Stylus hover and positioning communication protocol

Abstract

Hover and position communication protocols for a stylus are described. A touch sensitive device includes a capacitive-based touch sensor, drive circuitry configured to drive touch sensor electrodes with a synchronization waveform to time synchronize an active stylus with the touch sensitive device, and receive circuitry configured to determine a position of the active stylus based on electrostatically receiving a first waveform from the active stylus. Depending on when the touch sensitive device receives the first waveform from the active stylus, the touch sensitive device interprets the first waveform differently to determine a position of the active stylus or to determine that the active stylus is hovering. In either case, the same waveform is used to communicate different information about the active stylus to the touch sensitive device.

Description

[0001] This patent application is a continuation-in-part of International Application No. PCT / US2017 / 058918, International Filing Date October 30, 2017, entitled "Stylus Hover and Positioning Communication Protocol," which entered the U.S. National Stage as U.S. Patent Application No. 15 / 882, 1 19, filed January 30, 2018, which claims priority to U.S. Provisional Patent Application No. 62 / 569, 1 17, filed October 3, 2017. TECHNICAL FIELD

[0002] This invention relates to touch-sensitive devices. BACKGROUND

[0003] Many touch-sensitive computing devices employ active styluses to enhance touch interaction. Determination of the position of a stylus can be provided via electrostatic communication (i.e., between the stylus and a touch sensor of the host computing device) and other functionality is enabled in such systems. The host computing device and its various components (display, capacitive touch sensor, etc.) are sometimes referred to collectively herein as the "digital converter." BRIEF DESCRIPTION OF DRAWINGS

[0004] Figure 1 An example display device is shown that includes a touch sensor that receives touch input from a user's body and an active stylus.

[0005] Figure 2 An example touch-sensitive display device is shown.

[0006] Figure 3 An example in-cell touch sensor matrix is shown.

[0007] Figure 4 An example touch-sensing frame is shown that includes a plurality of full-search subframes.

[0008] Figure 5 Another example touch-sensing frame is shown that includes a plurality of full-search subframes and a plurality of partial-search subframes.

[0009] Figure 6 An example stylus communication frame is shown.

[0010] Figure 7 An example method of causing an active stylus to communicate information to a touch-sensitive device is shown.

[0011] Figure 8 AND 9 An example touch-sensing method for a touch-sensitive device is shown.

[0012] Figure 10 An example computing system is shown. DETAILED DESCRIPTION

[0013] As indicated above, many touch interactive computing devices employ active styluses to enhance functionality. Position sensing and other operations in these devices are typically achieved via electrostatic communication between the stylus and the digitizer. For example, a stylus can include one or more tip electrodes that interact with electrodes of a touch sensor incorporated within the digitizer (e.g., row / column or independent self-capacitance sensing points). When the stylus and digitizer are in close enough proximity, application of an excitation waveform on the stylus electrodes affects the electrical behavior at the digitizer (e.g., charge accumulation, capacitance, voltage / current on one or more touch sensor electrodes). Similarly, excitation of the digitizer electrodes affects conditions on the stylus electrodes.

[0014] Electrostatic interactions between the devices (e.g., electrode-to-electrode capacitive coupling) can be used for various purposes. For example, capacitive coupling can be used to: (1) send / receive synchronization signals to establish / maintain a shared sense of time between the stylus and the digitizer; (2) determine the position of the stylus relative to the digitizer, which can include using multiple electrodes to finely interpolate position; (3) communicate status / present conditions between the stylus and the digitizer, such as identifiers, stylus button status, battery level, etc.; and (4) transmit various other data, such as force determined in the stylus tip, firmware updates, encryption keys / information, times of various event occurrences, etc. These are just some non-limiting examples. Ultimately, the digitizer interacting with touch tools (fingers and stylus) is used to control the display output and either selectively control the digitizer.

[0015] In some cases, the waveforms transmitted by the stylus can interfere with touch sensing operations of the digitizer. For example, the stylus can electrostatically transmit a "report" waveform (e.g., indicating position, status, or other data) to the digitizer, and if the digitizer is not operating in the proper mode when the report waveform is received by the digitizer, the digitizer can incorrectly interpret the waveform as an active (e.g., finger) touch. Furthermore, if the digitizer correctly detects a real finger touch at the same time but in a different area of the digitizer, the digitizer can operate in a conflicting manner due to the two finger touches (i.e., the real finger touch and the false finger touch) occurring far apart from each other.

[0016] In one example, a digitizer includes receive circuitry configured to selectively multiplex to different portions of a touch sensor at different times to detect touches. The digitizer is configured to switch between 1) detecting coarse locations of stylus and finger touches and 2) detecting precise locations of a stylus and receiving other data from the stylus, such as touch force. The stylus can not know when the digitizer switches between these two operating states. As such, if the stylus transmits a reporting waveform to indicate touch force while the digitizer is detecting a finger touch, the digitizer will incorrectly interpret the received waveform as a finger touch and the digitizer will not receive the touch force information. Such interference reduces the touch sensing accuracy of the digitizer. Moreover, such interference reduces the robustness of the communication between the stylus and the digitizer.

[0017] In one example, the stylus can be made aware of the operating state of the digitizer in order to better synchronize with the digitizer by using a communication protocol that includes a bit to indicate the operating state of the digitizer. Specifically, this bit is transmitted by the digitizer during each touch sensing frame. However, using this bit will take up limited communication resources that could be used elsewhere due to the limited bandwidth of the electrostatic communication between the stylus and the digitizer.

[0018] Accordingly, the present disclosure relates to a method in which the same waveform is used to communicate the position of a stylus or the hovering state of a stylus to a touch sensitive device depending on when the waveform is received by the touch sensitive device. Specifically, when the waveform is received at a first time based on a time synchronization between the stylus and the touch sensitive device, the touch sensitive device determines the position of the stylus based on the waveform. In addition, when the waveform is received at a second time based on the time synchronization between the stylus and the touch sensitive device, the touch sensitive device determines that the stylus is hovering. By using the same "positioning" and "hovering" waveforms to communicate different types of information at different times, the stylus can communicate information in a way that does not interfere with the touch sensing operation of the touch sensitive device.

[0019] Furthermore, in implementations in which the touch sensitive device switches between two operating states, by using the same waveform to communicate information in both operating states, the stylus does not need to be aware of the operating state of the touch sensitive device to successfully transmit the appropriate information. In this way, a bit indicating the operating state of the touch sensitive device can be omitted from the touch sensing frames used by the touch sensitive device.

[0020] Figure 1A touch interactive display system 100 including a display device 102 having a touch sensor 104 is shown. In some examples, the display device 102 can be a large format display having a diagonal dimension D greater than 1 meter, although the display can take any suitable size. The display device 102 can be configured to sense one or more input sources, such as touch input imparted via a finger 106 and / or input provided by an input device 108 (shown in Figure 1 as a stylus) in contact with the display 102. The stylus 108 can be passive or active. An active stylus can include electrodes configured to transmit a waveform received by the touch sensor 104 to determine the location of the active stylus. The finger 106 and input device 108 are provided as non-limiting examples, and any other suitable input source can be used in conjunction with the display device 102. The display device 102 can be configured to receive input from styluses and fingers that are in contact with and / or "hovering" over the display surface of the display 102. As used herein, "touch input" refers to both finger and non-finger (e.g., stylus) input, as well as input provided by an input device that is both in contact with the display device 102 and spaced apart from but proximate to the display device 102. In some examples, the display device 102 can be configured to receive input from two or more sources simultaneously, in which case the display can be referred to as a multi-touch display.

[0021] The display device 102 can be operatively coupled to an image source 110, which can be, for example, a computing device external to the display or housed within the display. The image source 110 can receive input from the display device 102, process the input, and generate appropriate graphical output 112 for the display in response. In this way, the display device 102 can provide a natural paradigm for interacting with a computing device that can appropriately respond to touch input. Details regarding example computing devices are described below with reference to Figure 10 FIG. 4.

[0022] Figure 2 An example touch sensitive display device 200 is shown, which includes a display 202 and a touch sensor 204 that respectively implement outputting graphical content and receiving input. The display 202 can be operable to emit light in an upward direction through the display device 200 such that a perceivable image can be formed at a top surface 206 of the display device or other apparent location. For example, the display 202 can take the form of a liquid crystal display (LCD), an organic light emitting diode display (OLED), or any other suitable display. To implement display operations, Figure 2A display 202 is shown operatively coupled to a controller 208, which can control pixel operation, refresh rate, driving electronics, operation of a backlight (if any), and / or other aspects of the display. A suitable image source, which can be integrated with or separate from the controller 208, can provide graphical content for output by the display 202. The image source can be a computing device external to or integrated within the display system 200, for example.

[0023] The touch sensor 204 is operable to receive input, which can take various suitable forms. As examples, the touch sensor 204 can detect: (1) a touch input applied by a human finger 210 in contact with a top surface 206 of the display device 200; (2) a force and / or pressure applied by the finger 210 to the top surface 206; (3) a hover input applied by the finger 210 proximate to the top surface 206 but not in contact with the top surface 206; (4) a height of the hovering finger 210 from the top surface 206 such that a substantially continuous range of heights from the top surface 206 can be determined; and / or (5) input from a non-finger touch source such as an active stylus 212. As described in further detail below, the touch sensor 204 can receive position, tip force, button state, and / or other information from the stylus 212, and in some examples can transmit information to the stylus. The touch sensor 204 is operable to receive input from multiple input sources (e.g., fingers, stylus, other input devices) simultaneously, in which case the display device can be referred to as a "multi-touch" display device. To enable input reception, the touch sensor 204 can be configured to detect changes associated with capacitance of multiple electrodes of the touch sensor 204, as described in further detail below.

[0024] Touch input (and / or other information) received by the touch sensor 204 is operable to affect any suitable aspect of the display 202 and / or a computing device operatively coupled to the display device 200, and can include two-dimensional or three-dimensional finger input and / or gestures. As examples, Figure 2 The output of the display 202 is depicted in correspondence with a path space depicted by the finger 210 and stylus 212 proximate to the top surface 206. Although Figure 2 The controller 208 is shown as affecting operation of both the display 202 and the touch sensor 204 (e.g., electrode driving / receiving operation), but separate display and touch sensor controllers can be provided.

[0025] Display device 200 can be implemented in various forms. For example, display device 200 can be implemented as a so-called "large-format" display device having a diagonal dimension of approximately one meter or more, or in a mobile device (e.g., tablet, smartphone) having a diagonal dimension on the order of inches. Other suitable forms are contemplated, including but not limited to desktop display monitors, high-definition television screens, tablet devices, laptop computers, etc.

[0026] In addition to display 202 and touch sensor 204, display device 200 can include other components. As an example, Figure 2 A touch sheet 214 is shown that includes an optically transparent touch sheet 214 that provides a top surface 206 for receiving touch input as described above. Touch sheet 214 can be composed of any suitable material, such as glass or plastic. In addition, an optically clear adhesive (OCA) 216 adheres a bottom surface of touch sheet 214 to a top surface of display 202. As used herein, "optically clear adhesive" refers to a class of adhesives that transmit substantially all (e.g., about 99%) of incident visible light. Alternatively additionally, display device 200 can include any suitable components not shown in FIG. 2, including but not limited to various optical elements (e.g., lenses, diffusers, diffractive optical elements, waveguides, filters, polarizers). Figure 2 In addition to display 202 and touch sensor 204, display device 200 can include other components. As an example,

[0027] Figure 2 Integration of touch sensor 204 within display 202 in a so-called "in-cell" touch sensor implementation is depicted. In this example, one or more components of display device 200 are operable to perform both display output and input sensing functions. As a particular example, the same physical electrical structure can be used for both capacitive sensing and for determining the field in liquid crystal material that is used to determine the rotation polarization to form a display image. However, alternative or additional components of display device 200 can be used for display and input sensing functions.

[0028] Other touch sensor configurations are possible. For example, touch sensor 204 can alternatively be implemented in a so-called "on-cell" configuration, in which the touch sensor is disposed directly on display 202. In an example on-cell configuration, touch sensing electrodes can be arranged on a color filter substrate of display 202. However, implementations of touch sensor 204 that are neither configured as in-cell sensors nor as on-cell sensors are also possible. In such implementations, for example, an optically clear adhesive (OCA) can be interposed between display 202 and touch sensor 204.

[0029] Touch sensor 204 can be configured in various structural forms and used for different capacitive sensing modes. In a self-capacitance mode, the capacitance and / or other electrical characteristics (e.g., voltage, charge) between a touch-sensing electrode and ground can be measured to detect an input. In other words, the characteristics of the electrode itself, rather than characteristics with respect to another electrode in the capacitive measurement system, are measured. Additional details regarding self-capacitance touch sensing are described below with respect to Figure 3 Additional details regarding self-capacitance touch sensing are described below with respect to Figure 3 An example self-capacitance touch sensor, which can be implemented in an in-cell or on-cell manner, is shown.

[0030] In a mutual-capacitance mode, the capacitance and / or other electrical characteristics between different electrical states of electrodes can be measured to detect an input. When configured for mutual-capacitance sensing, and similar to the example described above, touch sensor 204 can include a plurality of vertically separated row and column electrodes that form capacitive plate-like nodes at row / column intersections when the touch sensor is driven. The capacitance and / or other electrical characteristics of the nodes can be measured to detect an input.

[0031] When configured as a capacitive sensor, touch sensor 204 can include a plurality of electrodes that are selectively driven to receive an input. The plurality of electrodes can take a number of suitable forms, including but not limited to (1) elongated traces as in a row / column electrode configuration, where rows and columns are arranged in a substantially perpendicular or oblique angle to each other; (2) substantially continuous pads, as in a mutual-capacitance configuration where the pads are arranged in a substantially common plane and divided into subsets of drive and receive electrodes, or as in an in-cell or on-cell configuration; (3) a grid; and (4) an array of isolated (e.g., planar and / or rectangular) electrodes, each arranged at a respective x / y location, as in an in-cell or on-cell configuration.

[0032] In some scenarios, touch sensor 204 can identify the presence of an input source by driving at least one subset of electrodes and analyzing the output resulting from such driving at the same or different subset of electrodes. For mutual-capacitance implementations, a driving signal, also referred to herein as an "excitation waveform," such as a time-varying voltage, can be applied to a first subset of electrodes (e.g., "drive" electrodes), thereby influencing an output signal at a second subset of electrodes (e.g., "receive" electrodes). The presence of an input source can then be ascertained by analyzing the output signal, as described below.

[0033] For self-capacitance implementations, one or more electrode characteristics can be analyzed to identify the presence of an input source. Typically, this is accomplished via driving an electrode with a drive signal and observing electrical behavior with receive circuitry attached to the electrode. For example, the charge accumulation at the electrode resulting from the application of the drive signal can be analyzed to ascertain the presence of an input source. In these example approaches, the type of input source affecting the measurable characteristic of the electrode can be identified, such as a human finger, which can affect the electrode condition by providing a capacitive path to ground for the electromagnetic field. Other approaches can be used to identify different input source types, such as those having active electronics.

[0034] In both mutual and self-capacitance implementations, the touch sensor 204 can employ a correlation-based approach to analyze the output signals to perform input source detection and other possible tasks. In this approach, a given output signal can be correlated with one or more reference sequences using a suitable correlation operation (e.g., cross-correlation) to obtain a correlation output having a sufficient signal-to-noise ratio. The correlation operation can produce a numerical value that can be compared to a threshold, such that if the numerical value meets or exceeds the threshold, the touch sensor 204 determines that an input source is present, while if the numerical value is below the threshold, the touch sensor determines that an input source is not present. In some examples, the drive signal used to drive the electrodes can be used as the reference sequence. In addition, one or more reference sequences can be designed to mitigate noise for certain operating conditions, noise sources, and / or wavebands.

[0035] Figure 3 An example touch sensor 300 is shown. The touch sensor 300 includes a plurality of electrodes, such as electrodes 302, one or more of which are selectively driven to receive inputs having one or more forms described above (e.g., touch, hover, force / pressure, stylus / active input device). The description above is in the context of an in-cell implementation Figure 3 where the touch sensor 300 is configured as an in-cell sensor in combination with a display described above. As such, the touch sensor 300 can be the touch sensor 204 of the touch-sensitive display device 200 in Figure 2 However, the touch sensor 300 can be implemented as an on-cell touch sensor, or neither an in-cell nor on-cell touch sensor, but rather discrete and separate from the display. For in-cell and on-cell implementations, the plurality of electrodes are referred to herein as a plurality of "sensels."

[0036] To enable sensing point charging, each sensing point is operatively coupled to drive circuitry 304. Each sensing point is selectively driven with one or more drive signals via drive circuitry 304. To enable sensing of touch input, each sensing point is operatively coupled to receive circuitry 306. In particular, one or more electrical characteristics (e.g., capacitance, voltage, charge) of each sensing point affected by such driving via drive circuit 304 are monitored via receive circuitry 306 to perform input sensing. Receive circuitry 306 can perform correlation operations on the output received from each sensing point as described above with reference to Figure 2 In one example, the output from a given sensing point can be used for correlation operations after the sensing point is iteratively charged an integer number of times over an integration period. Alternatively or additionally, a sensing point can be continuously monitored during charging. In either case, self-capacitance of multiple sensing points is measured for input sensing.

[0037] As a relatively large number of sensing points are included in typical implementations of touch sensor 300, for simplicity / clarity, Figure 3 A limited number of sensing points are shown in FIG. 1. The examples described below contemplate a particular configuration in which touch sensor 300 includes 20,000 sensing points - e.g., when implemented in a large format display device. However, touch sensor 300 can include any suitable number of sensing points.

[0038] In one example, touch sensor 300 includes 20,000 sensing points arranged in 100 rows and 200 columns. While it can be desirable to maximize sensing frequency by simultaneously measuring capacitance at each sensing point, this would require a large amount of processing and hardware resources to be provided. In particular, 20,000 receivers (e.g., analog-to-digital converters) in receive circuitry 306 would be required to perform full-granularity, simultaneous self-capacitance measurements at each sensing point. As such, a partial-granularity, multiplexed self-capacitance measurement approach can be employed to reduce the size of receive circuitry 306.

[0039] Figure 3One example approach to partial-granularity self-capacitance measurement in touch sensor 300 is illustrated, in which the sense points are grouped into horizontal bands 308A-308D, each having 25 rows of sense points. In this approach, the self-capacitance measurements are multiplexed in time via multiplexer 310, such that a respective measurement time slot is provided for each band 308 in a touch-sensing frame. Accordingly, receive circuitry 306 can include a number of receivers equal to the number of sense points in a given band 308 - e.g., 5000 receivers. However, any suitable number and geometry of grouping of sense points can be used in a multiplexing scheme to reduce the volume of receive circuitry. Further, similar grouping can be performed to reduce the volume of drive circuitry 306, instead of or in addition to using partial-granularity receive circuitry.

[0040] Touch sensor 300 can employ various modes to affect sense point operation to perform input sensing. These modes can sometimes be referred to as "search modes." In one example search mode, all sense points are driven to generate waveforms that can be affected by touch input and / or received by a stylus within range of touch sensor 300. By driving all sense points simultaneously, drive circuitry 304 can be simplified. When combined with the partial-granularity measurement described above, all sense points can be driven even if only a single band 308 is read at any given time. Drive circuitry 304 can apply a single drive signal during a mode, different drive signals during the mode, or can employ multiple modes with different drive signals. Further, drive circuitry 304 can switch between two or more modes to change input source detection and / or to facilitate communication with an active input device such as an active stylus.

[0041] In some implementations, the drive circuitry 304 can employ an "all search" mode and a "local search" mode. In all search, and in conjunction with partial-granularity measurements, the strips 308 are continuously searched to detect finger touches and other input sources such as active or passive styluses. In addition to presence, all search can also indicate a specific location (e.g., in the form of x / y coordinates relative to the touch sensor 300) of certain types of detected input sources (e.g., passive sources such as fingers). However, the location of active input devices such as active styluses indicated by all search can be subject to some degree of uncertainty - e.g., all search can be configured to determine only an approximate or rough location of the input device (such as a strip 308), rather than a specific x / y location within the identified strip. For example, speed / timing constraints and / or signal-to-noise ratios can limit the precision of the location determination. As such, a local search operation can follow all search to determine a specific x / y input device location. In local search, the particular strip 308 in which the input device is (roughly) identified by all search is more thoroughly examined to determine a specific x / y input device location.

[0042] With reference to active stylus 312, the stylus includes an electrode tip 314 (and possibly additional electrodes) configured to capacitively couple with one or more electrodes 302 of touch sensor 300. Stylus 312 is configured to electrostatically transmit signals to and / or receive signals from touch sensor 300 via electrode tip 314. Stylus 312 further includes receive circuitry 316 and transmit circuitry 318. Receive circuitry 316 is configured to interpret a response on electrode tip 314 when a waveform is driven on one or more electrodes 302 of touch sensor 300. Touch sensor 300 can transmit any suitable waveform to convey different types of information to stylus 312. For example, when stylus 312 is proximate to touch sensor 300, touch sensor 300 can transmit a synchronization waveform to cause stylus 312 to become synchronized with touch sensor 300. Transmit circuitry 318 is configured to drive electrode tip 314 to transmit one or more waveforms to touch sensor 300. Stylus 312 can transmit any suitable waveform to convey different types of information to touch sensor 300. In some examples, stylus 312 can transmit a waveform to touch sensor 300 in order to determine the stylus's position during full and partial searches. In one example, the waveform is based on a drive signal applied to a sense point by drive circuitry 304, which causes the sense point to output in the presence of a finger proximate to touch sensor 300, which output is similar to that caused by a finger, but opposite in polarity. In another example, the waveform transmitted by the stylus electrode to a sense point is orthogonal to the waveform produced by a finger touch. These examples can allow touch sensor 300 to simultaneously detect stylus 312 and a finger.

[0043] Generally, the communication between stylus 312 and touch sensor 300 can be used to (1) determine the stylus's position relative to the touch sensor; (2) send / receive synchronization signals to establish / maintain a shared sense of time between the stylus and the touch sensor; (3) convey status / present conditions between the stylus and the digitizer, such as an identifier, stylus button status, battery level, etc.; and / or (4) transmit various other data, such as force determined in the stylus tip, firmware updates, encryption keys / information, times of various event occurrences, etc. Although not shown in FIG. 3, touch sensor 300 and stylus 312 can include components configured to enable radio communication therebetween, which can perform one or more of the functions described above and / or other functions. Figure 3

[0044] ​Some instances of full and / or partial search can be accompanied by a synchronization period to enable time synchronization between the touch sensor 300 and the stylus 312. The synchronization period can enable the stylus 312 to ascertain when to allow signal transmission to the touch sensor 300 (e.g., during full and / or partial search) and when to listen for signals from the touch sensor (e.g., so that a synchronization signal can occur). As such, in some examples, a full touch sensing frame can include a synchronization period followed by full and partial search. As an example, the touch sensor 300 can employ a frame rate of 40-50 Hz to 120 Hz and higher. The synchronization period is also referred to herein as a “stylus synchronization subframe,” and sensing points driven as part of the synchronization frame are referred to herein as “synchronization driven” sensing points or electrodes.

[0045] As used herein, a “full search” mode is a mode in which all electrodes of a touch sensor are “searched.” This full search process can occur simultaneously by listening at each sensing point, or can occur over time by multiplexing receive circuitry to different sensing point regions or bands over time. In a full search mode, all electrodes of the touch sensor 300 can be searched within a specified period (e.g., a touch sensing frame). As used herein, a “partial search” mode is a mode in which a particular region or band of sensing points is serviced during a specified duration (e.g., a touch sensing frame), while other sensing points outside the particular region or band are not serviced. Sensing points within the specified band can be serviced as part of any suitable operation. For example, sensing points within the specified region or band can be multiplexed to receive circuitry to determine the precise location of an active stylus.

[0046] In some implementations, the touch sensor 300 can be configured to operate in a full search only mode, in which the touch sensor 300 performs only full searches and does not perform partial searches. The touch sensor 300 can operate in this mode when the receive circuitry 306 has not received a waveform from the stylus 312 for a threshold duration. In other words, the touch sensor 300 can operate in this mode when the stylus 312 (and any other active stylus) is not within a detectable range of the touch sensor 300. The threshold duration can be set to any suitable duration. In one example, the threshold duration is three seconds.

[0047] When operating in the full search only mode, the touch sensor can use Figure 4The first touch sensing frame 400 is initiated by a stylus synchronization subframe 402, in which the touch sensor 300 transmits a synchronization waveform to the stylus 312. If the stylus 312 is within range of the touch sensor 300, the stylus 312 receives the synchronization waveform with sufficient strength above a threshold. The stylus 312 uses the synchronization waveform to achieve shared time sense between the stylus 312 and the touch sensor 300. In other words, time synchronization between the stylus 312 and the touch sensor 300 is triggered by the stylus receiving the synchronization waveform. This enables the stylus 312 to gain knowledge of the proper time to transmit selected waveforms and information to the touch sensor 300. The synchronization subframe 402 is followed by a plurality of full search subframes 404 (e.g., 404A-404H). Each full search subframe 404 is represented in Figure 4 along with the band or subset of sensing points being searched in A for example. Subframe 404A is depicted as FS(BAND

[0048] In the full search only mode, because no waveforms are received from the stylus 312, the precise stylus position cannot be determined. As such, the local search subframes can be omitted from the first touch sensing frame 400. By omitting the local search subframes from the first touch sensing frame 400, the number of full search subframes that can be included in the first touch sensing frame 400 can be increased. In the illustrated example, each local search subframe is replaced by a full search subframe in the first touch sensing frame 400. Specifically, bands 308A-308D are scanned twice during the first touch sensing frame 400. This effectively doubles the frame rate of the touch sensor 300 in order to detect finger touches and to detect the coarse position of the stylus 312 when the stylus 312 is detected by the touch sensor 300. As such, the touch sensing performance of the touch sensor 300 can be increased when the touch sensor 300 operates in the full search only mode and uses the first touch sensing frame 400.

[0049] In some implementations, when the stylus 312 is outside of the range to receive the synchronization waveforms from the touch sensor 300, the stylus can operate in a sleep mode in which the stylus does not transmit waveforms via the electrode tip 314. However, the stylus 312 can still receive waveforms via the electrode tip 314 in the sleep mode. For example, the sleep mode can be employed to conserve battery power of the stylus. When the stylus 312 does receive the synchronization waveforms from the touch sensor 300, the stylus can "wake up" and begin transmitting "positioning" waveforms that can be received by the touch sensor 300.

[0050] Once the touch sensor 300 detects the positioning waveform from the stylus 312, the touch sensor 300 switches to operating in the full and partial search mode. The touch sensor 300 can operate in the full and partial search mode if the touch sensor has received the positioning waveform from the stylus 312 for a threshold duration of time. In this mode, the touch sensor 300 uses Figure 5 The second touch sensing frame 500 shown performs full and partial search. The second touch sensing frame 500 is initiated by a stylus synchronization subframe 502, in which the touch sensor 300 transmits a synchronization waveform to the stylus 312. The stylus synchronization subframe 502 is followed by a full search subframe 504A. In some examples, the full search subframe 504A can yield a sufficiently accurate position of a touch input (e.g., applied by a human finger or other passive input source), but an insufficiently accurate position of the stylus 312. As such, a partial search subframe 506A can follow the full search subframe 504A to refine the initial estimated position of the stylus 312, as described above. In particular, the results from the full search subframe 504A indicate the presence / approximate position of the stylus 312 in a particular band (e.g., BAND N (“band”) N )). As such, the full search subframe 504A is followed by a partial search subframe 506A (denoted LS(BAND N (“local search (band”) N )) in Figure 5 , indicating a partial search in the particular band 308N identified by the full search subframe 504A.

[0051] Figure 5 Additional full search subframes are also depicted, each followed by a corresponding partial search subframe in that band 308: a full search subframe 504B in band 308B, followed by a partial search subframe 506B in band 308N; a full search subframe 504C in band 308C, followed by a partial search subframe 506C in band 308N; and a full search subframe 504D in band 308D, followed by a partial search subframe 506D in band 308N. From the above, it will be understood that the bands 308 multiplexed to the receive circuitry 306 can differ between full and partial search subframes - e.g., where the band 308 of the partial search subframe prompted by a previous full search subframe can differ from the band 308 multiplexed to the receive circuitry 306 during execution of the previous full search subframe.

[0052] In some implementations, a local search subframe can be used to refine the uncertain position of the active stylus, such as band 308. Specifically, during a local search subframe, a local search can be performed in the identified band after a coarse position is determined via the full search to resolve the position to a desired accuracy, such as a specific x / y position of the active stylus. In other implementations, the full search and local search subframes can yield the same level of position accuracy, and the local search subframe can be used to increase the frame rate of detecting the active stylus position. In other words, the local search subframe can be used to update the position of the active stylus with the same level of precision as the initial position estimate determined during the full search subframe.

[0053] Further, in some implementations, the position of the active stylus can be determined during the full search subframe, and the local search subframe can be dedicated to receiving stylus state information from the active stylus at the touch sensor 300. For example, the stylus state information can include information about battery level, firmware version, tip force / pressure values, and / or button state, among other possible data. The full and local search touch sensing frame can include multiple local search subframes to receive the stylus state information multiple times within the touch frame. In this way, the increased frequency of receiving the stylus state information can reduce the latency of active stylus operation. Further, other uses of the local search subframe are possible.

[0054] In the example touch sensing frames described above, the stylus synchronization subframe initiates the touch sensing frame, but implementations are contemplated in which the synchronization subframe occurs at other temporal locations within the touch sensing frame. Implementations are also contemplated in which two or more stylus synchronization subframes are included within the touch sensing frame.

[0055] The touch sensor 300 can vary the inclusion and duration of the synchronization period, full search, and local search on a frame-to-frame basis. For example, the composition of the frame can be adjusted in view of a longer duration of the local search relative to the full search, which can be a result of more fine or complex measurements and / or processing in the local search.

[0056] The touch sensor 300 can be configured to switch back to operating in the full search only mode based on not receiving a waveform from the stylus 312 (or any other active stylus) for more than a threshold duration. In other words, when the stylus 312 has moved out of the electrostatic communication range, the touch sensor 300 switches to using the first touch sensing frame to increase passive touch sensing performance.

[0057] As discussed above, the stylus 300 can not be aware of which mode the touch sensor is operating in. To send a waveform that can be accurately interpreted by the touch sensor 300, the stylus 312 can use Figure 6The communication frame 600 can be initiated upon receiving a synchronization waveform from the touch sensor 300 during a receive synchronization waveform subframe 602. The synchronization subframe 602 is followed by a position subframe 604A. During the position subframe 604A, the stylus 312 transmits a first waveform (sometimes referred to as a "positioning waveform") that can be used by the touch sensor 300 to position the stylus 312. For example, the positioning waveform can be based on a waveform driven on the electrodes 302 of the touch sensor 300 for detecting finger touches as well as touches from other passive sources. In some implementations, the positioning waveform can be orthogonal or have opposite polarity to the waveforms generated by a finger touch.

[0058] In addition, a report subframe 606A can follow the position subframe 604A to transmit status information about the stylus or other data. During the report subframe 606A, for example, the stylus 312 can transmit one or more waveforms that encode data bits. For example, the data bits can include information about the stylus 312 (or other information). For example, such stylus information can include a touch force, such as a pressure measured by a pressure sensor (not shown) of the stylus 312. Other information can include an identifier, stylus button status, battery level, firmware updates, encryption keys / information, times of various event occurrences, etc. These are just some non-limiting examples. During the report subframe 606A, if the stylus 312 determines that the touch force is zero - i.e., the stylus is hovering - the stylus 312 transmits a positioning waveform to the touch sensor 300 to indicate that the stylus is hovering. If the stylus 312 determines that the touch force is non-zero, the stylus 312 transmits one or more additional waveforms to the touch sensor 300 that are different from the positioning / hovering waveform. The one or more additional waveforms encode data bits representing stylus information such as the touch force (and / or other data). The stylus information can be encoded in the one or more additional waveforms in any suitable manner. For example, the stylus information can be encoded into the one or more additional waveforms via binary phase shift keying (BPSK). Figure 6 Additional position subframes 604B-604D are also depicted, each followed by a respective report subframe 606B-606D during which different waveforms can be transmitted to the touch sensor 300 in the same manner as described above.

[0059] In some examples, the communication schemes described herein can reduce the likelihood of errors in stylus-display electrostatic communications. The communication schemes can be used to Figures 4-6 One example illustration for which this can be seen is in the context of the touch sensing and communication frames shown in FIG. 6. When the stylus 312 is out of range, in typical examples its tip electrode is turned off and does not transmit (e.g., to conserve power), at which time the touch sensor 300 can operate to detect finger touches in a full search only mode (Figure 4 ). When the stylus moves towards the touch sensor, at some point it is close enough that the sync waveform (subframe 402) can be received. The stylus then acquires the timing shared with the touch sensor, and starts transmitting on its tip electrode 314 in the frame structure shown, i.e. waveforms in alternating position subframes and reporting subframes. Figure 6

[0060] At some point after the stylus starts transmitting, the touch sensor 300 first receives a waveform transmitted from the stylus 312, which triggers the touch sensor to switch from the subframe structure of Figure 4 to the subframe structure of Figure 5 . Thus, for some time, the stylus is active and uses the protocol of Figure 6 , while the touch sensor is still operating in a mode that assumes no stylus is present ( Figure 4 ). One of the concepts is a mode mismatch - the stylus is present (and possibly transmitting interfering waveforms), while the touch sensor is operating in a mode where all of its relevant time slots are allocated for detecting finger touches.

[0061] In some examples, the stylus can not know in which mode the touch sensor is, as described elsewhere. This can be desirable and intentional to avoid the increased complexity and resource consumption associated with the communication mode state. Thus, the mode mismatch referenced above has the particular risk that the stylus will transmit something during one of the subframes that causes false touches or other interference. As described earlier, by design, the position waveforms do not interfere with touch detection. In fact, they can be sent by the stylus during each subframe used for finger touch detection in order to produce a coarse estimate of the stylus position. Figure 4

[0062] The mechanism here thus employs the same waveforms as the "position waveforms" sent during the position subframes, as the "hover waveforms" sent by the stylus during the reporting subframes. Thus, during the mismatch period (when the stylus is actively transmitting while the touch sensor is still using the frame structure of Figure 4 ), the stylus will not transmit any interfering waveforms until it "hovers off". Thus, until the stylus touches the display and exerts a non-zero tip pressure, the stylus will switch to the interfering "report waveforms" (pressure or other data bits). The delay resulting from such waveform selection gives the touch sensor more time to identify the presence of the stylus and switch to a mode ready to receive waveforms that otherwise interfere (i.e. those that can cause false touch detection).

[0063] ​​An extreme timing example illustrating the benefit of this approach is as follows: suppose that a fast-approaching stylus enters the signal range for the first time at exactly one time slot after the touch sensor sends its sync waveform (subframe 402). Then, it will not receive the sync signal until the next frame of the touch sensor begins - almost an entire frame will have passed, and the stylus will have moved closer to the display by the time it receives the beacon and turns on its stylus electrodes. This in turn means that the stylus becomes closer to the display before the touch sensor switches to a mode where it can safely receive waveforms such as those encoding force bits Figure 5 Using a common locate and hover waveform reduces the risk of a stylus matching Figure 4 the entirety of the search subframes of Figure 6 the stylus reporting subframes of

[0064] Figure 7 An example method 700 of causing an active stylus to communicate information to a touch-sensitive device is shown. In one example, the method 700 can be performed by the stylus 312 to communicate information to the touch sensor 300 of the touch-sensitive device 300. In general, the method 700 can be performed by any suitable active stylus. Figure 3

[0065] At 702, the method 700 includes determining whether a sync waveform is received electrostatically from the touch-sensitive device via a capacitive coupling between a stylus electrode of the active stylus and one or more electrodes of a touch sensor of the touch-sensitive device. If the sync waveform is received, the method moves to 704. Otherwise, the method 700 returns to 702 and checks for the sync waveform. At 704, the method 700 includes electrostatically communicating a first waveform to the touch-sensitive device during one or more subframes of a first subset of subframes of a communication frame that is based on a time synchronization with the touch-sensitive device. As referenced above, this first waveform can be referred to as a "locate" waveform. In one example, the first subset of subframes includes the locate subframes 604 of the communication frame 600. The stylus communicates the locate waveform during the first subset of subframes to indicate a location of the stylus to the touch-sensitive device.

[0066] At 706, the method 700 includes determining a touch force of the active stylus. For example, the touch force can include a pressure measured by a pressure sensor of the active stylus. At 708, the method 700 includes determining whether the touch force is non-zero. If the touch force is not non-zero, the method 700 moves to 710 and communicates the first waveform to the touch-sensitive device during a second subset of subframes of the communication frame. In one example, the second subset of subframes includes the report subframes 604 of the communication frame 606. The stylus communicates the first waveform during the second subset of subframes to indicate that the stylus is hovering or has a touch force of zero to the touch-sensitive device. Thus, as described above, the "locate waveform" can be the same as the "hover waveform."​

[0067] Otherwise, the method 700 moves to 712 and transmits one or more additional waveforms to the touch sensitive device during the second subset of subframes. The one or more additional waveforms, the "reporting waveforms," encode touch stylus information to be communicated to the touch sensor. For example, the one or more additional waveforms can encode a non-zero touch force of an active stylus. The active stylus transmits the one or more additional waveforms during the second subset of subframes to indicate the touch stylus information (e.g., the non-zero touch force) to the touch sensitive device. While sending the positioning / hovering waveform or the one or more additional waveforms during the second subset of subframes, the method 700 returns to 702 to repeat the method 700.

[0068] Figure 8 and 9 An example touch sensing method 800 for a touch sensitive device is shown. In one example, the method 800 can be performed by the touch sensor 300 of Figure 3 In general, the method 800 can be performed by any suitable touch sensitive device.

[0069] At 802, the method 800 includes transmitting a synchronization waveform via one or more electrodes of the touch sensor during a full search only touch sensing frame that includes a plurality of full search subframes. At 804, the method 800 includes determining whether a first waveform is received from an electrode tip of an active stylus during a full search subframe of the full search only touch sensing frame. As referenced above, this first waveform can be referred to as a "positioning" waveform. If the positioning waveform is received from the active stylus, the method moves to 806. Otherwise, the method 800 returns to 802 and retransmits the synchronization waveform during the next touch sensing frame. At 806, the method 800 includes identifying a coarse position of the active stylus based on the positioning waveform and a band or region of the touch sensor corresponding to the full search subframe in which the positioning waveform was received.

[0070] Because the touch sensitive device is operating in full search only mode when the positioning waveform is received, the touch sensitive device switches to operating in full and partial search mode based on receiving the positioning waveform. At 808, the method 800 includes transmitting a synchronization waveform during a full and partial search touch sensing frame. The full and partial search touch sensing frame includes a plurality of full search subframes interleaved with a plurality of partial search subframes. At 810, the method 800 includes determining whether a first waveform is received during the full search subframe(s) of the full and partial search touch sensing frame. If the positioning waveform is received during the full search subframe(s), the method moves to 812 and determines a position of the active stylus based on the positioning waveform. In some implementations, this initial position determination is a coarse position determination (e.g., a band of the touch sensor). Otherwise, the method 800 moves to 826.

[0071] At 814, the method 800 includes determining whether a position waveform is received during the local search subframe(s) of the full and local search touch-sensing frame. If a position waveform is received during the local search subframe(s), the method moves to 816. Otherwise, the method 800 returns to 820. At 816, the method 800 includes updating the position of the active stylus based on the position waveform. In some implementations that initially determine a coarse position, updating the position of the active stylus includes determining a more precise position of the active stylus. In other implementations, updating the position of the active stylus includes updating the position with the same level of precision. At 818, the method 800 includes determining that the active stylus is hovering based on the position waveform. Thus, as described above, the "position waveform" can be the same as the "hovering waveform." In one example, the position waveform can encode a touch force equal to zero, which can be interpreted by the touch sensor as the active stylus being hovering.

[0072] At 820, the method 800 includes determining whether one or more additional waveforms different from the position waveform are received during the local search subframe(s) of the full and local search touch-sensing frame. As referenced above, these one or more additional waveforms can be referred to as "report" waveforms, which encode stylus information (and / or other information). If one or more additional waveforms are received during the local search subframe(s), the method moves to 822. Otherwise, the method 800 returns to 810. At 822, the method 800 includes updating the position of the active stylus based on the one or more additional waveforms. In some implementations that initially determine a coarse position, updating the position of the active stylus includes determining a more precise position of the active stylus. In other implementations, updating the position of the active stylus includes updating the position with the same level of precision. At 824, the method 800 includes determining stylus information of the active stylus based on the one or more additional waveforms. For example, the one or more additional waveforms can encode a touch force of the active stylus.

[0073] At 826, the method 800 can include determining whether a threshold duration has passed without receiving the first waveform. If the position waveform has been received within the threshold duration, the method 800 returns to 810 and the touch-sensitive device continues to operate in the full and local search mode. Otherwise, the threshold duration has passed without receiving the position waveform, the method 800 returns to 802 and the touch-sensitive device switches back to operating in the full search only mode.

[0074] In some implementations, the methods and processes described herein can be tied to a computing system of one or more computing devices. In particular, such methods and processes can be implemented as a computer-application or service, an application-programming interface (API), a library, and / or other computer-program product.

[0075] Figure 10 A non-limiting example of a computing system 1000 that can perform one or more of the above-described methods and processes is schematically illustrated. The computing system 1000 is shown in simplified form. The computing system 1000 can take the form of one or more personal computers, server computers, tablet computer(s), home-entertainment computers, network computing devices, gaming devices, mobile computing devices, mobile communication devices (e.g., smart phone(s)), and / or other computing devices. For example, the computing system 1000 can represent the interactive display system 100, the touch-sensitive display device 200, and generally any appropriate touch-sensitive device discussed herein.

[0076] The computing system 1000 includes a logic machine 1002 and a storage machine 1004. The computing system 1000 can optionally include a display subsystem 1006, input subsystem 1008, communication subsystem 1010, and / or other components not shown in FIG. 10. Figure 10

[0077] The logic machine 1002 includes one or more physical devices configured to execute instructions. For example, the logic machine can be configured to execute instructions that are part of one or more applications, services, programs, routines, libraries, objects, components, data structures, or other logical constructs. Such instructions can be implemented to perform a task, implement a data type, transform the state of one or more components, achieve a technical effect, or otherwise arrive at a desired result.

[0078] The logic machine 1002 can include one or more processors configured to execute software instructions. Additionally or alternatively, the logic machine can include one or more hardware or firmware logic machines configured to execute hardware or firmware instructions. The processors of the logic machine can be single-core or multi-core, and the instructions executed thereon can be configured for sequential, parallel, and / or distributed processing. Individual components of the logic machine optionally can be distributed among two or more separate devices, which can be remotely located and / or configured for coordinated processing. Aspects of the logic machine can be virtualized and executed by remotely accessible, networked computing devices configured in a cloud-computing configuration.

[0079] The storage machine 1004 includes one or more physical devices configured to hold instructions executable by the logic machine to implement the methods and processes described herein. When the methods and processes are implemented, the state of the storage machine 1004 can be transformed— e.g., to hold different data.

[0080] ​Storage machine 1004 can include one or more physical devices configured to store data and / or instructions for use by logic machine 1002. Storage machine 1004 can include removable storage and / or non-removable storage including, for example, optical, semiconductor, magnetic, and / or other storage media. Storage machine 1004 can include volatile, nonvolatile, dynamic, static, read / write, read-only, random access, sequential access, location- dependent, file- dependent, and / or content- dependent devices. Storage machine 1004 can include a non-transitory computer-readable medium.

[0081] It will be appreciated that storage machine 1004 includes one or more physical devices. However, aspects of the instructions described herein can alternatively be propagated by a communication medium (e.g., an electromagnetic signal, an optical signal, etc.) that is not held by a physical device for a finite duration.

[0082] Aspects of logic machine 1002 and storage machine 1004 can be integrated into one or more hardware-logic components. Such hardware-logic components can include field-programmable gate arrays (FPGAs), program- and application-specific integrated circuits (PASIC / ASICs), program- and application-specific standard products (PSSP / ASSPs), system-on-a-chip (SOC), and complex programmable logic devices (CPLDs), for example.

[0083] When included, display subsystem 1006 can be used to present a visual representation of data held by storage machine 1004. This visual representation can take the form of a graphical user interface (GUI). As the herein described methods and processes change the data held by the storage machine, and thus transform the state of the storage machine, the state of display subsystem 1006 can likewise be transformed to visually represent changes in the underlying data. Display subsystem 1006 can include one or more display devices using virtually any type of technology. Such display devices can be combined with logic machine 1002 and / or storage machine 1004 in a shared enclosure, or such display devices can be peripheral display devices.

[0084] When included, input subsystem 1008 can comprise or interface with one or more user-input devices such as a keyboard, mouse, touch screen, or game controller. In some embodiments, the input subsystem can comprise or interface with selected natural user input (NUI) componentry. Such componentry can be integrated or peripheral, and the transduction and / or processing of input actions can be handled on- or off-board. Example NUI componentry can include a microphone for speech and / or voice recognition; an infrared, color, stereoscopic, and / or depth camera for machine vision and / or gesture recognition; a head tracker, eye tracker, accelerometer, and / or gyroscope for motion detection and / or intent recognition; as well as electric-field sensing componentry for assessing brain activity.

[0085] When included, communication subsystem 1010 can be configured to communicatively couple computing system 1000 with one or more other computing devices. Communication subsystem 1010 can include wired and / or wireless communication devices compatible with one or more different communication protocols. As non-limiting examples, the communication subsystem 1010 can be configured for communication via a wireless telephone network, or a wired or wireless local- or wide-area network. In some implementations, the communication subsystem 1010 can allow computing system 1000 to send and / or receive messages to and / or from other devices via a network such as the Internet.

[0086] In one example, a touch sensitive device includes: a capacitive based touch sensor including a plurality of electrodes, drive circuitry configured to selectively drive the plurality of electrodes with a synchronization waveform to time synchronize an active stylus with the touch sensitive device; receive circuitry configured to interpret a response on one or more of the plurality of electrodes to determine a position of the active stylus, the response caused by a first waveform driven on a stylus electrode of the active stylus; and wherein the touch sensitive device is configured to: 1) when the first waveform from the active stylus is received via the one or more of the plurality of electrodes at a first time relative to the synchronization waveform being transmitted, determine the position of the active stylus based on the first waveform being received at the first time, 2) when the first waveform is received via the one or more of the plurality of electrodes at a second time relative to the synchronization waveform being transmitted, determine whether the active stylus is hovering based on the first waveform being received at the second time, and 3) when one or more additional waveforms are received via the one or more of the plurality of electrodes at the second time, determine stylus information of the active stylus based on the one or more additional waveforms being received at the second time. In this example and / or other examples, the touch sensitive device can be configured to: 1) when the touch sensitive device has not received the first waveform for more than a threshold duration, use a first touch sensing frame to scan for input to the capacitive based touch sensor, the first touch sensing frame including a first set of subframes, and 2) when the touch sensitive device has received the first waveform for less than the threshold duration, use a second touch sensing frame to scan for input to the capacitive based touch sensor, the second touch sensing frame including a second set of subframes different than the first set of subframes. In this example and / or other examples, the first set of subframes can include a first plurality of full search subframes, each full search subframe can correspond to a subset of electrodes selected from the plurality of electrodes, and during each full search subframe, the receive circuitry can be configured to connect via selective multiplexing to the electrodes of the respective subset to determine the position of the active stylus based on the first waveform being received via the one or more electrodes of the respective subset. In this example and / or other examples, the second set of subframes can include a second plurality of full search subframes and a plurality of local search subframes, during each full search subframe of the second plurality of full search subframes, the receive circuitry can be configured to connect via selective multiplexing to the electrodes of the respective subset to determine the position of the active stylus based on the first waveform being received via the one or more electrodes of the respective subset, and during each local search subframe, the receive circuitry can be configured to connect via selective multiplexing to the electrodes of a selected subset corresponding to the position of the active stylus to update the position of the active stylus based on the first waveform or the one or more additional waveforms being received via the one or more electrodes of the selected subset. In this example and / or other examples, the plurality of full search subframes can be interleaved with the plurality of local search subframes in the second touch sensing frame.In this and / or other examples, a duration of the full search subframe of the first touch sensing frame can be equal to a duration of the full search subframe of the second touch sensing frame, and can further be equal to a duration of the partial search subframe of the second touch sensing frame. In this and / or other examples, the touch sensitive device can be configured to determine passive touch input based on the second waveform driven on one or more electrodes of the plurality of electrodes of the capacitive-based touch sensor during the full search subframes of the first touch sensing frame and the second touch sensing frame. In this and / or other examples, the first waveform and the second waveform can be orthogonal or have opposite polarities with respect to each other. In this and / or other examples, the stylus information can include a non-zero touch force of an active stylus encoded into one or more additional waveforms.

[0087] In one example, a touch sensing method for a touch sensitive device including a capacitive-based touch sensor including a plurality of electrodes, the method including transmitting a synchronization waveform via one or more of the plurality of electrodes, determining a position of an active stylus based on a first waveform being received via one or more of the plurality of electrodes at a first time relative to the synchronization waveform being transmitted being received at the first time, determining that the active stylus is hovering based on the first waveform being received at a second time relative to the synchronization waveform being transmitted being received via one or more of the plurality of electrodes at the second time, and determining stylus information of the active stylus based on one or more additional waveforms being received via one or more of the plurality of electrodes at the second time. In this example and / or other examples, the method can further include using a first touch sensing frame to scan for input to the capacitive-based touch sensor when the first waveform has not been received for more than a threshold duration, the first touch sensing frame including a first set of subframes, the first set of subframes including a first plurality of full search subframes, each full search subframe corresponding to a subset of electrodes selected from the plurality of electrodes, determining the position of the active stylus based on a full search subframe of the first touch sensing frame during which the first waveform is received, using a second touch sensing frame to scan for input to the capacitive-based touch sensor when the first waveform is received for the threshold duration, the second touch sensing frame including a second set of subframes, the second set of subframes including a second plurality of full search subframes and a plurality of local search subframes, the first waveform being received during a full search subframe of the second touch sensing frame, updating the position of the active stylus based on the full search subframe of the second touch sensing frame during which the first waveform is received, determining that the active stylus is hovering based on the first waveform when the first waveform is received during a local search subframe, determining stylus information of the active stylus based on one or more additional waveforms when the one or more additional waveforms are received during the local search subframe, and updating the position of the active stylus based on the first waveform or the one or more additional waveforms being received during the local search subframe. In this example and / or other examples, the plurality of full search subframes can be interleaved with the plurality of local search subframes in the second touch sensing frame. In this example and / or other examples, a duration of the full search subframes of the first touch sensing frame can be equal to a duration of the full search subframes of the second touch sensing frame and can further be equal to the local search subframes of the second touch sensing frame. In this example and / or other examples, the touch sensitive device can be configured to determine passive touch input based on a second waveform driven on one or more of the plurality of electrodes of the capacitive-based touch sensor during the full search subframes of the first touch sensing frame and the second touch sensing frame.In this and / or other examples, the first waveform and the second waveform can be orthogonal or have opposite polarities with respect to each other. In this and / or other examples, the stylus information can include a non-zero touch force of the active stylus encoded into one or more additional waveforms.

[0088] In an example, an active stylus includes a stylus electrode configured to capacitively couple with one or more electrodes of a capacitive-based touch sensor of a touch-sensitive device, receiving circuitry operably coupled to the stylus electrode and configured to receive a synchronization waveform from the touch-sensitive device, and transmitting circuitry operably coupled to the stylus electrode and configured to transmit information to the touch-sensitive device according to a communication frame including a first set of sub-frames and a second set of sub-frames upon receiving the synchronization waveform, where the transmitting circuitry is configured to: 1) transmit a first waveform during one or more sub-frames of the first set, 2) transmit the first waveform during one or more sub-frames of the second set if the active stylus is hovering, and 3) transmit one or more additional waveforms during one or more sub-frames of the second set if the active stylus is not hovering. In this and / or other examples, the one or more additional waveforms can encode stylus information. In this and / or other examples, the stylus information can include a non-zero touch force of the active stylus. In this and / or other examples, the sub-frames of the first set can be interleaved with the sub-frames of the second set in the communication frame.

[0089] It should be understood that the configurations and / or approaches described herein are exemplary in nature, and that these specific embodiments or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein can represent one or more of any number of processing strategies. As such, various acts illustrated and / or described can be performed in the sequence illustrated and / or described, in other sequences, in parallel, or omitted. Likewise, the order of the above-described processes can be changed.

[0090] The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various processes, systems and configurations, other features, functions, acts, and / or properties disclosed herein, as well as any and all equivalents thereof.

Claims

1. An active stylus, comprising: Stylus electrodes, the stylus electrodes being configured to be capacitively coupled to one or more electrodes of a capacitive touch sensor of a touch-sensitive device; A receiving circuit system operatively coupled to the stylus electrodes and configured to receive a synchronization waveform from the touch-sensitive device; as well as A transmission circuitry system operatively coupled to the stylus electrodes and configured to, upon receiving the synchronization waveform, transmit stylus information to the touch-sensitive device according to a communication frame comprising a first set of positioning subframes and a second set of reporting subframes, the first set of positioning subframes for transmitting waveforms indicating the position of the active stylus, and the second set of reporting subframes for transmitting waveforms indicating stylus status information, wherein the transmission circuitry system is configured to: 1) transmit a first waveform during one or more positioning subframes in the first set, 2) transmit the first waveform during one or more reporting subframes in the second set, at least in part based on the active stylus being hovered, and 3) transmit one or more additional waveforms during one or more reporting subframes in the second set, at least in part based on the active stylus not being hovered.

2. The active stylus as described in claim 1, characterized in that, The one or more additional waveforms encode stylus state information, which includes the non-zero touch force of the active stylus.

3. The active stylus as described in claim 1, characterized in that, The one or more additional waveforms encode stylus status information, which includes one or more of the following: stylus button status, battery level, firmware update, and encryption key.

4. The active stylus as described in claim 1, characterized in that, The stylus status information is encoded into one or more additional waveforms via binary phase shift keying (BPSK).

5. The active stylus as described in claim 1, characterized in that, In the communication frame, the first set of positioning subframes and the second set of reporting subframes are interleaved.

6. The active stylus as described in claim 1, characterized in that, The touch-sensitive device is configured to determine passive touch input based on a second waveform driven on one or more of the plurality of electrodes of the capacitance-based touch sensor, wherein the first waveform is derived from the second waveform.

7. The active stylus as described in claim 6, characterized in that, The first waveform is at least one of being orthogonal to the second waveform and opposite in polarity.

8. The active stylus as described in claim 1, characterized in that, The active stylus is configured to operate in sleep mode before receiving the synchronization waveform, in which the active stylus does not transmit the waveform via the stylus electrodes.

9. The active stylus as described in claim 8, characterized in that, The one or more additional waveforms encode the stylus information state, which includes the non-zero touch force of the active stylus.

10. The active stylus as described in claim 1, characterized in that, Further includes: A pressure sensor configured to determine the touch force of the active stylus; Furthermore, the transmission circuitry system is configured to determine whether the active stylus is hovering or not based on the touch force.

11. A method for controlling an active stylus, the method comprising: A synchronization waveform is received from the touch-sensitive device via capacitive coupling between the stylus electrodes of the active stylus and one or more electrodes of the capacitive touch sensor of the touch-sensitive device. In response to receiving the synchronization waveform, stylus information is transmitted to the touch-sensitive device according to a communication frame including a first set of positioning subframes and a second set of reporting subframes. The first set of positioning subframes is used to transmit a waveform indicating the position of the stylus, and the second set of reporting subframes is used to transmit a waveform indicating the stylus information. The transmission includes: 1) A first waveform is transmitted via the stylus electrodes during one or more positioning subframes of the first group; 2) The first waveform is transmitted via the stylus electrodes during one or more reporting subframes of the second group, at least in part based on the active stylus being hovered; and 3) At least in part based on the fact that the active stylus is not hovering, one or more additional waveforms are transmitted via the stylus electrodes during one or more reporting subframes of the second group.

12. The method of claim 11, further comprising: Before receiving the synchronization waveform, the active stylus is operated in sleep mode, in which the active stylus does not transmit waveforms via the stylus electrodes.

13. The method as described in claim 11, characterized in that, The one or more additional waveforms encode stylus state information, which includes the non-zero touch force of the active stylus.

14. The method as described in claim 11, characterized in that, The one or more additional waveforms encode stylus status information, which includes one or more of the following: stylus button status, battery level, firmware update, and encryption key.

15. The method as described in claim 11, characterized in that, The stylus status information is encoded into one or more additional waveforms via binary phase shift keying (BPSK).

16. The method as described in claim 11, characterized in that, In the communication frame, the positioning subframes of the first group are interleaved with the reporting subframes of the second group.

17. The method as described in claim 11, characterized in that, The touch-sensitive device is configured to determine passive touch input based on a second waveform driven on one or more of the plurality of electrodes of the capacitance-based touch sensor, wherein the first waveform is derived from the second waveform.

18. The method as described in claim 17, characterized in that, The first waveform is orthogonal to the second waveform.

19. The method as described in claim 17, characterized in that, The first waveform has the opposite polarity to the second waveform.

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