PATENT DOCUMENT

Publication Number: US-10474277-B2
Application Number: US-201615169679-A
Country: US
Kind Code: B2

Title: Position-based stylus communication

Abstract:
Position-based sensing methods and systems can be used to transmit data from an input device to a touch-sensitive device. For example, the touch sensing system may perform one or more coarse input device sub-scans to determine a coarse location of the input device. The coarse location can be used to select one or more touch sensors (or sensor channels) to sample for decoding data encoded in the stimulation signals from the input device. During one or more fine input device sub-scans, the touch sensing system can determine a fine location of the input device and decode the data from the input device sampled from the selected touch sensors (or sensor channels).

Claims:
What is claimed is: 
     
       1. A touch-sensitive device, comprising:
 a plurality of touch sensors; 
 a first multiplexer having one or more inputs, the inputs of the first multiplexer coupled to the plurality of touch sensors; 
 a plurality of sense channels configured to receive signals from an input device at the plurality of touch sensors via one or more outputs of the first multiplexer; 
 a plurality of digital signal processors coupled to outputs of the plurality of sense channels, wherein the plurality of digital signal processors includes a plurality of first demodulators configured to demodulate the received signals, wherein outputs of the plurality of digital signal processors are indicative of which locations on the touch-sensitive device the input device is touching; 
 a position estimation processor coupled to the outputs of the plurality of digital signal processors, the position estimation processor configured to estimate a location of the input device based on a first plurality of received signals from the plurality of sense channels processed by the plurality of digital signal processors, and configured to select a subset of the plurality of sense channels coupled to one or more of the plurality of touch sensors proximate to the input device based on the estimated location of the input device; 
 a plurality of correlators couplable to the outputs of the selected subset of the plurality of sense channels, wherein the plurality of correlators each comprise a plurality of second demodulators, the second demodulators configured to demodulate a second plurality of received signals from the selected subset of the plurality of sense channels, the plurality of correlators configured to determine frequency content of the demodulated second plurality of received signals to obtain encoded data from the second plurality of received signals, wherein a number of the plurality of correlators is less than a number of sense channels included in the touch-sensitive device; and 
 a plurality of second multiplexers, each second multiplexer having an output connected to one of the plurality of correlators and configured to couple one sense channel of the selected subset of sense channels to one of the plurality of correlators to simultaneously couple the selected subset of sense channels to the plurality of correlators. 
 
     
     
       2. The touch-sensitive device of  claim 1 , wherein a correlator of the plurality of correlators further comprises an adder coupled to a plurality of outputs of the second demodulators, and the correlator is configured to determine the frequency content of an output of the adder. 
     
     
       3. The touch-sensitive device of  claim 1 , wherein the first plurality of received signals are received while the touch-sensitive device is configured in a first configuration, the first configuration including coupling two or more touch sensors of the plurality of touch sensors to each sense channel. 
     
     
       4. The touch-sensitive device of  claim 1 , wherein the second plurality of received signals are received while the touch-sensitive device is configured in a second configuration, the second configuration including coupling one touch sensor of the plurality of touch sensors to each sense channel. 
     
     
       5. The touch-sensitive device of  claim 1 , further comprising:
 a wireless transceiver configured to communicate with a wireless transceiver of the input device, wherein the encoded data comprises pairing information for establishing a connection between the wireless transceiver and the wireless transceiver of the input device. 
 
     
     
       6. The touch-sensitive device of  claim 1 , wherein:
 the plurality of touch sensors comprise row sensors and column sensors, the row sensors orthogonal to the column sensors, 
 during a first time period, a plurality of row sensors are coupled, via the selected subset of sense channels, to the plurality of correlators to demodulate first data, and 
 during a second time period after the first time period, a plurality of column sensors are coupled, via the selected subset of sense channels, to the plurality of correlators to demodulate second data different from the first data. 
 
     
     
       7. A method implemented by a touch-sensitive device for decoding data transmitted by an input device, the method comprising:
 sensing, at a plurality of touch sensors, signals from the input device, wherein the touch sensors are coupled to one or more inputs of a first multiplexer; 
 receiving, at a plurality of sense channels, a first plurality of signals from the input device via one or more outputs of the first multiplexer; 
 demodulating, with a plurality of first demodulators included in a plurality of digital signal processors, the received first plurality of signals, wherein outputs of the plurality of digital signal processors are indicative of which locations on the touch-sensitive device the input device is touching; 
 estimating, with a position estimation processor coupled to the outputs of the plurality of digital signal processors, a location of the input device relative to a touch sensitive surface based on the demodulated signals; 
 selecting, with the position estimation processor, a subset of the plurality of sense channels coupled to the touch sensitive surface based on the estimated location of the input device, wherein the selected subset of the plurality of sense channels are coupled to one or more of the plurality of touch sensors of the touch sensitive surface proximate to the input device; 
 simultaneously coupling, via a plurality of second multiplexers, each of the selected subset of the plurality of sense channels to a correlator of a plurality of correlators, each correlator of the plurality of correlators comprising a plurality of second demodulators, wherein a number of the plurality of correlators is less than a number of the plurality of sense channels, wherein each second multiplexer has an output connected to one of the plurality of correlators; and 
 decoding, with the plurality of correlators, encoded data from a second plurality of signals received at the subset of the plurality of sense channels and demodulated by the plurality of second demodulators by determining frequency content of the demodulated second plurality of received signals. 
 
     
     
       8. The method of  claim 7 , further comprising:
 receiving the first plurality of received signals during a first operation, the first operation comprising coupling two or more touch sensors of the touch sensitive surface to each sense channel. 
 
     
     
       9. The method of  claim 7 , further comprising:
 receiving the second plurality of received signals during a second operation, the second operation comprising coupling one touch sensor of the touch sensitive surface to each of the subset of the plurality of sense channels. 
 
     
     
       10. The method of  claim 7 , further comprising:
 establishing a wireless communication channel between a wireless transceiver and a wireless transceiver included in the input device based on pairing information encoded in the encoded data from the second plurality of signals. 
 
     
     
       11. The method of  claim 7  wherein:
 the plurality of touch sensors comprise row sensors and column sensors, the row sensors orthogonal to the column sensors, 
 during a first time period, a plurality of row sensors are coupled, via the selected subset of sense channels, to the plurality of correlators to demodulate first data, and 
 during a second time period after the first time period, a plurality of column sensors are coupled, via the selected subset of sense channels, to the plurality of correlators to demodulate second data different from the first data. 
 
     
     
       12. A non-transitory computer readable storage medium storing one or more programs, the one or more programs comprising instructions, which when executed by an electronic device including one or more processors, causes the electronic device to perform a method comprising:
 sensing, at a plurality of touch sensors, signals from an input device, wherein the touch sensors are coupled to one or more inputs of a first multiplexer; 
 receiving, at a plurality of sense channels, a first plurality of signals from the input device via one or more outputs of the first multiplexer; 
 demodulating, with a plurality of first demodulators included in a plurality of digital signal processors, the received first plurality of signals, wherein outputs of the plurality of digital signal processors are indicative of which locations on the electronic device the input device is touching; 
 estimating, with a position estimation processor coupled to the outputs of the plurality of digital signal processors, a location of the input device relative to a touch sensitive surface based on the demodulated signals; 
 selecting, with the position estimation processor, a subset of the plurality of sense channels coupled to the touch sensitive surface based on the estimated location of the input device, wherein the selected subset of the plurality of sense channels are coupled to one or more of the plurality of touch sensors of the touch sensitive surface proximate to the input device; 
 simultaneously coupling, via a plurality of second multiplexers, each of the selected subset of the plurality of sense channels to a correlator of a plurality of correlators, each correlator of the plurality of correlators comprising a plurality of second demodulators, wherein a number of the plurality of correlators is less than a number of the plurality of sense channels, wherein each second multiplexer has an output connected to one of the plurality of correlators; and 
 decoding, with the plurality of correlators, encoded data from a second plurality of signals received at the subset of the plurality of sense channels and demodulated by the plurality of second demodulators by determining frequency content of the demodulated second plurality of received signals. 
 
     
     
       13. The non-transitory computer readable storage medium of  claim 12 , wherein the method further comprises:
 receiving the first plurality of received signals during a first operation, the first operation comprising coupling two or more touch sensors of the touch sensitive surface to each sense channel. 
 
     
     
       14. The non-transitory computer readable storage medium of  claim 12 , wherein the method further comprises:
 receiving the second plurality of received signals during a second operation, the second operation comprising coupling one touch sensor of the touch sensitive surface to each of the subset of the plurality of sense channels. 
 
     
     
       15. The non-transitory computer readable storage medium of  claim 12 , wherein the method further comprises:
 establishing a wireless communication channel between a wireless transceiver and a wireless transceiver included in the input device based on pairing information encoded in the encoded data from the second plurality of signals. 
 
     
     
       16. The non-transitory computer readable storage medium of  claim 12 , wherein:
 the plurality of touch sensors comprise row sensors and column sensors, the row sensors orthogonal to the column sensors, 
 during a first time period, a plurality of row sensors are coupled, via the selected subset of sense channels, to the plurality of correlators to demodulate first data, and 
 during a second time period after the first time period, a plurality of column sensors are coupled, via the selected subset of sense channels, to the plurality of correlators to demodulate second data different from the first data. 
 
     
     
       17. An apparatus comprising:
 a plurality of touch sensors; 
 a first multiplexer having one or more inputs, the inputs of the first multiplexer coupled to the plurality of touch sensors; 
 a plurality of sense channels configured to receive signals from an input device at the plurality of touch sensors via one or more outputs of the first multiplexer; 
 a plurality of digital signal processors coupled to outputs of the plurality of sense channels, wherein the plurality of digital signal processors includes a plurality of first demodulators configured to demodulate the received signals, wherein outputs of the plurality of digital signal processors are indicative of which locations on the apparatus the input device is touching; 
 a position estimation processor coupled to the outputs of the plurality of digital signal processors, the position estimation processor configured to estimate a location of the input device based on a first plurality of signals received from the plurality of sense channels selected by the first multiplexer and processed by the plurality of digital signal processors, the position estimation processor configured to select a subset of the plurality of sense channels coupled to one or more of the plurality of touch sensors proximate to the input device based on the estimated location of the input device; and 
 a plurality of correlators couplable to the selected subset of the plurality of sense channels, wherein each of the plurality of correlators comprise a plurality of second demodulators, the second demodulators configured to demodulate a second plurality of received signals from the selected subset of the plurality of sense channels, the plurality of correlators configured to determine frequency content of the demodulated second plurality of received signals to obtain encoded data from the second plurality of received signals from the selected subset of the plurality of sense channels, wherein a number of the plurality of correlators is less than a number of sense channels included in the apparatus; and 
 a plurality of second multiplexers, each second multiplexer having an output connected to one of the plurality of correlators and configured to couple one sense channel of the selected subset of sense channels to one of the plurality of correlators to simultaneously couple the selected subset of sense channels to the plurality of correlators. 
 
     
     
       18. The apparatus of  claim 17 , wherein a correlator of the plurality of correlators further comprises an adder coupled to a plurality of outputs of the second demodulators. 
     
     
       19. The apparatus of  claim 17 , wherein the first plurality of signals are received while two or more touch sensors of the plurality of touch sensors are coupled to each sense channel. 
     
     
       20. The apparatus of  claim 17 , wherein the second plurality of signals are received while one touch sensor of the plurality of touch sensors is coupled to each sense channel. 
     
     
       21. The apparatus of  claim 17 , further comprising:
 a wireless transceiver configured to communicate with a wireless transceiver of the input device, wherein the frequency content of the demodulated signals comprises pairing information for establishing a connection between the wireless transceiver and the wireless transceiver of the input device. 
 
     
     
       22. The apparatus of  claim 17 , wherein:
 the plurality of touch sensors comprise row sensors and column sensors, the row sensors orthogonal to the column sensors, 
 during a first time period, a plurality of row sensors are coupled, via the selected subset of sense channels, to the plurality of correlators to demodulate first data, and 
 
       during a second time period after the first time period, a plurality of column sensors are coupled, via the selected subset of sense channels, to the plurality of correlators to demodulate second data different from the first data.

Description:
FIELD OF DISCLOSURE 
     This relates generally to communication between input devices and computing devices, and more specifically, to position-based communication between an input device and computing device. 
     BACKGROUND OF DISCLOSURE 
     Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch panels, touch screens and the like. Touch-sensitive devices, and touch screens in particular, are quite popular because of their ease and versatility of operation as well as their affordable prices. A touch-sensitive device can include a touch panel, which can be a clear panel with a touch-sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. The touch-sensitive device can allow a user to perform various functions by touching or hovering over the touch panel using a finger, stylus or other object at a location often dictated by a user interface (UI) being displayed by the display device. In general, the touch-sensitive device can recognize a touch or hover event and the position of the event on the touch panel, and the computing system can then interpret the event in accordance with the display appearing at the time of the event, and thereafter can perform one or more actions based on the event. 
     Styli have become popular input devices for touch-sensitive devices. In particular, use of an active stylus capable of generating stylus stimulation signals that can be sensed by the touch-sensitive device can improve the precision and control of the stylus. In some instances it may be desirable for input devices, such as styli, to be able to transfer data, in addition to a stimulation signal used to identify touch location, to the touch screen. For example, data from the input devices (such as force, orientation, tilt, or the like) may be communicated to the touch screen, which may use that data to change an output of the display or perform some other operation. 
     SUMMARY OF DISCLOSURE 
     In some examples herein, an input device and methods for transmitting data from the input device through a capacitive coupling or touch screen interface are disclosed. For example, an active stylus may generate stimulation signals that are received by a plurality of touch sensors of a touch sensitive display to detect the presence and location of the stylus. In some examples, the stylus stimulation signals can also include encoded data. The touch sensing system may select one or more touch sensors (or sense channels) proximate to the stylus to sample, receive, and decode the encoded data. In some examples, selecting the one or more touch sensors (or sense channels) to receive encoded data can reduce hardware requirements because data receiver channels are not required for each touch sensor (or touch sensor channel). To decode frequency-encoded stylus data, the touch sensing system can determine a frequency spectrum of the sampled data. Upon determining which frequency/frequencies are transmitted by the stylus, the data can be decoded. 
     In some examples, the touch sensing system may perform one or more coarse input device sub-scans to determine a coarse location of the input device. The coarse location can be used to select one or more touch sensors (or sensor channels) to sample for decoding data from the input device. During one or more fine input device sub-scans, the touch sensing system can determine a fine location of the input device and decode the data from the input device sampled from the selected touch sensors (or sensor channels). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1D  illustrate examples of systems with touch screens that can accept input from an active stylus according to examples of the disclosure. 
         FIG. 2  illustrates a block diagram of an example computing system that can receive input from an active stylus according to examples of the disclosure. 
         FIG. 3  illustrates an example touch screen including touch sensing circuitry configured as drive and sense regions or lines according to examples of the disclosure. 
         FIG. 4  illustrates an example touch screen including touch sensing circuitry configured as pixelated electrodes according to examples of the disclosure. 
         FIG. 5  illustrates an example active stylus according to examples of the disclosure. 
         FIG. 6  illustrates an example touch sensor panel configuration operable with the touch ASIC of  FIG. 2  to perform a stylus scan according to examples of the disclosure. 
         FIG. 7  illustrates an example touch sensor panel configuration operable with the touch ASIC of  FIG. 2  to perform a stylus scan according to examples of the disclosure. 
         FIG. 8  illustrates an example pairing operation between a stylus and a host device via a wired connection according to examples of the disclosure. 
         FIGS. 9A-9C  illustrate exemplary coarse stylus sub-scans according to examples of the disclosure. 
         FIG. 10  illustrates an example timing diagram for stylus activity and touch sensor panel activity, according to examples of the disclosure. 
         FIGS. 11A-11B  illustrate exemplary stylus signal analysis hardware according to examples of the disclosure. 
         FIG. 12  illustrates an example block diagram of a touch sensing system including position-based data decoding according to examples of the disclosure. 
         FIGS. 13A-13B  illustrate exemplary stylus data processing hardware according to examples of the disclosure. 
         FIG. 14  illustrates an example process for decoding data included in a stylus stimulation signal according to examples of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of examples, reference is made to the accompanying drawings in which it is shown by way of illustration specific examples that can be practiced. It is to be understood that other examples can be used and structural changes can be made without departing from the scope of the various examples. 
     In some examples herein, an input device and methods for transmitting data from the input device through a capacitive coupling or touch screen interface are disclosed. For example, an active stylus may generate stimulation signals that are received by a plurality of touch sensors of a touch sensitive display to detect the presence and location of the stylus. In some examples, the stylus stimulation signals can also include encoded data. The touch sensing system may select one or more touch sensors (or sense channels) proximate to the stylus to sample to receive and decode the encoded data. In some examples, selecting the one or more touch sensors (or sense channels) to receive encoded data can reduce hardware requirements because data receiver channels are not required for each touch sensor (or touch sensor channel). To decode frequency-encoded stylus data, the touch sensing system can determine a frequency spectrum of the sampled data. Upon determining which frequency/frequencies are transmitted by the stylus, the data can be decoded. 
     In some examples, the touch sensing system may perform one or more coarse input device sub-scans to determine a coarse location of the input device. The coarse location can be used to select one or more touch sensors (or sensor channels) to sample for decoding data from the input device. During one or more fine input device sub-scans, the touch sensing system can determine a fine location of the input device and decode the data from the input device sampled from the selected touch sensors (or sensor channels). 
       FIGS. 1A-1D  illustrate examples of systems with touch screens that can accept input from an active stylus according to examples of the disclosure.  FIG. 1A  illustrates an exemplary mobile telephone  136  that includes a touch screen  124  that can accept input from an active stylus according to examples of the disclosure.  FIG. 1B  illustrates an example digital media player  140  that includes a touch screen  126  that can accept input from an active stylus according to examples of the disclosure.  FIG. 1C  illustrates an example personal computer  144  that includes a touch screen  128  that can accept input from an active stylus according to examples of the disclosure. In some examples, a personal computer  144  can include a trackpad that can accept input from an active stylus according to examples of the disclosure. Although generally described herein with regard to touch screens, active stylus input can be received by touch-sensitive surfaces without a display.  FIG. 1D  illustrates an example tablet computing device  148  that includes a touch screen  130  that can accept input from an active stylus according to examples of the disclosure. Other devices, including wearable devices, can accept input from an active stylus according to examples of the disclosure. 
     Touch screens  124 ,  126 ,  128  and  130  can be based on, for example, self-capacitance or mutual capacitance sensing technology, or another touch sensing technology. For example, in a self-capacitance based touch system, an individual electrode with a self-capacitance to ground can be used to form a touch pixel (touch node) for detecting touch. As an object approaches the touch pixel, an additional capacitance to ground can be formed between the object and the touch pixel. The additional capacitance to ground can result in a net increase in the self-capacitance seen by the touch pixel. This increase in self-capacitance can be detected and measured by a touch sensing system to determine the positions of multiple objects when they touch the touch screen. 
     A mutual capacitance based touch system can include, for example, drive regions and sense regions, such as drive lines and sense lines. For example, drive lines can be formed in rows while sense lines can be formed in columns (i.e., orthogonal). Touch pixels (touch nodes) can be formed at the intersections or adjacencies (in single layer configurations) of the rows and columns. During operation, the rows can be stimulated with an alternating current (AC) waveform and a mutual capacitance can be formed between the row and the column of the touch pixel. As an object approaches the touch pixel, some of the charge being coupled between the row and column of the touch pixel can instead be coupled onto the object. This reduction in charge coupling across the touch pixel can result in a net decrease in the mutual capacitance between the row and the column and a reduction in the AC waveform being coupled across the touch pixel. This reduction in the charge-coupled AC waveform can be detected and measured by the touch sensing system to determine the positions of multiple objects when they touch the touch screen. In some examples, a touch screen can be multi-touch, single touch, projection scan, full-imaging multi-touch, or any capacitive touch. 
     In some examples, one or more touch sensors can detect signals from a powered stylus via mutual capacitance. Rather than generating a stimulation signal, the touch sensors can be used to receive coupled charge indicative of the stylus&#39; stimulation signals. As the stylus approaches a touch sensor, charge coupling can occur between a conductive tip of the stylus (which can be driven by the stylus stimulation signal) and the touch sensor. This charge coupling can be received as an AC waveform indicative of stylus presence. In some examples, stylus stimulation signals can be sampled, analyzed, and decoded to receive data encoded in the stylus signal. 
       FIG. 2  illustrates a block diagram of an example computing system  200  that can receive input from an active stylus according to examples of the disclosure. Computing system  200  could be included in, for example, mobile telephone  136 , digital media player  140 , personal computer  144 , tablet computing device  148 , wearable device, or any mobile or non-mobile computing device that includes a touch screen. Computing system  200  can include an integrated touch screen  220  to display images and to detect touch and/or proximity (e.g., hover) events from an object (e.g., finger  203  or active or passive stylus  205 ) at or proximate to the surface of the touch screen  220 . Computing system  200  can also include an application specific integrated circuit (“ASIC”) illustrated as touch ASIC  201  to perform touch and/or stylus sensing operations. Touch ASIC  201  can include one or more touch processors  202 , peripherals  204 , and touch controller  206 . Touch ASIC  201  can be coupled to touch sensing circuitry of touch screen  220  to perform touch and/or stylus sensing operations (described in more detail below). Peripherals  204  can include, but are not limited to, random access memory (RAM) or other types of memory or storage, watchdog timers and the like. Touch controller  206  can include, but is not limited to, one or more sense channels in receive circuitry  208 , panel scan engine  210  (which can include channel scan logic) and transmit circuitry  214  (which can include analog or digital driver logic). In some examples, the transmit circuitry  214  and receive circuitry  208  can be reconfigurable by the panel scan engine  210  based the scan event to be executed (e.g., mutual capacitance row-column scan, mutual capacitance row-row scan, mutual capacitance column-column scan, row self-capacitance scan, column self-capacitance scan, pixelated sensor array scan, stylus data scan, stylus location scan, etc.). Panel scan engine  210  can access RAM  212 , autonomously read data from the sense channels and provide control for the sense channels. The touch controller  206  can also include a scan plan (e.g., stored in RAM  212 ) which can define a sequence of scan events to be performed at the touch screen. The scan plan can include information necessary for configuring or reconfiguring the transmit circuitry and receive circuitry for the specific scan event to be performed. Results (e.g., touch/stylus signals or touch/stylus data) from the various scans can also be stored in RAM  212 . In addition, panel scan engine  210  can provide control for transmit circuitry  214  to generate stimulation signals at various frequencies and/or phases that can be selectively applied to drive regions of the touch sensing circuitry of touch screen  220 . Although illustrated in  FIG. 2  as a single ASIC, the various components and/or functionality of the touch ASIC  201  can be implemented with multiple circuits, elements, chips, and/or discrete components. 
     Computing system  200  can also include an application specific integrated circuit illustrated as display ASIC  216  to perform display operations. Display ASIC  216  can include hardware to process one or more still images and/or one or more video sequences for display on touch screen  220 . Display ASIC  216  can be configured to generate read memory operations to read the data representing the frame/video sequence from a memory (not shown) through a memory controller (not shown), for example. Display ASIC  216  can be configured to perform various processing on the image data (e.g., still images, video sequences, etc.). In some examples, display ASIC  216  can be configured to scale still images and to dither, scale and/or perform color space conversion on the frames of a video sequence. Display ASIC  216  can be configured to blend the still image frames and the video sequence frames to produce output frames for display. Display ASIC  216  can also be more generally referred to as a display controller, display pipe, display control unit, or display pipeline. The display control unit can be generally any hardware and/or firmware configured to prepare a frame for display from one or more sources (e.g., still images and/or video sequences). More particularly, display ASIC  216  can be configured to retrieve source frames from one or more source buffers stored in memory, composite frames from the source buffers, and display the resulting frames on touch screen  220 . Accordingly, display ASIC  216  can be configured to read one or more source buffers and composite the image data to generate the output frame. 
     Display ASIC  216  can provide various control and data signals to the display, including timing signals (e.g., one or more clock signals) and/or vertical blanking period and horizontal blanking interval controls. The timing signals can include a pixel clock that can indicate transmission of a pixel. The data signals can include color signals (e.g., red, green, blue). The display ASIC  216  can control the touch screen  220  in real-time, providing the data indicating the pixels to be displayed as the touch screen is displaying the image indicated by the frame. The interface to such a touch screen  220  can be, for example, a video graphics array (VGA) interface, a high definition multimedia interface (HDMI), a digital video interface (DVI), a LCD interface, a plasma interface, or any other suitable interface. 
     In some examples, a handoff module  218  can also be included in computing system  200 . Handoff module  218  can be coupled to the touch ASIC  201 , display ASIC  216 , and touch screen  220 , and can be configured to interface the touch ASIC  201  and display ASIC  216  with touch screen  220 . The handoff module  218  can appropriately operate the touch screen  220  according to the scanning/sensing and display instructions from the touch ASIC  201  and the display ASIC  216 . In other examples, the display ASIC  216  can be coupled to display circuitry of touch screen  220  and touch ASIC  201  can be coupled to touch sensing circuitry of touch screen  220  without handoff module  218 . 
     Touch screen  220  can use liquid crystal display (LCD) technology, light emitting polymer display (LPD) technology, organic LED (OLED) technology, or organic electro luminescence (OEL) technology, although other display technologies can be used in other examples. In some examples, the touch sensing circuitry and display circuitry of touch screen  220  can be stacked on top of one another. For example, a touch sensor panel can cover some or all of a surface of the display (e.g., fabricated one on top of the next in a single stack-up or formed from adhering together a touch sensor panel stack-up with a display stack-up). In other examples, the touch sensing circuitry and display circuitry of touch screen  220  can be partially or wholly integrated with one another. The integration can be structural and/or functional. For example, some or all of the touch sensing circuitry can be structurally in between the substrate layers of the display (e.g., between two substrates of a display pixel cell). Portions of the touch sensing circuitry formed outside of the display pixel cell can be referred to as “on-cell” portions or layers, whereas portions of the touch sensing circuitry formed inside of the display pixel cell can be referred to as “in cell” portions or layers. Additionally, some electronic components can be shared, and used at times as touch sensing circuitry and at other times as display circuitry. For example, in some examples, common electrodes can be used for display functions during active display refresh and can be used to perform touch sensing functions during touch sensing periods. A touch screen stack-up sharing components between sensing functions and display functions can be referred to as an in-cell touch screen. 
     Computing system  200  can also include a host processor  228  coupled to the touch ASIC  201 , and can receive outputs from touch ASIC  201  (e.g., from touch processor  202  via a communication bus, such as an serial peripheral interface (SPI) bus, for example) and perform actions based on the outputs. Host processor  228  can also be connected to program storage  232  and display ASIC  216 . Host processor  228  can, for example, communicate with display ASIC  216  to generate an image on touch screen  220 , such as an image of a user interface (UI), and can use touch ASIC  201  (including touch processor  202  and touch controller  206 ) to detect a touch on or near touch screen  220 , such as a touch input to the displayed UI. The touch input can be used by computer programs stored in program storage  232  to perform actions that can include, but are not limited to, moving an object such as a cursor or pointer, scrolling or panning, adjusting control settings, opening a file or a document, viewing a menu, making a selection, executing instructions, operating a peripheral device connected to the host device, answering a telephone call, placing a telephone call, terminating a telephone call, changing the volume or audio settings, storing information related to telephone communications such as addresses, frequently dialed numbers, received calls, missed calls, logging onto a computer or a computer network, permitting authorized individuals access to restricted areas of the computer or computer network, loading a user profile associated with a user&#39;s preferred arrangement of the computer desktop, permitting access to web content, launching a particular program, encrypting or decoding a message, and/or the like. As described herein, host processor  228  can also perform additional functions that may not be related to touch processing. 
     Computing system  200  can include one or more processors, which can execute software or firmware implementing various functions. Specifically, for integrated touch screens which share components between touch and/or stylus sensing and display functions, the touch ASIC and display ASIC can be synchronized so as to properly share the circuitry of the touch sensor panel. The one or more processors can include one or more of the one or more touch processors  202 , a processor in display ASIC  216 , and/or host processor  228 . In some examples, the display ASIC  216  and host processor  228  can be integrated into a single ASIC, though in other examples, the host processor  228  and display ASIC  216  can be separate circuits coupled together. In some examples, host processor  228  can act as a master circuit and can generate synchronization signals that can be used by one or more of the display ASIC  216 , touch ASIC  201  and handoff module  218  to properly perform sensing and display functions for an in-cell touch screen. The synchronization signals can be communicated directly from the host processor  228  to one or more of the display ASIC  216 , touch ASIC  201  and handoff module  218 . Alternatively, the synchronization signals can be communicated indirectly (e.g., touch ASIC  201  or handoff module  218  can receive the synchronization signals via the display ASIC  216 ). 
     Computing system  200  can also include a wireless module (not shown). The wireless module can implement a wireless communication standard such as a WIFI®, BLUETOOTH™ or the like. The wireless module can be coupled to the touch ASIC  201  and/or host processor  228 . The touch ASIC  201  and/or host processor  228  can, for example, transmit scan plan information, timing information, and/or frequency information to the wireless module to enable the wireless module to transmit the information to an active stylus, for example (i.e., a stylus capable generating and injecting a stimulation signal into a touch sensor panel). For example, the computing system  200  can transmit frequency information indicative of one or more low noise frequencies that the stylus can use to generate a stimulation signals. Additionally or alternatively, timing information can be used to synchronize the stylus  205  with the computing system  200 , and the scan plan information can be used to indicate to the stylus  205  when the computing system  200  performs a stylus scan and expects stylus stimulation signals (e.g., to save power by generating a stimulus only during a stylus scan period). In some examples, the wireless module can also receive information from peripheral devices, such as an active stylus  205 , which can be transmitted to the touch ASIC  201  and/or host processor  228 . In other examples, the wireless communication functionality can be incorporated in other components of computing system  200 , rather than in a dedicated chip. 
     Note that one or more of the functions described herein can be performed by firmware stored in memory and executed by the touch processor in touch ASIC  201 , or stored in program storage and executed by host processor  228 . The firmware can also be stored and/or transported within any non-transitory computer-readable storage medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “non-transitory computer-readable storage medium” can be any medium (excluding a signal) that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device. The non-transitory computer readable medium storage can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device, a portable computer diskette (magnetic), a random access memory (RAM) (magnetic), a read-only memory (ROM) (magnetic), an erasable programmable read-only memory (EPROM) (magnetic), a portable optical disc such a CD, CD-R, CD-RW, DVD, DVD-R, or DVD-RW, or flash memory such as compact flash cards, secured digital cards, USB memory devices, memory sticks, and the like. 
     The firmware can also be propagated within any transport medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “transport medium” can be any medium that can communicate, propagate or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The transport readable medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic or infrared wired or wireless propagation medium. 
     It is to be understood that the computing system  200  is not limited to the components and configuration of  FIG. 2 , but can include other or additional components in multiple configurations according to various examples. Additionally, the components of computing system  200  can be included within a single device, or can be distributed between multiple devices. 
     As discussed above, the touch screen  220  can include touch sensing circuitry.  FIG. 3  illustrates an example touch screen including touch sensing circuitry configured as drive and sense regions or lines according to examples of the disclosure. Touch screen  320  can include touch sensing circuitry that can include a capacitive sensing medium having a plurality of drive lines  322  and a plurality of sense lines  323 . It should be noted that the term “lines” is sometimes used herein to mean simply conductive pathways, as one skilled in the art will readily understand, and is not limited to elements that are strictly linear, but includes pathways that change direction, and includes pathways of different size, shape, materials, etc. Additionally, the drive lines  322  and sense lines  323  can be formed from smaller electrodes coupled together to form drive lines and sense lines. Drive lines  322  can be driven by stimulation signals from the transmit circuitry  214  through a drive interface  324 , and resulting sense signals generated in sense lines  323  can be transmitted through a sense interface  325  to sense channels of receive circuitry  208  (also referred to as an event detection and demodulation circuit) in touch controller  206 . In this way, drive lines and sense lines can be part of the touch sensing circuitry that can interact to form capacitive sensing nodes, which can be thought of as touch picture elements (touch pixels), such as touch pixels  326  and  327 . This way of understanding can be particularly useful when touch screen  320  is viewed as capturing an “image” of touch. In other words, after touch controller  206  has determined whether a touch has been detected at each touch pixel in the touch screen, the pattern of touch pixels in the touch screen at which a touch occurred can be thought of as an “image” of touch (e.g., a pattern of fingers or other objects touching the touch screen). 
     It should be understood that the row/drive and column/sense associations can be exemplary, and in other examples, columns can be drive lines and rows can be sense lines. In some examples, row and column electrodes can be perpendicular such that touch nodes can have x and y coordinates, though other coordinate systems can also be used, and the coordinates of the touch nodes can be defined differently. It should be understood that touch screen  220  can include any number of row electrodes and column electrodes to form the desired number and pattern of touch nodes. The electrodes of the touch sensor panel can be configured to perform various scans including some or all of row-column and/or column-row mutual capacitance scans, self-capacitance row and/or column scans, row-row mutual capacitance scans, column-column mutual capacitance scans, and stylus scans. The stylus scan can include one or more sub-scans as will be described below. 
     Additionally or alternatively, the touch screen can include touch sensing circuitry including an array of pixelated touch sensors.  FIG. 4  illustrates an example touch screen including touch sensing circuitry configured as pixelated touch sensors according to examples of the disclosure. Touch screen  420  can include touch sensing circuitry that can include a capacitive sensing medium having a plurality of electrically isolated touch sensors, such as touch pixel  422  (e.g., a pixelated touch screen). For example, in a self-capacitance configuration, pixelated touch sensors  422  can be coupled to sense channels in receive circuitry  208  in touch controller  206 , can be driven by stimulation signals from the sense channels (or transmit circuitry  214 ) through drive/sense interface  425 , and can be sensed by the sense channels through the drive/sense interface as well, as described above. Labeling the conductive plates used to detect touch (i.e., pixelated touch sensors  422 ) as “touch pixel electrodes” can be particularly useful when touch screen  420  is viewed as capturing an “image” of touch. In other words, after touch controller  206  has determined an amount of touch detected at each pixelated touch sensor  422  in touch screen  420 , the pattern of pixelated touch sensors in the touch screen at which a touch occurred can be thought of as an “image” of touch (e.g., a pattern of fingers or other objects touching the touch screen). The pixelated touch screen can be used to sense mutual capacitance and/or self-capacitance. It should be understood that touch screen  220  can include any number of pixelated touch sensors to form the desired number and resolution of touch sensors. The electrodes of the touch sensor panel can be configured to perform various scans including some or all of mutual capacitance scans, self-capacitance scans, and stylus scans. The stylus scan can include one or more sub-scans as will be described below. 
     As described herein, in addition to performing touch scans to detect an object such as a finger or a passive stylus, computing system  200  can also perform stylus scans to detect an active stylus and can communicate with a stylus. For example, an active stylus can be used as an input device on the surface of a touch screen of touch-sensitive device.  FIG. 5  illustrates an example active stylus according to examples of the disclosure. Stylus  500  can include one or more electrodes  502 , which can be located, for example, at a distal end of the stylus (e.g., the tip of the stylus). As illustrated in  FIG. 5 , stylus  500  can include a tip electrode  501  and a ring electrode  503 . Tip electrode  501  can include a material capable of transmitting the stylus stimulation signal from stylus stimulation circuitry  504  to the touch-sensitive device, such as a flexible conductor, a metal, a conductor wrapped by a non-conductor, a non-conductor coated with a metal, a transparent conducting material (e.g., indium tin oxide (ITO)) or a transparent non-conductive material (e.g., glass) coated with a transparent (e.g., ITO) or opaque material, or the like. In some examples, the stylus tip can have a diameter of 2 mm or less. In some examples, the stylus tip can have a diameter between 1 mm and 2 mm. Ring electrode  503  can include a conductive material, such as a flexible conductor, a metal, a conductor wrapped by a non-conductor, a non-conductor coated with a metal, a transparent conducting material (e.g., ITO) or a transparent non-conductive material (e.g., glass) coated with a transparent (e.g., ITO) or opaque material, or the like. In some examples, a transparent stylus tip and/or ring electrode can be used for projection purposes. 
     Stylus  500  can also include stylus stimulation circuitry  504 . Stylus stimulation circuitry  504  can be configured to generate one or more stylus stimulation signals at the one or more electrodes  502  to stimulate a touch-sensitive device. For example, stylus stimulation signals can be coupled from stylus  500  to the touch sensing circuitry of touch screen  220 , and the received signals can be processed by the touch ASIC  201 . The received signals can be used to determine a location of active stylus  500  at the surface of touch screen  220 . In some examples, the received signals can include encoded data. Host device  200  can perform stylus scans, as will be described below, to receive the stimulation signals and decode the data. 
     The operation of stylus stimulation circuitry  504  can be controlled by a processor  506 . For example, the processor can be configured to communicate with the stylus stimulation circuitry to control the generation of stimulation signals. In some examples, the communication between the processor and stylus stimulation circuitry can be accomplished via an SPI bus, and the stylus stimulation circuitry can operate as an SPI slave device. In some examples, the stylus  500  can include more than one processor, and stylus stimulation circuitry  504  can include one or more processors. In some examples, one or more of the stylus functions described herein can be performed by firmware stored in memory or in program storage (not shown) and executed by processor  506  or a processor in stylus stimulation circuitry  504 . In some examples, processor  506  can encode data into one or more stylus stimulation signals generated by stylus stimulation circuitry  504 . The data can be frequency modulated, phased modulated, amplitude modulated or encoded in some other way. In some examples, the data can be indicative of a status of one or more buttons/and or sensors  508  as will be described below. In some examples, the data can be indicative of a status of the stylus itself or be used to establish a wireless communication channel (e.g., BLUETOOTH) between stylus  500  and host device  200 . 
     In some examples, stylus  500  can also include one or more buttons and/or sensors  508 . In some examples, buttons and/or sensors  508  can include a force sensor to detect the amount of force at the tip of the stylus  500 . For example, when the stylus tip is touching touch screen  220 , the force sensor can measure the force at the stylus tip. Information from one of the one or more sensors and/or buttons  508  can be stored in the stylus (e.g., in a memory (not shown)) and/or transmitted (via a wired connection or via a wireless communication channel) to the computing system  200 . For example, the information can be communicated to host processor  228  or touch ASIC  201  in computing system  200 . Sensor and/or button information and corresponding location information can be processed together by host processor  228  and/or touch ASIC  201 . 
     In some examples, the one or more buttons and/or sensors  508  can be coupled to processor  506 . Processor  506  can process information from the one or more buttons and/or sensors  508  and, based on the force information, control stylus stimulation circuitry  504  to generate or not generate stylus stimulation signals. For example, the processor can cause stylus stimulation circuitry  504  to generate no stylus stimulation signals when no force is detected or when the force is below a threshold level. When a force (or a force at or above the threshold level) is detected (e.g., corresponding to touch-down of the stylus), the processor can cause stylus stimulation circuitry  504  to generate stylus stimulation signals and continue generating stylus stimulation signals until the detected force drops below the threshold level (or some other threshold level). In some examples, stylus stimulation circuitry  504  can generate stylus stimulation signals indicative of a status of the one or more sensors and/or buttons  508 . For example, the data can be encoded in the stylus stimulation signals as discussed above. 
     Stylus  500  can also include a wireless communication circuit  510 , although in some examples the wireless communication functionality can be incorporated into other modules within the stylus  500 , and in other examples the stylus can communicate via a wired connection. Wireless communication circuit  510  can transmit the button and sensor information from the stylus  500  to the wireless communication circuitry of computing system  200  via a wireless communication channel (e.g., BLUETOOTH). The wireless communication circuit  510  can also receive other information including, but not limited to, information about stylus stimulus frequencies, scan plan information (i.e., the sequence of scans to be performed by the touch-sensitive device) and clock synchronization information. In some examples, information, such as information about stylus stimulation frequencies and scan event plans, can be transmitted from touch ASIC  201  to the wireless communication unit of computing system  200  via host processor  228 . In other examples, information, such as clock synchronization information, can be communicated directly from touch ASIC  201  to wireless communication unit of computing system  200 . 
       FIG. 6  illustrates an example touch sensor panel configuration operable with the touch ASIC of  FIG. 2  to perform a stylus scan according to examples of the disclosure. During a stylus scan, one or more stimulation signals can be injected by stylus  604  proximate to one or more touch nodes  606 . The stimulation signals injected by stylus  604  can create capacitive coupling Cxr between the stylus  604  and one or more row traces  601  and capacitive coupling Cxc between the stylus  604  and one or more column traces  602  corresponding to the one or more proximate touch nodes  606 . The capacitive coupling Cxr and Cxc between the stylus  604  and the one or more touch nodes  606  can vary based on the proximity of stylus  604  to the one or more touch nodes  606 . During the stylus scan, the transmit circuitry  214  can be disabled, i.e., no stimulation signals Vstim from the touch controller are sent to touch sensor panel  600 . The capacitive coupling (e.g., mutual capacitance) can be received by the receive circuitry  208  from the row and column traces of the one or more touch nodes  606  for processing. As described herein, in some examples the one or more stylus stimulation signals can have one or more frequencies indicative of or encoding a status of a sensor (e.g., a force sensor, motion sensor, orientation sensor), a button or switch, and/or a status of the stylus itself (e.g., battery life). 
     In some examples, one or more multiplexers can be used to couple row and/or column electrodes to the receive circuitry and/or transmit circuitry. For example, during a mutual capacitance touch sensing scan, row traces can be coupled to the transmit circuitry and column traces can be coupled to the receive circuitry. During a stylus sensing scan, column traces (or row traces) can be coupled via the one or more multiplexers to the receive circuitry to detect input from a stylus or other input device along one axis of the touch screen, and then the row traces (or column traces) can be coupled via the one or more multiplexers to the receive circuitry to detect input from a stylus or other input device along a second axis of the touch screen. The detected input can be used to determine the location of contact between a stylus or other input device and the touch sensor panel. In some examples, the row and column traces can be sensed simultaneously (i.e., both row and column traces concurrently coupled to the receive circuitry). In some examples, the stylus can be detected on the column traces concurrently with the mutual capacitance scan touch sensing scan. The touch and stylus signals can be differentiated by filtering and demodulating the received response signals at different frequencies. In some examples, a subset of detected input can be sampled therefrom and data encoded in a stylus stimulation signal can be detected and decoded, as will be described below. 
       FIG. 7  illustrates an example touch sensor panel configuration operable with the touch ASIC of  FIG. 2  to perform a stylus scan according to examples of the disclosure. For example, a stylus  702  can provide an input to touch sensor panel  700 . In some examples, a touch sensor panel, such as touch sensor panel  700 , can include an array of electrically isolated pixelated touch sensors  710 , similar to pixelated touch sensor  422 . During a stylus scan, one or more stimulation signals injected by stylus  702  can create capacitive coupling Cx between the stylus  702  and a touch sensor  712  included in panel  700 . The capacitive coupling Cx between the stylus  702  and the touch sensors  710  can vary based on the proximity of stylus  702  to the touch sensors  710 , for example. During the stylus scan, the transmit circuitry  214  can be disabled as described above, for example. In some examples, one or more stylus stimulation signals can have one or more frequencies indicative of or encoding a status of a sensor (e.g., a force sensor, motion sensor, orientation sensor), a button or switch, and/or a status of the stylus itself (e.g., battery life). 
     In some examples, one or more multiplexers can be used to couple one or more touch sensors of the array of touch sensors to receive and/or transmit circuitry. For example, to sense touch from a finger or passive stylus, one or more touch sensors can be stimulated and sensed. A resulting change in the self-capacitance to ground can indicate an object touching or proximate to the one or more touch sensors, for example. During a stylus scan, one or more touch sensors can be coupled via one or more multiplexers to receive circuitry to detect input from a stylus or other input device at the touch screen. The detected input can be used to determine the location of contact and/or proximity between a stylus or other input device and the touch sensor panel. In some examples, a subset of detected input can be sampled therefrom and data encoded in a stylus stimulation signal can be detected and decoded, as will be described below. 
     In summary, during a stylus scan, the transmit circuitry  214  can be disabled, i.e., no stimulation signals Vstim are sent to a touch sensor panel, according to the examples described with reference to  FIGS. 1-4 and 6-7 , while some or all of the touch sensors can be coupled to the receive circuitry. In some examples, touch sensors can be arranged as intersecting rows and columns, such as the examples of  FIGS. 3 and 6 . In some examples, touch sensors can be arranged in a pixelated array, such as the examples of  FIGS. 4 and 7 . The receive circuitry  208  can receive and process stylus signals from some or all of the touch sensors of the touch sensor panel in order to determine a location of the stylus. In some examples, a subset of touch sensors can also be sampled to collect encoded data in the stylus stimulation data, as will be described in more detail below. 
     In addition to communicating via a capacitive channel (e.g., through stylus signals received at one or more touch sensors), in some examples, an input device (e.g., stylus) and a host device can communicate over a wireless communication channel, such as BLUETOOTH, WIFI or any other suitable protocol. One or more of these communication methods may require an initial “pairing” operation before data can be exchanged. In some examples, a wired connection can be used to perform a pairing operation.  FIG. 8  illustrates an example pairing operation  800  between a stylus  810  and a host device  820  via a wired connection  830  according to examples of the disclosure. Once connected via wired connection  830 , data can be exchanged between the stylus  810  and the host device  820  to establish a wireless communication channel. After pairing is complete, wired connection  830  can be terminated and stylus  810  and host device  820  can communicate via a wireless communication channel. 
     In some examples, the pairing operation can be performed without a wired connection between the stylus and host device. For example, when the stylus  500  is not paired with computing system  200 , the stylus can transmit information for setting up a wireless communication channel (e.g., BLUETOOTH, WIFI, etc.) via stimulation signals received at the touchscreen to the computing system  200 . The information for setting up the wireless communication channel can be encoded in the stylus stimulation signals. Once the wireless communication channel has been established, the stylus can stop encoding and transmitting the pairing information. The stylus  500  can produce a plurality of stimulation frequencies to transmit frequency-encoded data, for example. In some examples, other encoding schemes, such as phase modulation and/or amplitude modulation, are possible. 
     In some examples, a wireless communication channel can be used to transmit data from one or more sensors (e.g., a force sensor, motion sensor, orientation sensor) of the stylus, a status of one or more switches included in the stylus, and/or a status of the stylus  810  itself. For example, a battery life of the stylus  810  can be transmitted. While using a wireless communication channel for data transmission, the host device  820  can receive stimulation signals from the stylus  810  via a plurality of capacitive touch sensors. Although receiving data through a dedicated wireless communication channel can simplify the hardware of the touch sensitive display, as data receive channels and decoders are not necessary, user experience can suffer due to high latency of data transmission. For example, a user may apply various amounts of force while drawing a line with stylus  810  on the surface of host device  820  to change a thickness of the line. When there is high latency caused by a wireless communication channel between stylus  810  and host device  820 , the user can experience a delay between drawing a line and observing the line&#39;s thickness change. Additionally, using a wired connection  830  for pairing requires user action before a wireless communication channel can be established. 
     In some examples, an active stylus can encode data in a stimulation signal received by a host device. The data can include information for setting up a wireless communication channel (e.g., BLUETOOTH) with the host device, replacing the need for a wired setup as described above with reference to  FIG. 8 . Performing a pairing operation via stylus stimulation signals can be more convenient for a user of the stylus and host device than pairing via a wired connection, thereby providing a seamless and intuitive user experience. In some examples, once a wireless communication channel is established, the host device and the stylus can exchange data via a two-way communication channel. The data can include data from one or more sensors of the stylus, a status of the stylus (e.g., battery life), or other data. In some examples, this data can be encoded in the stylus stimulation signal for one-way communication from the stylus to the host device. In some examples, transferring data by encoding it in a stimulation signal can be faster than transferring data through a two-way wireless communication channel such as Bluetooth. Additionally, transferring data by encoding it in a stimulation signal can provide for improved processing of the data with stylus location information by reducing the latency between receipt of the data (e.g., force) and stylus location information. In some examples, some data can be transferred both through the capacitive interface using stylus stimulation signals and some data via a wireless communication channel such as BLUETOOTH. For example, time-sensitive data can be transferred through the capacitive interface (e.g., force or tilt data can be provided via the capacitive interface along with location information to enable co-processing), where other types of data can be transferred via the wireless communication channel (e.g., stylus battery power state). 
     In some examples, a stylus can transmit encoded data via a stylus stimulation signal. The signal can be sampled by the host device at one or more capacitive touch sensors, such as those described above. In some examples, different circuitry can be used to decode stylus data and to detect the presence and location of a stylus. In some examples, each sense channel of the receive circuitry can include decoding circuitry (a decoding channel) configured to decode stylus data. Decoding circuitry for each sense channel, however, can add cost and increase power and/or space consumption for the receive circuitry. Alternatively, fewer decoding circuits or channels can be used in some examples. For example, the touch sensors can be coupled to the fewer decoding channels or the signals sampled from the touch sensors can be combined (e.g., averaged) before processing by the decoding channels. Coupling or otherwise combining touch sensors or signals from touch sensors can reduce hardware requirements, but can be detrimental to SNR. In some examples, fewer decoding channels can be used while also preserving SNR, by intelligently selecting a subset of touch sensors (or sense channels measuring the subset of touch sensors) proximate to the stylus during data transmission to be sampled and decoded by decoding circuitry, as will be described below. Although often described herein as implemented using hardware, in some examples the decoding function can also be performed using firmware or software. 
     In some examples, a host device can perform a stylus scan including multiple sub-scans to locate a stylus and receive data encoded in the stylus&#39; stimulation signal. During one or more coarse stylus sub-scans, the host device can determine a coarse image of stylus touch for the touch panel and determine a coarse location of the panel at which the stylus can be located.  FIGS. 9A-9C  illustrate exemplary coarse stylus sub-scans according to examples of the disclosure. In  FIG. 9A , an exemplary touch sensing system can perform a coarse stylus sub-scan of an array of pixelated touch sensors (e.g., sensor  912 ) forming touch sensor panel  910  to determine an approximate location of stylus  920 . In some examples, the touch sensing system can couple multiple pixelated touch sensors (e.g., touch sensors  912 ) of touch sensor panel  910  into larger groups (e.g., region  914 ) to be scanned by sense channels, for example. During a coarse stylus sub-scan, the touch sensing system can determine a coarse location of stylus  920  to be within one of the groups of sensors (e.g., a region of touch sensor panel  910 ), for example. Once the stylus  920  is coarsely located, the touch sensing system can perform a fine stylus sub-scan to determine stylus location with more particularity and/or to receive encoded data, for example. 
     In some examples, data encoded in a stylus signal can be detected by a touch sensor panel including touch sensors arranged in intersecting rows and columns.  FIG. 9B  illustrates an exemplary touch sensing system performing a coarse stylus sub-scan in a first dimension of touch sensor panel  940 , for example. In  FIG. 9B , touch sensors disposed in rows can be sensed, and therefore the sub-scan can also be referred to as a coarse stylus row sub-scan. In some examples, touch sensor panel  940  can receive stimulation signals from active stylus  950 . During a coarse stylus row sub-scan, touch sensor panel  940  can couple a plurality of touch sensors (e.g., sensor  942 ) disposed in rows into groups (e.g., group  944 ) to be sensed by sense channels, for example. In some examples, the coarse stylus row sub-scan can include sampling a self-capacitance of one or more touch sensor groups included in touch sensor panel  940  to determine a coarse location of active stylus  950  in one sensor group, for example. Once the stylus  950  is located coarsely in one dimension (along the rows), the touch sensing system can perform a fine stylus sub-scan in one dimension (or fine stylus row sub-scan) to determine stylus location with more particularity and to receive encoded data, for example. In some examples, a fine stylus row sub-scan can include sampling a self-capacitance of touch sensors arranged in rows individually or in smaller groups than scanned during the coarse stylus row sub-scan. In some examples, a fine stylus row sub-scan can include sampling a self-capacitance of touch sensors in the identified group of touch sensors proximate to the stylus  950 . In either example, the fine stylus row sub-scan can include sampling and decoding data from the touch sensors in the identified group. By decoding data from a subset of touch sensors proximate to active stylus  950 , a small number of decoder channels can be provided while also preserving signal integrity and signal to noise ratio (SNR). Methods and hardware for sampling and decoding encoded stylus data will be described. 
       FIG. 9C  illustrates an exemplary touch sensor panel  970  performing a coarse detection scan in a second dimension, for example. In  FIG. 9C , touch sensors disposed in columns can be sensed, and therefore the sub-scan can also be referred to as a coarse stylus column sub-scan. In some examples, touch sensor panel  970  can receive stimulation signals from active stylus  980 . During a coarse stylus column sub-scan, touch sensor panel  970  can couple a plurality of touch sensors (e.g., sensor  972 ) disposed in columns into groups (e.g., group  974 ) to be sensed by sense channels, for example. In some examples, the coarse stylus column sub-scan can include sampling a self-capacitance of one or more touch sensor groups included in touch sensor panel  970  to determine a coarse location of active stylus  980  in one sensor group, for example. Once the stylus  980  is located coarsely in one dimension (along the columns), the touch sensing system can perform a fine stylus sub-scan in one dimension (or fine stylus column sub-scan) to determine stylus location with more particularity and to receive encoded data, for example. In some examples, a fine stylus column sub-scan can include sampling a self-capacitance of touch sensors arranged in rows individually or in smaller groups than scanned during the coarse stylus column sub-scan. In some examples, a fine stylus column sub-scan can include sampling a self-capacitance of touch sensors in the identified group of touch sensors proximate to the stylus  980 . In either example, the fine stylus column sub-scan can include sampling and decoding data from the touch sensors in the identified group. By decoding data from a subset of touch sensors proximate to active stylus  980 , a small number of decoder channels can be provided while also preserving signal integrity and improving a signal to noise ratio (SNR). Methods and hardware for analyzing encoded stylus data will be described. 
     To continue to track the location of a powered stylus and collect encoded data from a stylus signal at one or more touch sensors proximate to the stylus tip, a touch sensor panel can perform a sequence of the above described stylus sub-scans, for example.  FIG. 10  illustrates an example timing diagram  1000  for stylus activity  1002  and touch sensor panel activity  1004 , according to examples of the disclosure. In some examples, an active stylus can use frequency modulation to transmit encoded data to a host device. Stylus signal  1002  includes a transmission at a first frequency f 0  and a transmission at a second frequency f 1 , for example. In some examples, two frequencies can be used to transmit data in a binary code. In some examples, a stylus signal  1002  can include more than two different frequencies to encode data. 
     A touch sensing system (e.g., touch controller) can perform various types of stylus sub-scans according to timing  1004 , for example. In some examples, one or more coarse detection sub-scans, such as a coarse stylus row sub-scan (“ROW DETECT”) or coarse stylus column sub-scan (“COLUMN DETECT”) can be used to coarsely detect stylus location along one or both axes. In some examples, one or more fine detection sub-scans, such as fine stylus row sub-scan (“ROW FREQ. ESTIMATION &amp; POSITION”) and fine stylus column sub-scan (“COL FREQ. ESTIMATION AND POSITION”) can be performed to finely track stylus location and to decode stylus signals at sensors proximate to the determined stylus location. In some examples, a coarse stylus location along a group of rows can be detected during “ROW DETECT”. Once the stylus is coarsely located, a plurality of sensors proximate to the stylus (e.g., those within the group and/or proximate to the group) can be sampled for further analysis during “ROW FREQ. ESTIMATION &amp; POSITION,” for example, to determine a fine location of the stylus along the rows and/or decode data encoded in the stylus stimulation signals. A coarse stylus location along a group of columns can be similarly detected during “COL DETECT,” and selected columns (e.g., those within the group and/or proximate to the group) can similarly be sampled during “COL FREQ. ESTIMATION &amp; POSITION,” for example, to determine a fine location of the stylus along the columns and/or decode data encoded in the stylus stimulation signals. In some examples related to a touch sensor panel including a pixelated array of touch sensors, a two-dimensional coarse stylus sub-scan can be performed to determine a coarse location of the stylus followed by a fine stylus sub-scan to determine a fine location of the stylus and/or decode data encoded in the stylus stimulation signals. 
     It should be understood that the sequence of stylus sub-scans in  FIG. 10  is exemplary. In some examples, COL DETECT followed by COL FREQ. ESTIMATION &amp; POSITION can be performed before ROW DETECT and ROW FREQ. ESTIMATION &amp; POSITION. In some examples, ROW DETECT and COL DETECT can be performed followed by ROW FREQ. ESTIMATION &amp; POSITION and COL FREQ. ESTIMATION &amp; POSITION. In some examples, encoded data can be transmitted/decoded during only one ROW FREQ. ESTIMATION &amp; POSITION or COL FREQ. ESTIMATION &amp; POSITION. In other examples, as described above, encoded data can be transmitted/decoded during each of the ROW FREQ. ESTIMATION &amp; POSITION and COL FREQ. ESTIMATION &amp; POSITION. In some examples, one or more fine stylus sub-scans, such as COL FREQ. ESTIMATION &amp; POSITION and/or ROW FREQ. ESTIMATION &amp; POSITION, can be repeated without interleaving a coarse scan, such as ROW DETECT and/or COL DETECT, in between. 
     The sequence of stylus sub-scans (e.g., as illustrated in  FIG. 10 ) can be performed continuously (e.g., once per stylus sensing frame). In some examples, the sequence of stylus sub-scans can be performed periodically (e.g., every N sensing frames, once per second, etc.). In some examples, when a coarse stylus sub-scan fails to detect a stylus, the fine stylus sub-scans can be aborted. Analysis of collected stylus data will be described below. 
     In some examples, a touch sensing system can perform additional scans interleaved with the stylus sub-scans described above. In some examples, a touch sensing system can perform touch detection scans for detecting a touch or hover of a finger or other conductive object. Unlike a powered stylus, a finger or other conductive object may not produce a stimulation signal to be coupled to one or more touch sensors included in a touch sensor panel. Therefore, in some examples, the one or more touch detection scans can include applying a stimulation signal to sense a mutual or self-capacitance of one or more touch sensors. Touch scans can include a coarse touch detection scan and a fine touch detection scan to determine a coarse and fine location of a conductive object, for example. In some examples, the coarse and fine touch scans can include coupling one or more touch sensors to a stimulation signal. 
     In some examples, a fine stylus scan can be any stylus scan that provides information about stylus touch events with a higher resolution than a given corresponding coarse stylus scan (i.e., a fine stylus row sub-scan can be higher resolution than a corresponding coarse stylus row sub-scan, and a fine stylus column sub-scan can be a higher resolution than a corresponding coarse stylus column sub-scan). As described herein, resolution of a scan can be understood in terms of the number of capacitive measurements representing a corresponding group of electrodes of a touch sensor panel. For example, self-capacitance for a 4×4 array of touch nodes (16 touch nodes) can be represented by 16 self-capacitance measurements (e.g., one self-capacitance measurement for each node measured by a sense channel), 4 self-capacitance measurements (e.g., one self-capacitance measurement for groups four nodes each measured by a sense channel), or a single self-capacitance measurement (e.g., one self-capacitance measurement for a group of all the nodes coupled to a single sense channel). These numbers of measurements are only exemplary, but it is understood that 16 self-capacitance measurements for 16 touch nodes can provide higher resolution (finer detail) than 4 measurements or a single measurement, respectively. Likewise, mutual capacitance for a 4×4 array of touch nodes (16 touch nodes) can be represented by 16 mutual capacitance measurements (e.g., four mutual capacitance measurements for each group of 4 electrodes, with each electrode in the group acting as a sense electrode), 8 mutual capacitance measurements (e.g., two mutual capacitance measurements for each group of 4 electrodes, with two of the electrodes in the group acting as a sense electrode), 4 mutual capacitance measurements (e.g., one mutual capacitance measurement for each group of 4 electrodes, with one electrode in the group acting as a sense electrode), or a single mutual capacitance measurement (e.g., one mutual capacitance measurement for all 16 electrodes, with a group of electrodes acting as a sense electrode coupled to one sense channel). These numbers of measurements are only exemplary, but it is understood that 16 mutual capacitance measurements for 16 touch nodes can provide higher resolution (finer detail) than 4 measurements or a single measurement, respectively. 
     In some examples, a touch sensitive device can include circuitry for analyzing encoded stylus data. In some examples, analysis can be performed using hardware, software, or firmware.  FIG. 11A  illustrates exemplary stylus signal analysis hardware  1100  for decoding stylus data according to examples of the disclosure. Stylus signal analysis hardware  1100  can be used to analyze collected data from one or more touch sensors proximate to a stylus during a fine stylus sub-scan, as described above, for example. In some examples, once stylus location is coarsely determined, proximate touch sensors (or sense channels measuring proximate touch sensors) can be selected at multiplexers  1110 , for example. During a fine stylus sub-scan, stylus location can be more finely resolved and a subset of sensors proximate to the stylus (e.g., as determined by the coarse stylus sub-scan) can be selected to sample encoded data. In some examples, coarsely and finely resolving stylus location can include generating an “image of touch” representative of stylus presence at the touch sensor panel. In some examples, selecting one or more touch sensors using multiplexers  1110  based on an image of touch can be advantageous over receiving stylus data at all touch sensors on a panel, as described above. For example, providing a dedicated decoding channel for receiving and decoding stylus data for each sense channel can be expensive from a hardware perspective (cost, power, area, etc.). Instead, fewer decoding channels can be used, and the touch sensors (or sense channels) to sample for decoding stylus data can be intelligently selected using multiplexers  1110 . Fewer decoding channels can reduce hardware requirements (reducing cost, power, and area) and meet SNR requirements for the decoding channels, for example. 
     In examples where a powered stylus encodes data using frequency modulation, a spectrum can be determined for received data at correlation engines  1120 .  FIG. 11B  illustrates an exemplary correlation engine  1120  in detail according to examples of the disclosure. In some examples, correlation engines  1120  can include a plurality of demodulators  1122 , and each demodulator can be configured to demodulate a received signal at a selected frequency. In some examples, multiple frequencies, such as f 1 -f 5  illustrated in  FIGS. 11A-11B , can be selected corresponding to a range of frequencies the stylus can use to encode data. It should be understood that a fewer or more frequencies can be provided to encode data. Although correlation engine  1120  is illustrated including demodulators  1122  to demodulate frequency-encoded data, other hardware can be included to process a stylus signal including data encoded in a different way. For example, demodulators  1122  can be provided with a plurality of signals with different phases to determine a phase of a received signal including phase-encoded data. In some examples, a plurality of comparators can be provided, each one coupled to a signal with a different amplitude to determine an amplitude of a received signal including amplitude-encoded data. The results  1124  of each of the demodulators  1122  can be stored in buffers  1126  and  1127  to capture and analyze several frames of data, for example. In some examples, demodulating a received signal with multiple demodulators across a range of frequencies can determine a frequency spectrum of a stylus stimulation signal. By determining and storing transmitted frequencies, frequency-encoded stylus data can be decoded. 
       FIG. 12  illustrates an example block diagram of a touch sensing system including position-based data decoding according to examples of the disclosure. The elements of system  1200  can be included, for example, as part of the touch ASIC  201 . In some examples, a stimulation signal can be captured at touch sensors  1210  incorporated into a touch-sensitive display. Touch sensors  1210  can be arranged in intersecting rows and columns, as described with reference to  FIGS. 3, 6 and 9B-9C  for example. Alternatively, in some examples, touch sensors  1210  can be arranged in a pixelated array, as described with reference to  FIGS. 4, 7 and 9A , for example. In some examples, a coarse stylus sub-scan can sample subsets of the touch sensors  1210  in multiple steps using multiplexer  1220 . Collected data can be processed by sense channels  1230 , for example. In some examples, each sense channel can include an amplifier  1232  and an analog-to-digital converter (ADC)  1234 . In some examples, other components can be included in sense channels  1230  (e.g., anti-aliasing filters). Sense channels  1230  can be implemented using hardware, software, firmware, or a combination thereof. The outputs of sense channels  1230  can be processed by digital signal processing units (DSPs)  1240 , for example. DSPs  1240  can perform operations such as filtering and determining changes in capacitance at each touch sensor  1210 , for example. To determine changes in capacitance at the touch sensors  1210 , DSPs  1240  can include demodulators (not shown). The demodulators can perform digital demodulation on the output of the ADCs. The demodulators can also include a programmable or non-programmable delay to align the phase of the ADC output with the demodulation waveform, a mixer (e.g., signal multiplier) to mix the ADC output with the demodulation waveform, and an accumulator (e.g., an integrator) to accumulate the output from mixer. Although not shown, the accumulated output from the integrator can be scaled, decoded (e.g., in multi-stim touch sensing schemes) to generate result which can be stored in a memory (e.g., RAM  212 ) for further processing. 
     In some examples, the outputs from the DSPs  1240 , taken together, can be viewed as an “image of touch”  1250 , indicative of which location(s) on the panel a stylus (and/or finger) is touching. Based on an image of touch  1250 , a position estimation engine  1260  can select one or more touch sensors  1210  (or sense channels  1230 ) proximate to the stylus, in some examples. Position estimation engine  1260  can be a dedicated processor or other hardware component or software or firmware executed by a multi-purpose processor, such as touch processor(s)  202 , for example. In some examples, position estimation engine  1260  can be a combination of firmware or software and hardware or a state machine. In some examples, the position estimation engine  1260  can select one or more touch sensors  1210  (or sense channels  1230 ) to use for stylus data sampling. The output of the selected one or more sensors can be coupled to multiplexers  1270  for further processing and decoding. In some examples, data collection at sense channels  1230  is not limited to sampling the selected one or more sensors. Touch and/or stylus location scanning can continue for all or part of the panel while selected sense channels are additionally sampled to decode stylus data, for example. Signals selected by multiplexers  1270  can further be analyzed by stylus data processing hardware  1280  to decode data encoded in a stylus stimulation signal, for example. In some examples, each multiplexer of the plurality of multiplexers  1270  can be routed to all ADC outputs to select one sense channel among all sense channels on the panel. In some examples where a plurality of channels are selected to be analyzed at the same time, the multiplexers  1270  may be wired using fewer connections. For example, if the system analyzes data from three sense channels in parallel, each multiplexer  1270  may select one sense channel of one third of all sense channels incorporated into the panel, as no two multiplexers  1270  would need to simultaneously select the same channel. Dividing the available sense channels into groups such that each sense channel can only be selected by a subset of the plurality of multiplexers  1270  can reduce the number of connections needed between the ADC outputs and the multiplexers. In some examples, stylus data processing hardware  1280  can include one or more correlation engines  1120  for determining a frequency spectrum of a received signal. In some examples, one or more of position estimation engine  1260 , multiplexers  1270 , and stylus data processing hardware  1280  can reside on a dedicated hardware device that can be coupled to an existing touch-sensing system. 
     In some examples, a dedicated hardware block can be provided to analyze data encoded in a stylus stimulation signal, such as stylus data processing hardware  1280 . Using hardware to process the stylus data can reduce latency between a user action (e.g., applying force, toggling a button or switch, etc.) and a response by the host device associated with the action, for example. In some examples, however, software or firmware can be used to analyze stylus stimulation signals.  FIGS. 13A-13B  illustrate exemplary stylus data processing hardware  1310  and  1350  according to examples of the disclosure. In some examples, stylus data processing hardware  1310  can receive input  1312  selected by position estimation engine  1260  via multiplexers  1270 .  FIG. 13A  illustrates an example stylus data processing hardware unit  1310  including a plurality of correlation engines  1316  according to examples of the disclosure. In some examples, each channel of data can be input to a separate correlation engine  1316 . Correlation engines  1316  can be hardware components similar to correlation engine  1120  and/or implemented in software or firmware (e.g., executed by touch processor  202 ). The resulting frequency spectrums from correlation engines  1316  can be input to adder  1318  to determine an estimated frequency of a stylus stimulation signal. It should be understood that adder  1318  is merely one example of a function used to combine the frequency spectrums from the correlation engines  1316 . In some examples, a median, a maximum SNR, a maximum peak signal, or other function may be computed to select the data to be decoded. The stylus stimulation frequency can be used to decode data encoded by the stylus, for example.  FIG. 13B  illustrates an example stylus data processing hardware unit  1350  that can sum selected signals  1352  before determining a spectrum with correlation engine  1356 . Selected signals  1352  may be provided by a position estimation engine  1260  via multiplexers  1270 , for example. In some examples, correlation engine  1356  may be implemented using hardware similar to correlation engine  1120  and/or implemented using software or firmware (e.g., executed by touch processor  202 ). By summing input signals  1352  before performing spectral analysis with correlation engine  1356 , fewer correlation engines can be included in stylus data processing hardware  1350  thereby reducing hardware requirements (area, power, cost), for example. Stylus processing hardware  1310 , however, can have an improved SNR compared with stylus processing hardware  1350  because correlation is performed before summing, whereas stylus processing hardware  1350  sums the noise from the inputs first before correlation. As a result, a plurality of correlation engines  1316  can reduce frequency content resulting from noise, for example. 
     In some examples, a combination of stylus processing hardware  1310  and stylus processing hardware  1350  can be used. For example, stylus data from multiple groups of selected touch sensors can be summed and then analyzed with one or more correlation engines. For example, nine touch sensors (or sense channels) proximate to the stylus can be selected and coupled into three groups of three sensors prior to demodulation. In this example, the three frequency spectra (each indicative of a sum of data from three touch sensors) can be summed by an additional adder and then decoded. A multi-staged stylus processing hardware device can produce a tradeoff between SNR and cost, for example. 
       FIG. 14  illustrates an example process  1400  for decoding data included in a stylus stimulation signal according to examples of the disclosure. Process  1400  can be performed by a touch sensing system (e.g., by touch ASIC  201 ). In some examples, process  1400  can include determining a location of a stylus or other input device (e.g., stylus  500 ,  920  or  960 ). For example, the touch sensing system can perform one or more coarse detection scans, such as ROW DETECT and/or COL DETECT described with reference to  FIG. 10  to determine a stylus location. In examples including an array of pixelated touch sensors, such as the examples shown in  FIGS. 4, 7 and 9A , a coarse detection scan can also be performed to coarsely determine stylus location. The coarse location can be used to select touch sensors (or sense channels) to sample to decode stylus data. In some examples, a position estimation engine  1260  can output one or more signals to one or more multiplexers  1270  to select the one or more touch sensors (or sense channels) proximate to the stylus for sampling. At  1420 , the touch sensing system can perform a fine scan to determine a fine stylus location and decode stylus data. The stylus data can be sampled from the selected touch sensors (or sense channels) selected based on the coarse location. At  1430 , the selected signals from the selected touch sensors (or sense channels) can be analyzed (e.g., using stylus data analysis hardware  1280 ,  1310  or  1350 ). Additionally, the signals received from the sense channels can also be processed by the touch sensing system to determine the location of the stylus. In some examples, firmware or software (e.g., executed by processor  202 ) can be used for the stylus data analysis. In some examples, the data can be analyzed using one or more correlation engines  1120  including a plurality of demodulators  1122 . The resulting demodulation  1124  can be used to determine a frequency spectrum of a stylus signal, for example. In some examples, the spectral analysis of the stylus data analysis hardware can be implemented in software or firmware to be executed by one or more processors (e.g., touch processor  202 ). For example, a frequency spectrum can be determined algorithmically (e.g., using FFT or one or more other known algorithms). In some examples, other data processing can be performed to decode data encoded in other ways. For example, an amplitude of a stylus signal can be determined before decoding amplitude-encoded data. In some examples, a phase of a stylus signal can be determined before decoding phase-encoded data. In general, many possible signal processing techniques to extract the desired information could be devised to decode data encoded in phase, frequency, amplitude, position, pulse width, waveform cross-section, spread-spectrum signature, etc. At  1440 , stylus data can be decoded. For example, a frequency of a stylus stimulation signal can be determined to decode frequency-modulated data. In some examples, other methods of decoding/encoding are possible. For example, a stylus may use phase modulation, amplitude modulation, or another encoding scheme. In some examples, after decoding stylus data, data from the selected touch sensors can be used to re-estimate stylus location for a next stylus scan. In some examples, a new coarse detection scan can be performed to determine stylus location for the next stylus scan. Process  1400  can be repeated while a stylus is detected at a host device. 
     Therefore, according to the above, some examples of the disclosure are directed to a touch-sensitive device. The touch-sensitive device can comprise a plurality of sense channels configured to receive signals from an input device at a plurality of touch sensors; a plurality of digital signal processors coupled to outputs of the plurality of sense channels, the plurality of digital signal processors including a plurality of first demodulators configured to demodulate the received signals; a position estimation processor configured to estimate a location of the input device based on a first plurality of received signals processed by the plurality of digital signal processors, and configured to select a subset of the plurality of sense channels coupled to one or more touch sensors proximate to the input device based on the estimated location of the input device; and one or more correlators couplable to the selected subset of the plurality of sense channels. The one or more correlators can comprise a plurality of second demodulators. The second demodulators can be configured to demodulate a second plurality of received signals from the selected subset of the plurality of sense channels. The one or more correlators can be configured to determine frequency content of the demodulated signals. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch-sensitive device can further comprise one or more multiplexers configured to receive a signal indicative of the selected subset of the plurality of sense channels from the position estimation processor and couple the selected subset of the plurality of sense channels to the one or more correlators. Additionally or alternatively to one or more of the examples disclosed above, in some examples, a correlator of the plurality of correlators can further comprise an adder coupled to a plurality of outputs of the second demodulators, and the correlator can be configured to determine the frequency content of an output of the adder. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first plurality of received signals can be received while the touch-sensitive device is configured in a first configuration, the first configuration including coupling two or more touch sensors of the plurality of touch sensors to each sense channel. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the second plurality of received signals can be received while the touch-sensitive device is configured in a second configuration, the second configuration including coupling one touch sensor of the plurality of touch sensors to each sense channel. 
     Other examples of the disclosure are directed to a method for decoding data transmitted by an input device. The method can comprise: receiving signals from the input device; estimating a location of the input device relative to a touch sensitive surface based on a first plurality of received signals; selecting one or more sense channels coupled to the touch sensitive surface based on the estimated location of the input device, the one or more selected sense channels sensing touch sensors of the touch sensitive surface proximate to the input device; and decoding encoded data from a second plurality of signals received at the selected one or more sense channels. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method can further comprise demodulating the second plurality of signals with a plurality of demodulators. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method can further comprise determining frequency content of the demodulated second plurality of signals. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method can further comprise determining one of a sum, a median, a maximum peak, and a maximum signal-to-noise ratio of the demodulated second plurality of signals. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method can further comprise receiving the first plurality of received signals during a first operation, the first operation comprising coupling two or more touch sensors of the touch sensitive surface to each sense channel. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method can further comprise receiving the second plurality of received signals during a second operation, the second operation comprising coupling one touch sensor of the touch sensitive surface to each sense channel. 
     Some examples of the disclosure are directed to a non-transitory computer readable storage medium. The computer readable medium can store one or more programs, the one or more programs comprising instructions, which when executed by an electronic device including one or more processors, can cause the electronic device to perform a method. The method can comprise receiving signals from an input device; estimating a location of the input device relative to a touch sensitive surface based on a first plurality of received signals; selecting one or more sense channels coupled to the touch sensitive surface based on the estimated location of the input device, the one or more selected sense channels sensing touch sensors of the touch sensitive surface proximate to the input device; and decoding encoded data from a second plurality of signals received at the selected one or more sense channels. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method can further comprise demodulating the second plurality of signals with a plurality of demodulators. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method can further comprise determining frequency content of the demodulated second plurality of signals. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method can further comprise determining one or more of a sum, a median, a maximum peak, and a maximum signal-to-noise ratio of the demodulated second plurality of signals. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method can further comprise receiving the first plurality of received signals during a first operation, the first operation comprising coupling two or more touch sensors of the touch sensitive surface to each sense channel. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method can further comprise receiving the second plurality of received signals during a second operation, the second operation comprising coupling one touch sensor of the touch sensitive surface to each sense channel. 
     Some examples of the disclosure are directed to an apparatus. The apparatus can comprise a position estimation processor configured to estimate a location of the input device based on a first plurality of signals received at a plurality of sense channels, and configured to select a subset of the plurality of sense channels coupled to one or more touch sensors proximate to the input device based on the estimated location of the input device; and one or more correlators couplable to the selected subset of the plurality of sense channels. The one or more correlators can comprise a plurality of demodulators. The demodulators can be configured to demodulate a second plurality of signals from the selected subset of the plurality of sense channel. The one or more correlators can be configured to determine frequency content of the demodulated signals. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the apparatus can further comprise one or more multiplexers coupled to one or more inputs of the correlators. The one or more multiplexors can be configured to: receive a signal indicative of the selected subset of the plurality of sense channels from the position estimation processor and couple the selected subset of the plurality of sense channels to the one or more correlators. Additionally or alternatively to one or more of the examples disclosed above, in some examples, a correlator of the plurality of correlators can further comprise an adder coupled to a plurality of outputs of the demodulators. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first plurality of signals can be received while two or more touch sensors of the plurality of touch sensors are coupled to each sense channel. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the second plurality of signals can be received while one touch sensor of the plurality of touch sensors is coupled to each sense channel. 
     Although examples have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the various examples as defined by the appended claims.

Metadata:
Filing Date: 20160531
Publication Date: 20191112
Grant Date: 20191112
Priority Date: 20160531
Inventors: PANT, VIVEK
MALKIN, MOSHE
SHAHPARNIA, SHAHROOZ
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/03545", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/03545", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0416", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/03545", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0442", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0441", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/041661", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04162", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0442", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0441", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/041661", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04162", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 60417895