Patent Publication Number: US-9898095-B2

Title: Low-profile capacitive pointing stick

Description:
BACKGROUND 
     Field of the Disclosure 
     Embodiments generally relate to input sensing and, in particular, to input sensing using a low-profile capacitive pointing stick. 
     Description of the Related Art 
     Electronic devices, such as computers, can include or be connected to various input devices for interacting with a user. Example input devices include keyboards, pointing devices, proximity sensor devices (also commonly called touchpads or touch sensor devices), and the like. Both a pointing device and a touchpad can be used to provide input interfaces to the electronic device. For example, a pointing device and/or touchpad allow the user to move a cursor or other type of user interface indicator on a display. A “pointing stick” is one type of pointing device used, for example, with desktop and notebook computers. A pointing stick is a small analog joystick, usually disposed between the keys of a keyboard, which the user can manipulate to provide input to the electronic device. In some electronic devices (e.g., notebook computers), a pointing stick can be provided as an input option alongside a touchpad. 
     SUMMARY 
     Embodiments generally provide an input device, a processing system, and method to control a user interface indicator of an electronic device. In an embodiment, an isometric input device configured to control a user interface indicator of an electronic device includes a plurality of sensor electrodes disposed on a sensor substrate. The input device further includes a control member mechanically coupled to the sensor substrate over at least a portion of the plurality of sensor electrodes. The input device further includes a conductive support substrate and a compliant member disposed between the sensor substrate and the conductive support substrate. The input device further includes a securing component extending through the conductive support substrate and the compliant member and engaging with the control member, the securing component defining a gap between the sensor substrate and the conductive support substrate. 
     In another embodiment, a processing system for an input device configured to control a user interface indicator of an electronic device includes a sensor module and a determination module. The sensor module includes sensor circuitry, the sensor module configured to operate a plurality of sensor electrodes on a sensor substrate mechanically coupled to a control member by driving a sensing signal on a first subset of the plurality of electrodes and receiving resulting signals from a second subset of the plurality of electrodes, the resulting signals including effects from a change in spacing between the sensor substrate and a conductive support substrate caused by a deflection of the control member. The determination module is configured to measure a change in capacitive coupling between at least one ohmically isolated conductive element and the conductive support substrate based on the resulting signals, the at least one ohmically isolated conductive element disposed between the plurality of sensor electrodes and the conductive support substrate. 
     In another embodiment, a method of operating an input device configured to control a user interface indicator of an electronic device includes operating a plurality of sensor electrodes on a sensor substrate mechanically coupled to a control member by driving a sensing signal on a first subset of the plurality of electrodes and receiving resulting signals from a second subset of the plurality of electrodes, the resulting signals including effects from a change in spacing between the sensor substrate and a conductive support substrate caused by a deflection of the control member. The method further includes measuring a change in capacitive coupling between at least one ohmically isolated conductive element and the conductive support substrate based on the resulting signals, the at least one ohmically isolated conductive element disposed between the plurality of sensor electrodes and the conductive support substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of embodiments can be understood in detail, a more particular description of embodiments, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments and are therefore not to be considered limiting of scope, for other equally effective embodiments may be admitted. 
         FIG. 1  is a block diagram of a system that includes an input device according to an example implementation. 
         FIG. 2  is an exploded view of an input device in accordance with embodiments. 
         FIG. 3  is a cross-sectional side view of the input device of  FIG. 2  in accordance with embodiments. 
         FIG. 4  is an isometric view of the input device of  FIG. 2  in accordance with embodiments. 
         FIG. 5  is a cross-sectional side view of the input device of  FIG. 2  according to another embodiment. 
         FIG. 6  is a simplified cross-sectional side view of the input device of  FIG. 2  where a force is applied to a control member. 
         FIG. 7  is a schematic view of sensor electrodes on a substrate according to an embodiment. 
         FIG. 8  is embodiment cross-sectional side view showing an embodiment of a sensor substrate. 
         FIG. 9  is a block diagram of an input device according to an example implementation. 
         FIG. 10  is a flow diagram depicting a method of operating an input device configured to control a user interface indicator of an electronic device according to an embodiment. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements of one embodiment may be beneficially incorporated in other embodiments. 
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the embodiments or the application and uses of such embodiments. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
     Turning now to the figures,  FIG. 1  is a block diagram of an exemplary input device  100  in accordance with embodiments. In various embodiments, the input device  100  comprises one or more sensing devices, each of which can be integrated in, or coupled to, an electronic device  160 . As used in this document, the term “electronic system” (or “electronic device”) broadly refers to any system capable of electronically processing information. Some non-limiting examples of electronic systems include personal computers of all sizes and shapes, such as desktop computers, laptop computers, netbook computers, tablets, web browsers, e-book readers, and personal digital assistants (PDAs). Additional example electronic systems include composite input devices, such as physical keyboards that include input device  100  and separate joysticks or key switches. Further example electronic systems include peripherals such as data input devices (including remote controls and mice) and data output devices (including display screens and printers). Other examples include remote terminals, kiosks, and video game machines (e.g., video game consoles, portable gaming devices, and the like). Other examples include communication devices (including cellular phones, such as smart phones), and media devices (including recorders, editors, and players such as televisions, set-top boxes, music players, digital photo frames, and digital cameras). Additionally, the electronic system could be a host or a slave to the input device. 
     The input device  100  can be implemented as a physical part of the electronic system or can be physically separate from the electronic system. As appropriate, the input device  100  may communicate with parts of the electronic system using any one or more of the following: buses, networks, and other wired or wireless interconnections (including serial and or parallel connections). Examples include I 2 C, SPI, PS/2, Universal Serial Bus (USB), Bluetooth, RF, and IRDA. 
     In the embodiment depicted in  FIG. 1 , the input device  100  includes one or more input devices, such as a pointing stick  180  and a proximity sensor device  150  (also often referred to as a “touchpad” or a “touch sensor device”), each of which is configured to sense input provided by input object(s)  140  (illustratively shown as a user&#39;s finger). Proximity sensor device  150  is configured to sense input object(s)  140  in a sensing region  120 . The pointing stick  180  is configured to sense input object(s)  140  in a sensing region  190 . In an embodiment, the pointing stick  180  is disposed within or alongside another device  170 , such as a keyboard (e.g., the pointing stick  180  can be disposed between keys of a keyboard). Alternatively, the pointing stick  180  can be a “stand-alone” device separate and apart from any other input device. In some embodiments, the proximity sensor device  150  can be integrated into a display device (not shown) (e.g., a touch screen). In other embodiments, the proximity sensor device  150  can be a stand-alone device (e.g., a touchpad). In some embodiments, the proximity sensor device  150  is omitted. 
     Sensing regions  120 ,  190  encompass any space above, around, in, and/or near the input device  100  in which the input device  100  is able to detect user input (e.g., user input provided by input object(s)  140 ). The sizes, shapes, and locations of particular sensing regions may vary widely from embodiment to embodiment. In some embodiments, the sensing regions  120 ,  190  extend from a surface of the input device  100  in one or more directions into space until signal-to-noise ratios prevent sufficiently accurate object detection. The distance to which the sensing regions  120 ,  190  extend in a particular direction, in various embodiments, may be on the order of less than a millimeter, millimeters, centimeters, or more, and may vary significantly with the type of sensing technology used and the accuracy desired. Thus, in some embodiments, the proximity sensor device  150  and the pointing stick  180  sense input that comprises no contact with any surfaces of the input device  100 , contact with an input surface (e.g., a touch surface) of the input device  100 , contact with an input surface of the input device  100  coupled with some amount of applied force or pressure, and/or a combination thereof. 
     The input device  100  may utilize any combination of sensor components and sensing technologies to detect user input in the sensing regions  120 ,  190 . The input device  100  comprises one or more sensing elements for detecting user input. Cursors, menus, lists, items, and other user interface indicators may be displayed as part of a graphical user interface and may be scaled, positioned, selected scrolled, or moved in response to sensed user input. 
     In some capacitive implementations of the input device  100 , voltage or current is applied to create an electric field. Nearby input objects cause changes in the electric field and produce detectable changes in capacitive coupling that may be detected as changes in voltage, current, or the like. 
     Some capacitive implementations utilize arrays or other regular or irregular patterns of capacitive sensing elements, such as sensor electrodes, to create electric fields. In some capacitive implementations, separate sensing elements may be ohmically shorted together to form larger sensor electrodes. Some capacitive implementations utilize resistive sheets (e.g., may comprise a resistive material such as ITO or the like), which may be uniformly resistive. 
     Some capacitive implementations utilize “self capacitance” (or “absolute capacitance”) sensing methods based on changes in the capacitive coupling between sensor electrodes and an input object. In various embodiments, an input object near the sensor electrodes alters the electric field near the sensor electrodes, changing the measured capacitive coupling. In one implementation, an absolute capacitance sensing method operates by modulating sensor electrodes with respect to a reference voltage (e.g., system ground) and by detecting the capacitive coupling between the sensor electrodes and input objects. 
     Some capacitive implementations utilize “mutual capacitance” (or “transcapacitance”) sensing methods based on changes in the capacitive coupling between sensor electrodes. In various embodiments, an input object near the sensor electrodes alters the electric field between the sensor electrodes, changing the measured capacitive coupling. In one implementation, a transcapacitive sensing method operates by detecting the capacitive coupling between one or more transmitter sensor electrodes (also “transmitter electrodes” or “transmitters”) and one or more receiver sensor electrodes (also “receiver electrodes” or “receivers”). Transmitter sensor electrodes may be modulated relative to a reference voltage (e.g., system ground) to transmit transmitter signals. Receiver sensor electrodes may be held substantially constant relative to the reference voltage to facilitate receipt of resulting signals. A resulting signal may comprise effect(s) corresponding to one or more transmitter signals and/or to one or more sources of environmental interference (e.g., other electromagnetic signals). Sensor electrodes may be dedicated transmitters or receivers, or sensor electrodes may be configured to both transmit and receive. Alternatively, the receiver electrodes may be modulated relative to ground. 
     In  FIG. 1 , a processing system  110  is shown as part of the input device  100 . The processing system  110  is configured to operate the hardware of the input device  100  to detect input in the sensing regions  120 ,  190 . The proximity sensor device  150  and the pointing stick  180  generally include an array of sensing elements. The processing system  110  comprises parts of, or all of, one or more integrated circuits (ICs) and/or other circuitry components. For example, a processing system for a mutual capacitance sensor device may comprise transmitter circuitry configured to transmit signals with transmitter sensor electrodes and/or receiver circuitry configured to receive signals with receiver sensor electrodes. In some embodiments, the processing system  110  also comprises electronically-readable instructions, such as firmware code, software code, and/or the like. In some embodiments, components of the processing system  110  are located together, such as near sensing element(s) of the input device  100 . In other embodiments, components of processing system  110  are physically separate with one or more components close to sensing element(s) of input device  100  and one or more components elsewhere. For example, the input device  100  may be a peripheral coupled to a desktop computer, and the processing system  110  may include software configured to run on a central processing unit of the desktop computer and one or more ICs (perhaps with associated firmware) separate from the central processing unit. As another example, the input device  100  may be physically integrated in an electronic device, and the processing system  110  may comprise circuits and firmware that are part of a main processor of the electronic device (e.g., a notebook computer). In some embodiments, the processing system  110  is dedicated to implementing the input device  100 . In other embodiments, the processing system  110  also performs other functions, such as operating display screens, driving haptic actuators, etc. 
     The processing system  110  may be implemented as a set of modules that handle different functions of the processing system  110 . Each module may comprise circuitry that is a part of the processing system  110 , firmware, software, or a combination thereof. In various embodiments, different combinations of modules may be used. Example modules include hardware operation modules for operating hardware such as sensor electrodes and display screens, data processing modules for processing data such as sensor signals and positional information, and reporting modules for reporting information. Further example modules include sensor operation modules configured to operate sensing element(s) to detect input, identification modules configured to identify gestures such as mode changing gestures, and mode changing modules for changing operation modes. 
     In some embodiments, the processing system  110  responds to user input (or lack of user input) in the sensing regions  120 ,  190  directly by causing one or more actions. Example actions include changing operation modes, as well as GUI actions such as cursor movement, selection, menu navigation, and other functions. In some embodiments, the processing system  110  provides information about the input (or lack of input) to some part of the electronic system (e.g., to a central processing system of the electronic system that is separate from the processing system  110 , if such a separate central processing system exists). In some embodiments, some part of the electronic system processes information received from the processing system  110  to act on user input, such as to facilitate a full range of actions, including mode changing actions and GUI actions. 
     For example, in some embodiments, the processing system  110  operates sensing element(s) of the input device  100  to produce electrical signals indicative of input (or lack of input) in the sensing regions  120 ,  190 . The processing system  110  may perform any appropriate amount of processing on the electrical signals in producing the information provided to the electronic system. For example, the processing system  110  may digitize analog electrical signals obtained from the sensor electrodes. As another example, the processing system  110  may perform filtering or other signal conditioning. As yet another example, the processing system  110  may subtract or otherwise account for a baseline, such that the information reflects a difference between the electrical signals and the baseline. As yet further examples, the processing system  110  may determine positional information, recognize inputs as commands, recognize handwriting, and the like. 
     “Positional information” as used herein broadly encompasses absolute position, relative position, velocity, acceleration, and other types of spatial information. Exemplary “zero-dimensional” positional information includes near/far or contact/no contact information. Exemplary “one-dimensional” positional information includes positions along an axis. Exemplary “two-dimensional” positional information includes motions in a plane. Exemplary “three-dimensional” positional information includes instantaneous or average velocities in space. Further examples include other representations of spatial information. Historical data regarding one or more types of positional information may also be determined and/or stored, including, for example, historical data that tracks position, motion, or instantaneous velocity over time. 
     In some embodiments, the input device  100  is implemented with additional input components that are operated by the processing system  110  or by some other processing system. These additional input components may provide redundant functionality for input in the sensing region  120  or some other functionality.  FIG. 1  shows buttons  130  near the sensing region  120  that can be used to facilitate selection of items using the input device  100 . Other types of additional input components include sliders, balls, wheels, switches, and the like. Conversely, in some embodiments, the input device  100  may be implemented with no other input components. 
     It should be understood that while many embodiments are described in the context of a fully functioning apparatus, the mechanisms of the embodiments are capable of being distributed as a program product (e.g., software) in a variety of forms. For example, the mechanisms of the present invention may be implemented and distributed as a software program on information bearing media that are readable by electronic processors (e.g., non-transitory computer-readable and/or recordable/writable information bearing media readable by the processing system  110 ). Additionally, the embodiments of the present invention apply equally regardless of the particular type of medium used to carry out the distribution. Examples of non-transitory, electronically readable media include various discs, memory sticks, memory cards, memory modules, and the like. Electronically readable media may be based on flash, optical, magnetic, holographic, or any other storage technology. 
       FIG. 2  is an exploded view of an input device  200  in accordance with embodiments.  FIG. 3  is a cross-sectional side view of the input device  200  in accordance with embodiments.  FIG. 4  is an isometric view of the input device  200  in accordance with embodiments. Referring to  FIGS. 2-4 , the input device  200  can be used as an embodiment of the pointing stick  180  shown in  FIG. 1  to control a user interface indicator of an electronic device. The input device  200  includes a control member  202 , a compliant member  204 , a substrate  206  (also referred to as a sensor substrate), and a conductive support substrate  208 . The sensor substrate  206  includes sensor electrodes  207  disposed thereon. The sensor substrate  206  can include one or more conductive layers (not shown) separated by one or more dielectric layers (not shown). For example, the sensor substrate  206  can be a printed circuit board (PCB), flexible printed circuit (FPC), or the like. In the present example, the sensor substrate  206  has an annular shape having an aperture  210  in the center thereof. In other examples, the sensor substrate  206  can have a different shape generally having an aperture. The sensor electrodes  207  on the sensor substrate  206  can be coupled to conductive traces (not shown) on a connection medium  212 , such as an FPC, ribbon cable, or the like, which can be used to drive signals to, and receive signals from, the sensor electrodes  207 . The connection medium  212  communicatively couples the input device  200  to the processing system  110 . In an embodiment, the processing system  110  is also coupled to a capacitive touch pad of the electronic device. 
     In an embodiment, the sensor electrodes  207  can be formed using multiple layers of the sensor substrate  206 . In other examples, the sensor electrodes  207  can be formed on a single layer of the sensor substrate  206 . In an embodiment, at least two layers of the sensor electrodes  207  can be provided. The sensor electrodes  207  in a first layer can be used to detect motion of the pointing stick  180  as described herein. The sensor electrodes  207  in a second layer can be used to detect input proximate the pointing stick  180  using capacitive touch sensing techniques (e.g., absolute sensing or transcapacitive sensing, as described above). For example, the sensor electrodes  207  on the second layer can be used to detect the presence of an input object, gestures performed by an input object, or the like associated with capacitive touch sensing. The second layer can be disposed on top of the first layer (e.g., more proximate the control member  202 ). Alternatively, the second set of sensor electrodes  207  can be formed on an additional substrate, which can be adhered to the sensor substrate  206  or adhered to the control member  202 . Thus, the sensor electrodes  207  can be configured to detect motion of the pointing stick  180 , or both motion of the pointing stick  180  and input proximate the pointing stick  180  (e.g., a finger touching the pointing stick  180  or proximate the pointing stick  180 ). 
     The control member  202  is mechanically coupled to the sensor substrate  206 . In an embodiment, the control member  202  includes a base  214 , an adapter  216  extending upwards from a top surface  220  of the base  214 , and a bore  217 . The base  214  and the adapter  216  are cylindrical in shape. The bore  217  extends from a bottom surface  222  of the base  214  and into the adapter  216 . The control member  202  can comprise, for example, a single plastic element that is molded, printed, or the like using known techniques. The bore  217  is configured to engage with an insert  260 . The insert  260  can include a bore  262  configured to engage with a securing component  250 . The insert  260  can comprises, for example, metal. The insert  260  can be press fit, ultrasonically welded, or the like within the control member  202 . In an embodiment, the bore  262  includes a threaded surface configured to engage a threaded surface of the securing component  250 . In another embodiment, the bore  262  can have a diameter smaller than the diameter of the securing component  250 , and the securing component  250  can be press fit into the control member  202 . 
     In an embodiment, the securing component  250  comprises a head  252  and a post  256 . The securing component  250  can be formed of metal (e.g., brass). The post  256  is generally cylindrical in shape and includes a first portion  256 A that is larger in circumference than a second portion  256 B. The post  256  extends through an aperture  228  of the conductive support substrate  208 , an aperture  230  of the compliant member  204 , through the aperture  210  of the sensor substrate  206 , and into the bore  262  of the control member  202 . In an embodiment, the second portion  256 B of the post  256  comprises a threaded surface mechanically coupled to a threaded surface of the bore  262 . In another embodiment, the second portion  256 B of the post  256  comprises a surface that engages with a surface of the bore  262  through friction (e.g., press fit). 
     The first portion  256 A of the post  256  comprises a “step” the height of which controls a gap  232  between the sensor substrate  206  and the conductive support substrate  208 . In particular, the height of the first portion  256 A of the post  256  extends between the head  252  and the bottom surface  222  of the control member  202 . The first portion  256 A of the post  256  pass through the aperture  228  of the conductive support substrate  208  and the aperture  230  of the compliant member  204 . The gate  232  between the sensor substrate  206  and the conductive support substrate  208  can be increased or decreased by respectively increasing or decreasing the height of the first portion  256 A of the post  256 . 
     The sensor substrate  206  can be adhered to the bottom surface  222  of the base  214  using an adhesive. The bottom surface  222  of the base  214  extends over the sensor electrodes  207 . In general, the bottom surface  222  of the base  214  extends over at least a portion of the sensor electrodes  207 . The input device  200  can include an optional cap  224  mounted to the adapter  216 . The cap  224  can provide an input surface for a user&#39;s finger. The cap  224  can be fixedly mounted to the adapter  216  using, for example, an adhesive. Alternatively, the cap  224  can be removably mounted to the adapter  216  (e.g., held in place through friction). The cap  224  can comprise a semi-rigid material, such as plastic, or a compliant material, such as an elastomer. 
     The control member  202  shown in  FIGS. 2-4  is just one example control member that can be used in the input device  200 . The shapes of the base  214  and the adapter  216  can differ from that shown. In some examples, the cap  224  can be omitted and the adapter  216  can be shaped as a nub or other protuberance that provides an input surface for a user&#39;s finger. 
     The conductive support substrate  208  is mounted to a substrate (not shown) of the electronic device in which the input device  200  is mounted, such as a keyboard plate. Through mounting, the conductive substrate  208  is ohmically coupled to a substantially constant electrical potential, such as an electrical ground. The sensor electrodes  207  are capacitively coupled to the conductive support substrate  208 . The conductive support substrate  208  can include one or more mounting holes  226  (e.g., three are shown). The conductive support substrate  208  can be mounted to the electronic device using fasteners (not shown) passing through the mounting holes  226 . The conductive support substrate  208  also includes an aperture  228  through which the securing component  250  extends. The conductive support substrate  208  can comprise metal or other conductive material. The conductive support substrate  208  can have any of a myriad of shapes, depending on how the input device  200  is to be mounted to the electronic device. The conductive support substrate  208  is not limited to any particular shape, including the shape shown in  FIGS. 2-4 . 
     The compliant member  204  is disposed between the base  214  of the control member  202  and the conductive support substrate  208 . The compliant member  204  can comprise a compliant material, such as an elastomeric material (e.g., silicone rubber). The compliant member  204  has a cylindrical shape and includes the aperture  230  through which the securing component  250  extends. For example, the compliant member  204  can comprise an elastomeric washer or the like. In other examples, the compliant member  204  can have a different shape generally having an aperture that allows the securing component  250  to pass through the compliant member  204 . The compliant member  204  contacts the bottom surface  222  of the base  214  at one end, and the conductive support substrate  208  at the other end. The compliant member  204  passes through the aperture  210  of the sensor substrate  206 . The thickness of the compliant member  204  can be such that the compliant member  204  contacts both the conductive support substrate  208  and the bottom surface  222  of the control member  202 . 
     In the present example, the control member  202  includes a plurality of alignment features  280  extending from the bottom surface thereof. The alignment features  280  engage a plurality of alignment receiving features  282  in the conductive support substrate  208 . The alignment receiving features  282  restrict planar translation and rotation of the control member  202  with respect to the conductive support substrate. In another embodiment, the alignment features  280  and the alignment receiving features  282  can be omitted. 
       FIG. 5  is a cross-sectional side view of the input device  200  in accordance with another embodiment. Elements in  FIG. 5  that are the same or similar to those shown in  FIGS. 2-4  are designated with identical reference numerals. In the present example, the control member  202  can comprise, for example, metal (e.g., brass, aluminum, etc.) that has been cast, machined, or the like, or a combination thereof, to form a single metal component. The insert  260  is omitted, and the bore  262  is formed directly in the control member  202 . The bore  262  is configured to engage with the securing component  250 , as described in embodiments above. 
       FIG. 6  is a simplified cross-sectional side view of the input device  200  where a force is applied to the control member  202 . Some reference characters shown in  FIGS. 2-5  are omitted for clarity. In the present example, a force is applied to the control member  202 . The force is applied proximate an edge of the control member  202  such that the control member rotates about a pivot  219 . Due to the rotation, one portion of the sensor substrate  206  is disposed nearer to the conductive support substrate  208 , and another portion of the sensor substrate  206  is disposed farther from the conductive support substrate  208 . Thus, a gap  232 A beneath the edge of the control member  202  having the applied force is narrower than a gap  232 B beneath the opposite edge of the control member  202 . As the force is applied, some of the electrodes  207  on the substrate  206  are brought nearer to the conductive support substrate  208 , while others of the electrodes  207  are brought farther from the conductive support substrate  208 . The compliant member  204  provides a biasing force opposite the force applied to the control member  202 . When the force applied to the control member  202  is removed, the compliant member  204  provides a restoring force that causes the control member  202  to return to its initial state as shown in  FIG. 3  or  FIG. 5 . In general, by applying force to the control member  202 , some of the sensor electrodes  207  are brought closer to the conductive support substrate  208 , while others of the sensor electrodes  207  are brought farther from the conductive substrate  208 . The sensor electrodes  207  return to their initial position when the force is removed from the control member  202 . 
       FIG. 7  is a schematic view of the sensor electrodes  207  on the substrate  206  according to an embodiment. The substrate  202  includes a sensor electrode area  702  forming a sensing region for the input device  200 . The sensor electrode area  702  can be divided into quadrants designated y−, x−, y+, and x+. The sensor electrodes  207  are disposed on the substrate  202  such that unique sensor electrode patterns  704 - 1 ,  704 - 2 ,  704 - 3 , and  704 - 4  are disposed in the quadrants y−, x−, y+, and x+. A center  713  of the sensor electrode area  702  is substantially aligned with a center of the aperture  210  in the substrate  206  and the center of the control member  202 . 
     In operation, the conductive support substrate  208  is held at a substantially constant voltage, such as electrical ground. In an example, the processing system  110  drives one or more of the sensor electrodes  207  with a transmitter signal and receives resulting signals from others of the sensor electrodes  207 . The processing system  110  can determine measurements of transcapacitance from the resulting signals. The processing system  110  can establish baseline measurements of transcapacitance absent force applied to the control member  202 . When a force is applied to the control member  202 , at least one of the electrode patterns  704  is disposed nearer the conductive support substrate  208 , and at least one of the electrode patterns  704  is disposed farther from the conductive support substrate  208 . The transcapacitance measurements derived from those electrode patterns  704  that are disposed nearer and farther from the conductive support substrate  208  change from the baseline. In other examples, the processing system  110  can measure absolute capacitance derived from the electrode patterns  704 . The absolute capacitance measurements change from a baseline as electrode pattern(s)  704  are brought nearer and farther from the conductive support substrate  208 . In general, a force applied to the control member  202  results in a change in the gap  232  between the substrate  206  and the conductive support substrate  208 , which changes a variable capacitance between at least one of the sensor electrodes  207  and the conductive support substrate  208 . 
     For example, a force can be applied to the control member  202  such that the sensor electrode pattern  704 - 2  is brought nearer the conductive support substrate  208 . Consequently, the sensor electrode pattern  704 - 4  is brought farther from the conductive support substrate  208 . The processing system  110  detects changes in transcapacitance measurements associated with the sensor electrode patterns  704 - 2  and  704 - 4 . In this manner, the processing system  110  can determine that the applied force is aligned with the x− quadrant. In another example, a force can be applied to the control member  202  such that the sensor electrode patterns  704 - 1  and  704 - 2  are brought nearer the conductive support substrate  208 , and the sensor electrode patterns  704 - 3  and  704 - 4  are brought farther from the conductive support substrate  208 . The processing system  110  detects changes in transcapacitance measurements from each of the sensor electrode patterns  704 . In this manner, the processing system  110  can determine that the applied force is aligned between the x− and y− quadrants. By detecting force alignment, the processing system  110  can determine motion of a user interface indicator, such as a cursor. 
       FIG. 8  is a cross-sectional side view showing an embodiment of the sensor substrate  206 . As shown, the sensor substrate  206  is disposed above the conductive support substrate  208  and separated from the conductive support substrate  208  by the gap  232 . As noted above, the gap  232  can be dynamically increased or decreased by applying force to the input device  200 . The sensor substrate  206  includes a dielectric layer  802 , transmitter electrodes  207 T, receiver electrodes  207 R (only one is shown in the example), a dielectric layer  804 , a floating electrode  806 , and a dielectric layer  808 . The transmitter electrodes  207 T and the receiver electrodes  207 R are disposed between the dielectric layers  802  and  804 . The floating electrode  806  is disposed between the dielectric layers  804  and  808 . The dielectric layer  802  is adhered to the control member  202  (not shown in  FIG. 8 ). The dielectric layer  808  faces the conductive support substrate  208 . 
     The floating electrode  806  is not coupled to any potential and is left electrically floating. By “electrically floating”, it is meant that there is no significant ohmic contact between the floating electrode and other circuit elements of the input device, so that no meaningful amount of charge can flow onto or off of the floating electrode under normal circumstances. Of course, any charge present on the conductive floating electrode can still redistribute itself in the presence of an electric field. Thus, the floating electrode  806  is capacitively coupled to the transmitter electrodes  207 T and the receiver electrodes  207 R, but it is not ohmically coupled significantly to those or other circuit elements, and it does not require any wiring or other forms of electrical connection to other circuit elements. 
     In operation, the processing system  110  couples transmitter signals to the transmitter electrodes  207 T, and receives resulting signals from the receiver electrodes  208 R. The transmitter electrodes  207 T are capacitively coupled to the receiver electrodes  207 R and to the floating electrode  806 . The receiver electrodes  207 R are also capacitively coupled to the floating electrode  806 . Notably, the capacitance between the transmitter electrodes  207 T and the floating electrode  806  (Ct), and the capacitance between the receiver electrodes  207 R and the floating electrode  806  (Cr), are fixed capacitances. The floating electrode  806  is capacitively coupled to the conductive support substrate  208 . Since the gap  232  is variable and subject to change in response to force applied to the input device  200 , the capacitance between the floating electrode  806  and the conductive support substrate  208  (Cx) is variable and dependent on the applied force. The baseline capacitance of the sensor substrate  206  is a combination of the capacitances Ct, Cr, and Cx, and is variable depending on the gap  232  and hence the force applied to the input device  200 . By measuring changes in the baseline capacitance Cb, the processing system  110  can measure force applied to the input device  200 . 
       FIG. 9  is a block diagram of an input device  900  according to an example implementation. The input device  900  comprises an example implementation of the input device  100  shown in  FIG. 1 . The input device  900  includes the pointing stick  180  coupled to the processing system  110 . The pointing stick  180  can include the input device  200  described above. Accordingly, the pointing stick  180  includes the sensor electrodes  207 . In some embodiments, the processing system  110  is further coupled to a two-dimensional capacitive input device, such as the proximity sensor device  150 . The proximity sensor device  150  can include a two-dimensional array of sensor electrodes  980  that can be used for capacitive sensing of input. Thus, the processing system  110  can drive sensor electrodes of the pointing stick  180  or, in some embodiments, sensor electrodes of both the pointing stick  180  and the proximity sensor device  150 . 
     In general, the processing system  110  drives sensor electrodes, receives from sensor electrodes, or both to measure changes in variable capacitance (e.g., transcapacitance or absolute capacitance). The terms “excite” and “drive” as used herein encompasses controlling some electrical aspect of the driven element. For example, it is possible to drive current through a wire, drive charge into a conductor, drive a substantially constant or varying voltage waveform onto an electrode, etc. The processing system  110  can drive a sensor electrode with a transmitter signal. A transmitter signal can be constant, substantially constant, or varying over time, and generally includes a shape, frequency, amplitude, and phase. The processing system  110  can receive a resulting signal from a sensor electrode. The resulting signal can include effects of an input object. The processing system  110  can determine measurements of transcapacitance or absolute capacitance from a resulting signal. 
     The processing system  110  can include a sensor module  940  and a position determiner module  960 . The sensor module  940  and the position determiner module  960  comprise modules that perform different functions of the processing system  110 . In other examples, different configurations of modules can perform the functions described herein. The sensor module  940  and the position determiner module  960  can be implemented using sensor circuitry  975  and can also include firmware, software, or a combination thereof operating in cooperation with the sensor circuitry  975 . 
     The sensor module  940  is configured to operate the sensor electrodes  207 . As described above, the sensor electrodes  207  are disposed on a substrate  206  that is mechanically coupled to the control member  202 . The sensor module  940  is configured to drive a sensing signal on a first subset of the sensor electrodes  207  and receive resulting signals from a second subset of the sensor electrodes  207 . For example, as shown in  FIG. 8 , the sensor module  940  can drive the transmitter electrode  207 T with a sensing signal and receive resulting signals from the receiver electrodes  207 R. The resulting signals include effects from a change in baseline capacitance, which changes in response to a change in spacing between the substrate  206  and the conductive support substrate  208  caused by a deflection of the control member  202 . While the sensor module  940  is operating the sensor electrodes  207 , the sensor module  940  can also operate the sensor electrodes  980 . 
     In an embodiment, the determination module  960  is configured to measure a change in capacitive coupling between the sensor electrodes  207  and the floating electrode  806 , as well as a change in baseline capacitance, based on the resulting signals. If the sensor substrate  206  does not include a floating electrode  806 , the determination module  960  can measure a change in capacitive coupling between the sensor electrodes  207  and the conductive support substrate  208  based on the resulting signals. The determination module  960  can control a user interface indicator in response to a change in capacitive coupling. The user interface indicator can comprise, for example, a cursor of an electronic device. The determination module  960  can control motion of the cursor in response to changes in capacitive couplings and/or baseline capacitance. 
       FIG. 10  is a flow diagram depicting a method  1000  of operating an input device configured to control a user interface indicator of an electronic device according to an embodiment. The method  1000  begins at step  1002 , where the processing system  110  operates a plurality of sensor electrodes  207  on a sensor substrate  206  mechanically coupled to a control member  202  by driving a sensing signal on a first subset of the sensor electrodes  207  and receiving resulting signals on a second subset of the sensor electrodes  207 . At step  1004 , the processing system  110  measures changes in capacitive coupling between at least one ohmically isolated conductive element (e.g., the floating electrode  806 ) and the conductive support substrate  208  based on the resulting signals. At step  1006 , the processing system  110  can control a user interface indicator in response to changes in the capacitive coupling. 
     Thus, the embodiments and examples set forth herein were presented in order to best explain the present invention and its particular application and to thereby enable those skilled in the art to make and use the invention. However, those skilled in the art will recognize that the foregoing description and examples have been presented for the purposes of illustration and example only. The description as set forth is not intended to be exhaustive or to limit the invention to the precise form disclosed.