by reducing the size of the tip interface component as it extends away from center tip  1521   c ), less circuitry may be provided by tip interface component  1521 , which may reduce wobble. As shown in  FIG.  15 B , a pogo pin  1521   p  or any other suitable compressible or spring loaded or resilient feature may be provided within or at an end of tip interface component  1521 , which may provide any suitable compressible interaction between tip interface component  1521  and tip stylus circuitry  1526  and/or circuit board  1560 , which may obviate the need for any other conductive compressible component (e.g., conductive compressible component  1270  and/or conductive pad  1274  of accessory  1200 ). 
     An accessory may include one or more features to enable a grounded area to reduce wobble. For example, as shown in  FIGS.  16  and  16 A , an accessory  1600 , which may be similar to accessory  1200 , may include a tip portion  1615  with a tip interface component  1621  and a tip component housing  1601   a  and may be configured to be coupled to body stylus circuitry  1627  of a body portion. A body point portion of body stylus circuitry  1627  may puncture or rupture or otherwise pass through a protective cover  1676  (if provided) and press into a conductive pad  1674 , which may press conductive pad  1674  against and maintain electrical contact with an end of a conductive compressible component  1670 , which may compress conductive compressible component  1670  for pressing an end of conductive compressible component  1670  against and maintain electrical contact with circuitry  1626  and/or circuit board  1660  (e.g., which may be the same as or similar to any one or more of boards  1160 ,  1260 ,  1364 ,  1460 , and  1560 ) as positioned within space  1601   as  of housing  1601   a . As shown, accessory  1600  may include at least one ground trace  1662  (e.g., two ground traces  1662 ) that may extend through at least a portion of board  1660  and may be electrically coupled to body stylus circuitry  1627  (e.g., a ground rod (e.g., of a purely capacitively coupled device)) via conductive pad  1674  and/or conductive compressible component  1670 . As another example, as shown in  FIGS.  17  and  17 A , an accessory  1700 , which may be similar to accessory  1200 , may include a tip portion  1715  with a tip interface component  1721  and a tip component housing  1701   a  and may be configured to be coupled to body stylus circuitry  1727  of a body portion. A body point portion of body stylus circuitry  1727  may puncture or rupture or otherwise pass through a protective cover  1776  (if provided) and press into a conductive pad  1774 , which may press conductive pad  1774  against and maintain electrical contact with an end of a conductive compressible component  1770 , which may compress conductive compressible component  1770  for pressing an end of conductive compressible component  1770  against and maintain electrical contact with circuitry  1726  and/or circuit board  1760  (e.g., which may be the same as or similar to any one or more of boards  1160 ,  1260 ,  1364 ,  1460 ,  1560 , and  1660 ) as positioned within space  1701   as  of housing  1701   a . As shown, accessory  1700  may include at least one shield can structure  1764  (e.g., two shield can structures  1764  (e.g., one on each surface of board  1760 )) that may provide shielding to any portion(s) or all of circuitry  1726  on board  1760 . Moreover, as shown, housing  1701   a  may have a reduced structure. As another example, as shown in  FIGS.  18  and  18 A , an accessory  1800 , which may be similar to accessory  1200 , may include a tip portion  1815  with a tip interface component  1821  and a tip component housing  1801   a  and may be configured to be coupled to body stylus circuitry  1827  of a body portion. A body point portion of body stylus circuitry  1827  may puncture or rupture or otherwise pass through a protective cover  1876  (if provided) and press into a conductive pad  1874 , which may press conductive pad  1874  against and maintain electrical contact with an end of a conductive compressible component  1870 , which may compress conductive compressible component  1870  for pressing an end of conductive compressible component  1870  against and maintain electrical contact with circuitry  1826  and/or circuit board  1860  (e.g., which may be the same as or similar to any one or more of boards  1160 ,  1260 ,  1364 ,  1460 ,  1560 ,  1660 , and  1760 ) as positioned within space  1801   as  of housing  1801   a . As shown, accessory  1800  may include a shielding sleeve  1866  that may surround at least a portion of the entirety of board  1860  and extend to conductive compressible component  1870  and/or conductive pad  1874 , such that sleeve  1866  may be electrically coupled to body stylus circuitry  1827  (e.g., a ground rod (e.g., of a purely capacitively coupled device)) via conductive pad  1874  and/or conductive compressible component  1870 . Moreover, as shown, accessory  1800  may include at least one ground trace  1862  (e.g., two ground traces  1862 ) that may extend through at least a portion of board  1860  and may be electrically coupled to body stylus circuitry  1827  via conductive pad  1874  and/or conductive compressible component  1870 . Moreover, as shown, housing  1801   a  may have a reduced structure. Moreover, as shown, accessory  1800  may have a larger diameter plug. As another example, as shown in  FIGS.  19  and  19 A , an accessory  1900 , which may be similar to accessory  1200 , may include a tip portion  1915  with a tip interface component  1921  and a tip component housing  1901   a  and may be configured to be coupled to body stylus circuitry  1927  of a body portion. A body point portion of body stylus circuitry  1927  may puncture or rupture or otherwise pass through a protective cover  1976  (if provided) and press into a conductive pad  1974 , which may press conductive pad  1974  against and maintain electrical contact with an end of a conductive compressible component  1970 , which may compress conductive compressible component  1970  for pressing an end of conductive compressible component  1970  against and maintain electrical contact with circuitry  1926  and/or circuit board  1960  (e.g., which may be the same as or similar to any one or more of boards  1160 ,  1260 ,  1364 ,  1460 ,  1560 ,  1660 ,  1760 , and  1860 ) as positioned within space  1901   as  of housing  1901   a . As shown, accessory  1900  may include a shielding sleeve  1966  that may surround at least a portion of the entirety of board  1960  and extend to conductive compressible component  1970  and/or conductive pad  1974 , such that sleeve  1966  may be electrically coupled to body stylus circuitry  1927  (e.g., a ground rod (e.g., of a purely capacitively coupled device)) via conductive pad  1974  and/or conductive compressible component  1970 . Moreover, as shown, housing  1901   a  may have a reduced structure. Moreover, as shown, accessory  1900  may have a larger diameter plug. 
     Moreover, the processes described with respect to  FIGS.  1 - 19 A  (e.g., any control applications and/or algorithms), as well as any other aspects of the disclosure, may each be implemented by software, but may also be implemented in hardware, firmware, or any combination of software, hardware, and firmware. They each may also be embodied as computer-readable code recorded on a computer-readable medium. The computer-readable medium may be any data storage device that can store data or instructions which can thereafter be read by a computer system. Examples of the computer-readable medium may include, but are not limited to, read-only memory, random-access memory, flash memory, CD-ROMs, DVDs, magnetic tape, and optical data storage devices (e.g., memory  104  of  FIG.  1   ). The computer-readable medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. For example, the computer-readable medium may be communicated from one electronic device to another electronic device using any suitable communications protocol. The computer-readable medium may embody computer-readable code, instructions, data structures, program modules, or other data in a modulated data signal, such as a carrier wave or other transport mechanism, and may include any information delivery media. A modulated data signal may be a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. 
     As mentioned, electronic device  100  may drive a display (e.g., display  112   a ) with graphical data to display a graphical user interface (“GUI”). The GUI may be configured to receive touch input via input component(s)  110   a  and/or  110   b . Embodied as a touch screen (e.g., with display  112   a  as I/O component  111   a ), I/O component  111   a  may display the GUI. Alternatively, the GUI may be displayed on a display (e.g., display  112   a ) separate from touch input component  110 . The GUI may include graphical elements displayed at particular locations within the interface. Graphical elements may include, but are not limited to, a variety of displayed virtual input devices, including virtual scroll wheels, a virtual keyboard, virtual knobs, virtual buttons, any virtual UI, and the like. A user may perform gestures (e.g., user fingers and/or with stylus  400 ) at one or more particular locations on input component(s)  110   a  and/or  110   b , which may be associated with the graphical elements of the GUI. In other embodiments, the user may perform gestures at one or more locations that are independent of the locations of graphical elements of the GUI. Gestures performed on input component(s)  110   a  and/or  110   b  may directly or indirectly manipulate, control, modify, move, actuate, initiate, or generally affect graphical elements, such as cursors, icons, media files, lists, text, all or portions of images, or the like within the GUI. For instance, in the case of a touch screen, a user may directly interact with a graphical element by performing a gesture over the graphical element on the touch screen. Alternatively, a touch pad may generally provide indirect interaction. Gestures may also affect non-displayed GUI elements (e.g., causing user interfaces to appear) or may affect other actions of device  100  (e.g., affect a state or mode of a GUI, application, or operating system). Gestures may or may not be performed on input component(s)  110   a  and/or  110   b  in conjunction with a displayed cursor. For instance, in the case in which gestures are performed on a touchpad, a cursor (or pointer) may be displayed on a display screen or touch screen and the cursor may be controlled via touch input on the touchpad to interact with graphical objects on the display screen. In other embodiments, in which gestures are performed directly on a touch screen, a user may interact directly with objects on the touch screen, with or without a cursor or pointer being displayed on the touch screen. 
     Feedback may be provided to the user via bus  114  in response to or based on the touch or near touches on a touch input component  110 . Feedback may be transmitted optically, mechanically, electrically, via olfactory, acoustically, or the like or any combination thereof and in a variable or non-variable manner. 
     Circuitry may be disposed on a printed circuit board (“PCB”) or a flexible printed circuit (“FPC”) (e.g., circuitry  1126  on board  1160 , circuitry  1226  on board  1260 , circuitry  1326  on board  1360 , circuitry  1426  on board  1460 , circuitry  1526  on board  1560 , circuitry  1626  on board  1660 , circuitry  1726  on board  1760 , circuitry  1826  on board  1860 , circuitry  1926  on board  1960 , etc.). In some embodiments, the circuitry may include discrete circuit elements coupled together (e.g., coupled together with solder) without a PCB or FPC. Although this disclosure describes and illustrates particular circuitry that includes particular circuit elements coupled in particular configurations, this disclosure contemplates any suitable circuitry and/or circuits that include any suitable circuit elements coupled in any suitable configurations. 
     Many alterations and modifications of the preferred embodiments will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that the particular embodiments shown and described by way of illustration are in no way intended to be considered limiting. Thus, references to the details of the described embodiments are not intended to limit their scope.