PATENT DOCUMENT

Publication Number: US-11941175-B2
Application Number: US-202318194514-A
Country: US
Kind Code: B2

Title: Skin-to-skin contact detection

Abstract:
Contact or movement gestures between a first body part and a second body part can be detected. Sense circuitry can be configured to sense a signal at the sense electrode (e.g., configured to contact the second body part) in response to a drive signal applied to the drive electrode (e.g., configured to contact the first body part). Processing circuitry can be configured to detect contact in accordance with a determination that one or more criteria are met (e.g., an amplitude criterion and a non-distortion criterion). Additionally or alternatively, processing circuitry can be configured to detect a movement gesture in accordance with a determination that one or more criteria are met (e.g., a contact criterion and a movement criterion).

Claims:
The invention claimed is: 
     
       1. A wearable system for detecting gestures, comprising:
 a wearable device, comprising:
 drive circuitry coupled to a drive electrode and configured to generate a stimulation signal, the drive electrode positioned at a first location in the wearable device for contacting a first finger of a first hand; and 
 sense circuitry coupled to a sense electrode and configured to generate a sense output signal based on one or more sense signals received at the sense electrode in response to the stimulation signal, the sense electrode positioned at a second location in the wearable device for contacting the first finger of the first hand; and 
 
 a processor communicatively coupled to the drive circuitry and the sense circuitry of the wearable device, and configured for:
 capturing an amplitude of the sense output signal over time, and 
 in accordance with a determination that first criteria are met, the first criteria comprising first amplitude and time criteria evaluated for the sense output signal, detecting a making of contact of the first finger of the first hand with a body part different from the first finger of the first hand. 
 
 
     
     
       2. The wearable system of  claim 1 , wherein:
 the body part different from the first finger of the first hand is a second hand that is different from the first hand. 
 
     
     
       3. The wearable system of  claim 1 , further comprising:
 an optical sensor in communication with the processor, wherein the first criteria further comprise: 
 a criterion for an output of the optical sensor that is met when the output of the optical sensor indicates the making of contact of the first finger with the body part different than the first hand. 
 
     
     
       4. The wearable system of  claim 3 , wherein the processor is further configured for:
 in accordance a determination that the output of the optical sensor indicates a making of contact of the first finger with another finger or thumb of the first hand, detecting the making of contact of the first finger with another finger or thumb of the first hand. 
 
     
     
       5. The wearable system of  claim 1 , wherein the wearable device is a first wearable device, wherein the drive electrode is a first drive electrode, wherein the stimulation signal is a first stimulation signal, wherein the sense electrode is a first sense electrode, wherein the sense output signal is a first sense output signal, and wherein the wearable system further comprises:
 a second wearable device, comprising:
 drive circuitry coupled to a second drive electrode and configured to generate a second stimulation signal, the drive electrode positioned at a first location in the second wearable device for contacting a first finger of a second hand; and 
 sense circuitry coupled to a second sense electrode and configured to generate a second sense output signal, the second sense electrode positioned at a second location in the second wearable device for contacting the first finger of the second hand, wherein:
 the first stimulation signal has a first frequency selected from a first set of stimulation frequencies; and 
 the second stimulation signal has a second frequency selected from a second set of stimulation frequencies, the second set of stimulation frequencies being different from the first set of stimulation frequencies. 
 
 
 
     
     
       6. The wearable system of  claim 5 , wherein:
 the processor is configured for detecting the making of contact of the first finger of the first hand with the body part different than the first hand in further accordance with a determination that the first sense output signal has a first component corresponding to the first frequency and has a second component corresponding to the second frequency. 
 
     
     
       7. The wearable system of  claim 6 , wherein the processor is communicatively coupled to the drive circuitry and the sense circuitry of the second wearable device, and further configured for:
 capturing an amplitude of the second sense output signal over time; and 
 in accordance with a determination that second criteria are met, the second criteria comprising the first amplitude and time criteria evaluated for the second sense output signal, detecting a making of contact of the first finger of the second hand with the first hand. 
 
     
     
       8. The wearable system of  claim 7 , wherein the second criteria further comprise:
 a criterion for the second sense output signal that is met when the second sense output signal has a first component corresponding to the first frequency and has a second component corresponding to the second frequency. 
 
     
     
       9. The wearable system of  claim 5 , wherein the processor is communicatively coupled to the drive circuitry and the sense circuitry of the second wearable device, and further configured for:
 in accordance with a determination that the first amplitude and time criteria evaluated for the first sense output signal are met, and a determination that the first sense output signal only corresponds to the first frequency, detecting a making of contact of the first finger of the first hand with a thumb of the first hand; and 
 in accordance with a determination that the first amplitude and time criteria evaluated for the second sense output signal are met, and a determination that the second sense output signal only corresponds to the second frequency, detecting a making of contact of the first finger of the second hand with a thumb of the second hand. 
 
     
     
       10. The wearable system of  claim 5 , wherein the processor is communicatively coupled to the drive circuitry and the sense circuitry of the second wearable device, and further configured for:
 in accordance with a determination that second amplitude and time criteria evaluated for the first sense output signal are met, and a determination that the first sense output signal only corresponds to the first frequency, detecting a making of contact of the first finger of the first hand with another finger or thumb of the first hand; and 
 in accordance with a determination that the second amplitude and time criteria evaluated for the second sense output signal are met, and a determination that the second sense output signal only corresponds to the second frequency, detecting a making of contact of the first finger of the second hand with another finger or thumb of the second hand. 
 
     
     
       11. The wearable system of  claim 10 , wherein:
 the second amplitude and time criteria include the first amplitude and time criteria. 
 
     
     
       12. The wearable system of  claim 10 , wherein the processor is further configured for:
 in accordance with a determination that third amplitude and time criteria evaluated for the first sense output signal are met, following the determination that the second amplitude and time criteria evaluated for the first sense output signal are met, detecting a breaking of contact of the first finger of the first hand with the another finger or thumb of the first hand; and 
 in accordance with a determination that the third amplitude and time criteria evaluated for second sense output signal are met, following the determination that the second amplitude and time criteria evaluated for the second sense output signal are met, detecting a breaking of contact of the first finger of the second hand with the another finger or thumb of the second hand. 
 
     
     
       13. The wearable system of  claim 1 , wherein the determination that the first amplitude and time criteria evaluated for the sense output signal are met comprises:
 determining that the sense output signal satisfies a first voltage threshold during a first time period between a first time and a second time; and 
 determining that the sense output signal changes to satisfy a second voltage threshold at the second time. 
 
     
     
       14. The wearable system of  claim 1 , wherein the wearable device is a first wearable device, wherein the drive electrode is a first drive electrode, wherein the stimulation signal is a first stimulation signal, wherein the sense electrode is a first sense electrode, wherein the sense output signal is a first sense output signal, and wherein the wearable system further comprises:
 a second wearable device, comprising:
 drive circuitry coupled to a second drive electrode and configured to generate a second stimulation signal, the drive electrode positioned at a first location in the second wearable device for contacting a second finger of the first hand; and 
 sense circuitry coupled to a second sense electrode and configured to generate a second sense output signal, the second sense electrode positioned at a second location in the second wearable device for contacting the second finger of the first hand, wherein the processor is communicatively coupled to the drive circuitry and the sense circuitry of the second wearable device, and further configured for:
 capturing an amplitude of the second sense output signal over time; and 
 in accordance with a determination that the first amplitude and time evaluated for the second sense output signal are met, detecting a making of contact of the second finger of the first hand with a body part different than the second finger of the first hand. 
 
 
 
     
     
       15. The wearable system of  claim 14 , wherein:
 the body part different than the second finger of the first hand is a thumb of the first hand. 
 
     
     
       16. The wearable system of  claim 14 , wherein:
 the body part different than the second finger of the first hand is a second hand that is different from the first hand. 
 
     
     
       17. A method for detecting gestures, the method performed at a wearable device including drive circuitry, sense circuitry, and processing circuitry, the method comprising:
 generating a stimulation signal for propagating through a first finger of a first hand; 
 generating a sense output signal based on one or more sense signals received from the first finger of the first hand in response to the stimulation signal; 
 capturing an amplitude of the sense output signal over time; and 
 in accordance with a determination that first amplitude and time criteria are met by the sense output signal, detecting a making of contact of the first finger of the first hand with a body part different than the first finger of the first hand. 
 
     
     
       18. The method of  claim 17 , wherein detecting the making of contact of the first finger of the first hand with the body part different than the first finger of the first hand comprises:
 detecting the making of contact of the first finger of the first hand with a thumb of the first hand; or 
 detecting the making of contact of the first finger of the first hand with a second hand that is different from the first hand. 
 
     
     
       19. The method of  claim 17 , wherein the determination that the first amplitude and time criteria are met by the sense output signal comprises:
 determining that the sense output signal satisfies a first voltage threshold during a first time period between a first time and a second time; and 
 determining that the sense output signal changes to satisfy a second voltage threshold at the second time. 
 
     
     
       20. A wearable device for detecting gestures, comprising:
 drive circuitry comprising a drive electrode positioned within the wearable device to contact a first finger of a first hand; 
 sense circuitry comprising a sense electrode and configured to generate a sense output signal; 
 a processor communicatively coupled to the drive circuitry and the sense circuitry and configured for:
 capturing an amplitude of the sense output signal over time; and 
 in accordance with a determination that first amplitude and time criteria are met by the sense output signal, detecting a making of contact of the first finger of the first hand with a body part different than first finger of the first hand.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/814,826 now U.S. Pat. No. 11,625,098 issued on Apr. 11, 2023), filed on Jul. 25, 2022, which is a continuation of U.S. patent application Ser. No. 17/218,038 (now U.S. Pat. No. 11,397,468 issued on Jul. 26, 2022), filed on Mar. 30, 2021, which is a continuation-in-part (CIP) of U.S. patent application Ser. No. 16/836,552 (now U.S. Pat. No. 11,397,466 issued on Jul. 26, 2022), filed on Mar. 31, 2020, the contents of which are incorporated herein by reference in their entireties for all purposes. 
    
    
     FIELD 
     This relates generally to systems and methods of detecting skin-to-skin contact, and more particularly, to detecting contact between two hands or between two fingers for input in virtual reality or augmented reality environments. 
     BACKGROUND 
     Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens and the like. In some examples, contact between two different parts of a user&#39;s body may be used for input. For example, cameras in a head-mounted display can be used to track movement of fingers to detect a finger in contact with an opposite hand, or to track movement of a finger along an opposite hand surface. Additionally or alternatively, a radiofrequency-based system can be used to detect a finger in contact with an opposite hand, or to track movement of a finger along an opposite hand surface. However, camera-based systems and/or radiofrequency-based systems may have difficulty detecting the difference between a finger touching the opposite hand or proximate to without contacting (hovering above) the opposite hand. Additionally, camera-based systems require the finger and opposite hand be in the field of view of the cameras for operation. 
     SUMMARY 
     This relates to devices and methods of detecting contact between a first body part and a second body part. Sense circuitry can be configured to sense a signal at the sense electrode (e.g., configured to contact the second body part) in response to a drive signal applied to the drive electrode (e.g., configured to contact the first body part). Processing circuitry can be configured to detect contact in accordance with a determination that one or more criteria are met. The one or more criteria can include a first criterion that is met when an amplitude of the sensed signal exceeds an amplitude threshold and a second criterion that is met when the sensed signal has a non-distorted waveform. Using a robust set of criteria, including an evaluation of the quality of the waveform (e.g., whether it is distorted or not), can improve the disambiguation between a skin-to-skin contact event and a proximity event. 
     This also relates to devices and methods of detecting a movement gesture using contact between two fingers of the same hand (e.g., to enable one-handed skin-to-skin input gestures). Sense circuitry can be configured to sense a signal at a sense electrode (e.g., configured to contact a finger of a hand) in response to a drive signal applied to a drive electrode (e.g., configured to contact a different finger of the hand). Processing circuitry can be configured to detect a movement gesture (e.g., a slide gesture) in accordance with a determination that one or more criteria are met. The one or more criteria can include a first criterion indicative of contact between a first finger and a second finger and a second criterion indicative of movement of the first finger along the second finger. 
     This further relates to devices and methods of detecting gestures between a finger of one hand and other body parts (e.g., other fingers or a thumb on the same hand, or the opposing hand) using a single device (e.g., a ring) on the finger of the hand. Sense circuitry in the device can be configured to sense a signal at one or more sense electrodes in the device in response to a drive signal applied to a drive electrode in the device. Processing circuitry can be configured to detect contact or a movement gesture (e.g., a slide gesture) in accordance with a determination that one or more criteria are met. The one or more criteria can include various amplitude criteria, in some instances evaluated over a certain time period. When a particular gesture is detected, an operation can be initiated. 
     This also relates to devices and methods of detecting gestures between a finger of one hand and other body parts (e.g., other fingers or a thumb on the same hand, or the opposing hand) using a device (e.g., a ring) on each of multiple fingers of the same hand, or on fingers of different hands. Sense circuitry in each device can be configured to sense a signal at one or more sense electrodes in the device in response to drive signals applied to a drive electrode in each of the devices. When a particular gesture is detected, an operation can be initiated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS.  1 A- 1 B  illustrate an example system for skin-to-skin contact detection according to examples of the disclosure. 
         FIG.  2    illustrates a block diagram of an example computing system  200  for skin-to-skin contact detection according to examples of the disclosure. 
         FIGS.  3 A- 3 B  illustrate a proximity and a contact, respectively, between a first body part and a second body part according to examples of the disclosure. 
         FIGS.  4 A- 4 B  illustrate time domain and frequency domain representations of the sensed signal corresponding to the proximity or the contact according to examples of the disclosure. 
         FIG.  5    illustrates a block diagram of a correlation circuit  500  according to examples of the disclosure. 
         FIG.  6    illustrates an example process of skin-to-skin contact detection according to examples of the disclosure. 
         FIGS.  7 A- 7 B  illustrate an example system for detection of a skin-to-skin gesture according to examples of the disclosure. 
         FIGS.  8 A- 8 C  illustrate time domain representations and frequency domain representations of the sensed signal corresponding to a finger-to-finger slide gesture according to examples of the disclosure. 
         FIG.  9    illustrates an example process of skin-to-skin gesture detection according to examples of the disclosure. 
         FIG.  10    illustrates a wearable device in the form of a ring according to examples of the disclosure. 
         FIG.  11    is a system block diagram of a wearable device according to examples of the disclosure. 
         FIG.  12 A  illustrates a hand with an index finger supporting a wearable device (e.g., a ring) but not making contact with a thumb according to examples of the disclosure. 
         FIG.  12 B  illustrates the hand of  FIG.  12 A , except that the index finger is now making contact with the thumb according to examples of the disclosure. 
         FIG.  12 C  illustrates a sense output signal when the index finger and thumb make and break contact as shown in  FIGS.  12 B and  12 A  according to examples of the disclosure. 
         FIG.  13 A  illustrates a hand with an index finger supporting a wearable device (e.g., a ring) but not making contact with a middle finger according to examples of the disclosure. 
         FIG.  13 B  illustrates the hand of  FIG.  13 A , except that the index finger is now making contact with the middle finger according to examples of the disclosure. 
         FIG.  13 C  illustrates a sense output signal when the index finger and middle finger make and break contact as shown in  FIGS.  13 B and  13 A  according to examples of the disclosure. 
         FIG.  14 A  illustrates a hand with an index finger supporting a wearable device (e.g., a ring) and in contact with a middle finger according to examples of the disclosure. 
         FIG.  14 B  illustrates the hand of  FIG.  14 A , except that the thumb is now making contact with the already touching index finger and middle finger according to examples of the disclosure. 
         FIG.  14 C  illustrates a sense output signal when the thumb makes and breaks contact with the already touching index finger and middle finger as shown in  FIGS.  14 B and  14 A  according to examples of the disclosure. 
         FIG.  15 A  illustrates a hand with an index finger supporting a wearable device (e.g., a ring) and making contact with a thumb according to examples of the disclosure. 
         FIG.  15 B  illustrates the hand of  FIG.  15 A , except that the middle finger is now making contact with the already touching index finger and thumb according to examples of the disclosure. 
         FIG.  15 C  illustrates a sense output signal when the middle finger makes and breaks contact with the already touching index finger and thumb as shown in  FIGS.  15 B and  15 A  according to examples of the disclosure. 
         FIG.  16 A  illustrates a hand with an index finger supporting a wearable device (e.g., a ring) and making contact with an opposite hand according to examples of the disclosure. 
         FIG.  16 B  illustrates a left hand with an index finger supporting a wearable device (e.g., a ring) and also a right hand with an index finger supporting another wearable device (e.g., a ring) according to examples of the disclosure. 
         FIG.  16 C  illustrates a hand with an index finger supporting a wearable device (e.g., a ring) and a middle finger supporting another wearable device (e.g., a ring) according to examples of the disclosure. 
         FIG.  17    illustrates a flowchart for detecting input gestures using one or more devices according to examples of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of examples, reference is made to the accompanying drawings which form a part hereof, and in which it is shown by way of illustration specific examples that can be practiced. It is to be understood that other examples can be used and structural changes can be made without departing from the scope of the disclosed examples. 
     This relates to devices and methods of detecting contact between a first body part and a second body part. Sense circuitry can be configured to sense a signal at the sense electrode (e.g., configured to contact the second body part) in response to a drive signal applied to the drive electrode (e.g., configured to contact the first body part). Processing circuitry can be configured to detect contact in accordance with a determination that one or more criteria are met. The one or more criteria can include a first criterion that is met when an amplitude of the sensed signal exceeds an amplitude threshold and a second criterion that is met when the sensed signal has a non-distorted waveform. Using a robust set of criteria, including an evaluation of the quality of the waveform (e.g., whether it is distorted or not), can improve the disambiguation between a skin-to-skin contact event and a proximity event. 
     This also relates to devices and methods of detecting a movement gesture using contact between two fingers of the same hand (e.g., to enable one-handed skin-to-skin input gestures). Sense circuitry can be configured to sense a signal at a sense electrode (e.g., configured to contact a finger of a hand) in response to a drive signal applied to a drive electrode (e.g., configured to contact a different finger of the hand). Processing circuitry can be configured to detect a movement gesture (e.g., a slide gesture) in accordance with a determination that one or more criteria are met. The one or more criteria can include a first criterion indicative of contact between a first finger and a second finger and a second criterion indicative of movement of the first finger along the second finger. 
     This further relates to devices and methods of detecting gestures between a finger of one hand and other body parts (e.g., other fingers or a thumb on the same hand, or the opposing hand) using a single device (e.g., a ring) on the finger of the hand. Sense circuitry in the device can be configured to sense a signal at one or more sense electrodes in the device in response to a drive signal applied to a drive electrode in the device. Processing circuitry can be configured to detect contact or a movement gesture (e.g., a slide gesture) in accordance with a determination that one or more criteria are met. The one or more criteria can include various amplitude criteria, in some instances evaluated over a certain time period. When a particular gesture is detected, an operation can be initiated. 
     This also relates to devices and methods of detecting gestures between a finger of one hand and other body parts (e.g., other fingers or a thumb on the same hand, or the opposing hand) using a device (e.g., a ring) on each of multiple fingers of the same hand, or on fingers of different hands. Sense circuitry in each device can be configured to sense a signal at one or more sense electrodes in the device in response to drive signals applied to a drive electrode in each of the devices. When a particular gesture is detected, an operation can be initiated. 
       FIGS.  1 A- 1 B  illustrate an example system for skin-to-skin contact detection according to examples of the disclosure.  FIG.  1 A  illustrates a system including two wrist-worn wearable devices  150 A,  150 B, each including at least one electrode to establish electrical contact between the wearable device and the wearer&#39;s skin. An electrode of a first wearable device  150 A can be used to drive a drive signal (sometimes referred to as a “stimulation signal”) into the wearer&#39;s body via the electrode&#39;s contact with the wrist of right hand  104 A. An electrode of a second wearable device  150 B can be used to sense a signal (sometimes referred to as a “sensed signal” or “received signal”) from the wearer&#39;s body via contact with the wrist of left hand  104 B. As described herein, without contact between hands  104 A- 104 B, a conductive path through the body can allow for propagation of the drive signal and reception of the sensed signal. Proximity or contact between hands  104 A- 104 B can form a second conductive path through the contact or proximity for propagation of the drive signal and reception of the sensed signal that can change characteristics of the sensed signal. These characteristics can be monitored and analyzed (e.g., by processing circuitry) and used to determine whether skin-to-skin contact has been made as discussed in more detail herein. 
     In some examples, as illustrated in  FIG.  1 A , the wearable devices  150 A- 105 B can be watches (optionally including crown  162  and/or button  164 ) that can each be fastened to a user via strap  154  or any other suitable fastener. One or both of the wearable devices  150 A- 105 B can include a touch screen  152 . It is understood that although wearable devices  150 A- 150 B are illustrated as including a touch screen  152 , that the skin-to-skin contact detection can be achieved without a touch screen or display integrated with wearable devices  150 A- 150 B. Additionally or alternatively, each wearable device can include processing circuitry, drive circuitry sense circuitry, and/or more than one electrode (e.g., to enable the various drive, sense and processing functionalities to be performed by either or both wearable devices). For example,  FIG.  1 B  illustrates a backside of wearable device  150  with two electrodes  166 A-B, though fewer or more electrodes is possible. For example, some devices device can include a single electrode (for single-ended driving and/or sensing capability), two electrodes (e.g., for single-ended driving or sensing and/or for differential driving or sensing), three electrodes (e.g., for single-ended driving and differential sensing and/or for differential driving and single-ended sensing) or four electrodes (e.g., for differential driving and/or differential sensing), etc. It should be understood that each of the watches can include all of the components above, or that the watches may include fewer components or different components. It should be understood that although watches are illustrated in  FIGS.  1 A- 1 B  that different devices are possible and/or different placement of the devices is possible. For example, watches  150 A- 150 B can be replaced with two wristbands; one wristband can include an electrode and drive circuitry and one wristband can include an electrode and sense circuitry. The control of the drive and sense circuitry and/or the processing of the signals received by the sense circuitry can be performed by circuitry within each respective wristband or by circuitry within another device (e.g., a smartphone or other computing device) based on wired or wireless communication between such a device and the wristbands. In some examples, one watch may be used for sensing and processing the sensed signal, and the drive circuitry and electrode can be implemented in another type of device (e.g., a ring). In some examples, one or both devices (e.g., for driving the drive signal and/or sensing the sensed signal) can be implemented in a glove, finger cuff, bracelet, necklace, head-mounted device, necklace, armband, headphones or ear buds. Although primarily described as wearable devices, in some examples, one or both devices can be a non-wearable device such as a handheld controller. Additionally, although primarily described as being implemented in two devices on two hands, it is understood that in some examples that two devices can be implement on one hand (e.g., as illustrated in  FIGS.  7 A- 7 B ), and optionally integrated together in one device (e.g., in a glove). 
       FIG.  2    illustrates a block diagram of an example computing system  200  for skin-to-skin contact detection according to examples of the disclosure. Computing system  200  can include electrodes  202 A- 202 B, sense circuitry  203 , drive circuitry  204  to stimulate first body part with drive signals and measure sensed signals from a second body part. In some examples, the drive circuitry can include a voltage source or (constant) current source to generate the stimulation signal. In some examples, the stimulation signal can have a square waveform. In some examples, the stimulation signal can have a frequency greater than 500 kHz. In some examples, the stimulation signal can be between 1 MHz and 10 Mhz. The drive signal can be applied as a single-ended stimulus via one drive electrode or as a differential signal referenced to a second drive electrode (a floating or ground reference). In some examples, the sense circuitry can include an amplifier (with a feedback network between the input(s) and output(s)). In some examples, the amplifier can be single-ended with the inverting input coupled to the sense electrode and the non-inverting input coupled to a reference electrode (e.g., a ground electrode or a floating electrode). In some examples, the amplifier can be differential with the inverting input coupled to a first sense electrode and the non-inverting input coupled to a second sense electrode. A ground electrode can be coupled between the two sense electrodes. In some examples, the sense circuitry can include multiple amplifiers to sense signals received a multiple sense electrodes (in a single-ended or differential manner). Additionally, computing system  200  can include a digital signal processor (DSP)  206  to analyze and process the sensed signals for skin-to-skin contact detection (and/or gesture detection), and optionally memory  207  to store the data from sense circuitry  203  and/or store configuration data or instructions for DSP  206 . In some examples, computing system  200  can also include host processor  208 , program storage  210  and touch screen  212  (or other display) to perform display or other operations (e.g., in response to skin-to-skin contact). The components of computing system  200  are described in more detail below. 
     Host processor  208  can be connected to program storage  210  to execute instructions stored in program storage  210  (e.g., a non-transitory computer-readable storage medium). Host processor  208  can, for example, provide control and data signals to generate a display image on touch screen  212  (or other display devices), such as a display image of a user interface (UI). Host processor  208  can also receive outputs from DSP  206  (e.g., detection of skin-to-skin contact and/or gestures as touch input) and perform actions based on the outputs (e.g., selection of content or scroll content in a real-world, virtual reality or mixed reality environment, etc.). Host processor  208  can also receive outputs (touch input) from touch screen  212  (or a touch controller, not shown). The input (e.g., touch input from touch screen  212  or skin-to-skin contact/gesture input from DSP  206 ) can be used by computer programs stored in program storage  210  to perform actions. The actions can include, but are not limited to, moving an object such as a cursor or pointer, scrolling or panning, adjusting control settings, opening a file or document, viewing a menu, making a selection, executing instructions, operating a peripheral device connected to the host device, answering a telephone call, placing a telephone call, terminating a telephone call, changing the volume or audio settings, storing information related to telephone communications such as addresses, frequently dialed numbers, received calls, missed calls, logging onto a computer or a computer network, permitting authorized individuals access to restricted areas of the computer or computer network, loading a user profile associated with a user&#39;s preferred arrangement of the computer desktop, permitting access to web content, launching a particular program, encrypting or decoding a message, and/or the like. Host processor  208  can also perform additional functions that may not be related to touch processing and display. 
     Note that one or more of the functions described herein, including the analysis and processing of sensed signals for skin-to-skin contact detection, can be performed by firmware stored in memory  207  and executed by one or more processors (e.g., in DSP  206 ), or stored in program storage  210  and executed by host processor  208 . The firmware can also be stored and/or transported within any non-transitory computer-readable storage medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “non-transitory computer-readable storage medium” can be any medium (excluding signals) that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-readable storage medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device, a portable computer diskette (magnetic), a random access memory (RAM) (magnetic), a read-only memory (ROM) (magnetic), an erasable programmable read-only memory (EPROM) (magnetic), a portable optical disc such a CD, CD-R, CD-RW, DVD, DVD-R, or DVD-RW, or flash memory such as compact flash cards, secured digital cards, USB memory devices, memory sticks, and the like. 
     The firmware can also be propagated within any transport medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “transport medium” can be any medium that can communicate, propagate or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The transport medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic or infrared wired or wireless propagation medium. 
     It is to be understood that the computing system  200  is not limited to the components and configuration of  FIG.  2   , but can include other or additional components (or omit components) in multiple configurations according to various examples. For example, an analog-to-digital converter (ADC) may be included as part of the sense circuitry  203  or between sense circuitry  203  and DSP  206  to convert the signals to the digital domain from the analog domain. As another example, touch screen  212  can be omitted and the input information from the analysis and processing by DSP  206  can be relayed to another device (e.g., a tablet, laptop, smartphone, computer, server, etc.) via wired or wireless connection that can include a display (e.g., a real-world or virtual or mixed reality display). Additionally, the components of computing system  200  can be included within a single device, or duplicated in part or in whole in multiple devices in a system (e.g., as illustrated in and described with reference to  FIG.  1 A ), or can be distributed between multiple devices. In some examples, the drive circuitry  204  and/or sense circuitry  203  can be in separated from the electrodes such that the drive/sense circuitry can be implemented in a device worn on the wrist (or a first part of the body, generally) and the electrodes can be worn on or near the fingers (e.g., as part of devices  708 A- 708 B) or palms (or a second different part of the body, generally). 
     Referring back to sense circuitry  203 , sense circuitry  203  can measure sensed signals and can be in communication with DSP  206  to provide the sensed signals to DSP  206 . In some examples, the sensed signals can be stored in memory  207  (e.g., acting as a data buffer) and the DSP  206  can acquire a buffered sample of the sensed signal waveform for analysis as described herein. In some examples, memory  207  can be implemented as part of DSP  206 . It should be understood that although a DSP is described, other processing circuits could be used to implement the analysis and processing described herein including a microprocessor, central processing unit (CPU), programmable logic device (PLD), and/or the like. 
       FIGS.  3 A- 3 B  illustrate a proximity and a contact, respectively, between a first body part and a second body part according to examples of the disclosure.  FIGS.  4 A- 4 B  illustrate time domain representations  400 ,  420  and frequency domain representations  402 ,  422  of the sensed signal corresponding to the proximity or the contact according to examples of the disclosure. With or without contact or proximity, the stimulation generated by wearable device  308 A (e.g., corresponding to wearable device  150 , drive circuitry  204  and electrode  202 A) can propagate through the body via a first path  309 A, and can be received by wearable device  308 B (e.g., corresponding to wearable device  150 , sense circuitry  203  and electrode  202 B). A second path  309 B can be formed between wearable devices  308 A- 308 B due to contact or proximity between index finger  304  and/or right hand  302  and left hand  306 . The second path  309 B can cause changes to the sensed signal when contact or proximity between index finger  304  and left hand  306  occurs compared with the expected sensed signal from first path  309 A.  FIG.  3 A  illustrates that a second path  309 B can be formed between index finger  304  of right hand  302  in proximity to the palm of left hand  306  (e.g., a capacitive path).  FIG.  3 B  illustrates that a second path  309 B can be formed between index finger  304  of right hand  302  in contact with the palm of left hand  306 . The differences in the sensed waveform can be used to distinguish between skin-to-skin touch and skin-to-skin proximity. 
     In particular, as shown in  FIGS.  4 A- 4 B , the amplitude of a frequency domain peak (e.g., peak  404  in  FIG.  4 A  and peak  424  in  FIG.  4 B ) can increase relative to reference peak  414  due to proximity or contact. Thus, an amplitude criterion can be used to detect skin-to-skin contact or proximity. For example, when the peak  404 ,  424  exceeds a threshold  406 ,  426 , the processing circuitry (e.g., DSP  206 ) can detect contact or proximity. When peak  404 ,  424  is below the threshold  406 ,  426 , the processing circuitry (e.g., DSP  206 ) can detect an absence of contact or proximity. In some examples, threshold  406  and threshold  426  illustrated in  FIGS.  4 A- 4 B  can be the same threshold, and one or more additional criteria can be used to differentiate between a touch event and a proximity event, as described in more detail below. Although shown as frequency domain thresholds, it should be understood that time domain thresholds can be used instead for time domain representations  400 ,  420 , in some examples. In some examples, thresholds  406  and  426  can be different thresholds, and can be used to differentiate between a touch event and a proximity event. For example, the relative amplitude increase of peak  404  corresponding to a proximity event can be less than the amplitude increase of peak  424  corresponding to a touch event. A first, higher threshold can be set to detect a touch event, and a second, lower threshold can be set to detect a proximity event (e.g., when the amplitude is less than the first threshold but above the second threshold). 
     Relying on an amplitude criterion alone for differentiation between a touch and hover, however, may be inaccurate (false detection of touch and/or proximity events) because the amplitude may be a function of more than the distance between the two body parts (the difference between touch versus proximity). For example, the capacitive nature of the second path  309 B for a proximity event (without contact) can result in amplitude changes in the sensed signal that can be a function of the distance between two body parts (e.g., a distance between left hand  306  and index finger  304 /right hand  302 ) and also the size of the body parts (e.g., the size of finger  304  as compared with the hand  302 ). Likewise, the second path  309 B for a contact event can see amplitude changes based on the size contact, which can change based on the amount of force applied or the number of fingers making contact, for example. As a result, the approach of index finger  304  of right hand  302  and the proximity of right hand  302  and left hand  306  can result in an amplitude spike indicative of contact based on the amplitude threshold before index finger  304  makes contact with left hand  306 . This can cause a false detection of contact (e.g., detecting contact while the finger hovers), and even if contact occurs subsequently, the amplitude spike can mask the contact of index finger  304  (because the subsequent amplitude change may be a relatively small change compared with the proximity of the larger hands). Additionally, the timing of the moment of contact (even if it can be differentiated from proximity) may be imprecise. 
     As described herein, one or more additional criteria can be used to improve skin-to-skin contact or proximity detection. The one or more additional criteria can be related to other characteristics of the sensed signal. In some examples, the one or more additional criteria can correspond to whether the sensed signal has a distorted waveform or not. For example, time domain representation  400  corresponding to a proximity event can include distortion compared with the time domain representation corresponding to a touch event. The waveform can appear more similar to a saw-tooth waveform (distorted in  FIG.  4 A ) than a sine waveform (non-distorted in  FIG.  4 B ). 
     In some examples, the sensed signal can be correlated with a reference waveform. For example, a reference waveform can be a sine waveform corresponding to the sensed signal without contact or proximity events. For example,  FIG.  5    illustrates a block diagram of a correlation circuit  500  according to examples of the disclosure. Correlator  502  of correlation circuit  500  can receive the sensed signal as a first input and a reference signal as a second signal, and can output a correlation of the input signals. The sensed signal can be provided by sense circuitry  203  directly or from storage in memory  207 , for example. The reference signal can be stored in memory  207 . Correlator  502  can be implemented, in some examples, in DSP  206 . When the correlation is high (above a threshold) between the sensed signal and the reference waveform, the processing circuitry (e.g., DSP  206 ) can determine that the signal has a non-distorted waveform and/or detect a skin-to-skin contact event. When the correlation is low (below the threshold) between the sensed signal and the reference waveform, the processing circuitry (e.g., DSP  206 ) can determine that the signal has a distorted waveform and/or detect a proximity event (without contact). In some examples, the reference waveform can be a saw-tooth waveform, and the conventions can be reversed with respect to the threshold (e.g., high correlation corresponds to distortion/proximity and low correlation corresponds to contact). It should be understood that the sensed signal and reference signal waveforms illustrated correspond to a square wave stimulation applied to the body. However, a different stimulation signal, sensed signal, and reference signal can be used in other examples. Although described as a correlation of the time domain representations, correlation can also be performed on frequency domain representations. 
     In some examples, a second criterion can be based on the width of a frequency domain peak. The width of the peak  404 ,  424  (W 1 , W 2  respectively) in the frequency domain can provide an indication of distortion. For example, a frequency domain representation of a pure sine wave at one frequency can be spike at that frequency. The narrower the width of the peak, the closer the sensed signal is to a sine wave. Thus, a width threshold can be used to determine whether the sensed signal is distorted or non-distorted based on how the width of the peak compares with the width threshold. When the width of peak  404 ,  424  is below the threshold, the processing circuitry (e.g., DSP  206 ) can determine that the signal has a non-distorted waveform and/or detect a skin-to-skin contact event. When the width of peak  404 ,  424  is above the threshold, the processing circuitry (e.g., DSP  206 ) can determine that the signal has a distorted waveform and/or detect a proximity event (without contact). 
     In some examples, the width of the peak can be measured at a fixed point (e.g., at a fixed amplitude point). For example, the width can be measured at the amplitude threshold  406 ,  426 , or at another fixed point. In some examples, the width measurement can be normalized according to the amplitude of the peak (because peaks may widen as the amplitude increases). The amplitude-normalized width of the peak can be used with the amplitude-normalized width threshold in a similar manner as described above. In some examples, the width can be measured at a midpoint of the amplitude of the peak. In some examples, the amplitude-normalized width can be a ratio of the width at a fixed amplitude point to the maximum amplitude at the peak (e.g., scaled according to maximum amplitude) that can be compared to an amplitude-normalized width threshold. 
     In some examples, a second criterion can be based on an envelope of the sensed signal. As illustrated in  FIG.  4 A , time domain representation  400  of the sensed signal includes an envelope  401  when a proximity event occurs, whereas as illustrated in  FIG.  4 B  the envelope can be essentially flattened when a contact event occurs. In some examples, the envelope can appear as a second, low-frequency peak  408  (relative to peak  404 ) in the frequency domain representation  402 . When the amplitude of the second peak  408  is above a second amplitude threshold  412  (different and lower than amplitude threshold  406 ), the processing circuitry (e.g., DSP  206 ) can determine that the signal has a distorted waveform and/or detect a proximity event (without contact). When the second peak  408  is below threshold  412  (or non-existent), the processing circuitry (e.g., DSP  206 ) can determine that the signal has a non-distorted waveform and/or detect a skin-to-skin contact event. Although described as frequency domain processing to identify the existence of the envelope in a beat frequency, alternatively processing can be performed in the time domain using the time domain representation of the envelope with a threshold based on the flatness of the envelope function. 
     In some examples, the second criterion can be based on a phase shift between the stimulation signal and the sensed signal. For example, in addition to receiving the sensed signal, the processing circuitry (e.g., DSP  206 ) can also receive the drive signal. The processing circuitry can calculate the phase shift. Thus, a phase shift threshold can be used to determine whether the sensed signal is distorted or non-distorted based on how the calculated phase shift compares with the phase shift threshold. In some examples, when the phase shift is below the threshold, the processing circuitry (e.g., DSP  206 ) can determine that the signal has a non-distorted waveform and/or detect a skin-to-skin contact event. When the phase shift is above the threshold, the processing circuitry (e.g., DSP  206 ) can determine that the signal has a distorted waveform and/or detect a proximity event (without contact). 
     In some examples, the one or more criteria can include a third criterion. For example, when hands are within the field of view of a camera or cameras (not shown in  FIG.  2   ), processing circuitry can receive an input stream from the camera(s) and can estimate whether a contact or proximity event occurs using the camera input. In some examples, the camera may provide useful information about the size, position and orientation of the body parts, which may used to differentiate between an amplitude spike caused by large objects in proximity (e.g., two parallel palms) versus contact between two smaller objects (e.g., two finger tips). However, it is understood that the detection of and differentiation between skin-to-skin contact events and proximity events can be performed even without the use of a camera. Detection without the camera(s) may be particularly advantageous when one or both hands are out of the field of view of the camera(s) or one of the hands occludes the other of the hands (making optical detection of whether objects are touching or in proximity difficult). 
       FIG.  6    illustrates an example process  600  of skin-to-skin contact detection according to examples of the disclosure. At  605 , a sensed signal can be measured at a sense electrode (e.g., in contact with a first body part) in response to a drive signal applied by a drive electrode (e.g., in contact with a second body part, different from the first body part). In some examples, the drive signal can be a square wave with a frequency greater than 500 kHz. In some examples, the drive signal can be a square wave with a frequency between 1 MHz and 10 MHz. The sensed signal can be processed to detect skin-to-skin contact between two body parts. In some examples, the processing can include transforming the sensed signal from a time domain to a frequency domain (e.g., using a fast Fourier transform (FFT) or other suitable technique). In some examples, the processing can be performed entirely in the time domain without transforming the sensed signal to the frequency domain. The processing can include, at  610 , detecting contact between the first body part and the second body part in accordance with a determination that one or more criteria are met. The one or more criteria can include a first criterion that is met when an amplitude of the sensed signal exceeds an amplitude threshold ( 615 ). For example, determining whether the amplitude of the sensed signal exceeds the amplitude threshold for evaluating the first criterion can include comparing a peak identified in the frequency domain with the amplitude threshold ( 620 ). The one or more criteria can include a second criterion that is met when the sensed signal has a non-distorted waveform ( 625 ). Evaluating the second criterion can include, in some examples, comparing a width (in some examples an amplitude-normalized width) of the peak identified in the frequency domain with a width threshold ( 630 ). In accordance with a determination that the width is below the width threshold, determining that the sensed signal has the non-distorted waveform (the second criterion is met); and in accordance with a determination that the width is above the width threshold, determining that the sensed signal has a distorted waveform (the second criterion is not met). Evaluating the second criterion can include, in some examples, comparing a second, low-frequency peak identified in the frequency domain with a second amplitude threshold ( 635 ). In accordance with a determination that an amplitude of the second peak is below the second amplitude threshold (or in the absence of a second peak at the lower frequency), the processing circuitry can determine that the sensed signal has the non-distorted waveform (the second criterion is met). In accordance with a determination that the amplitude of the second peak is above the second amplitude threshold, the processing circuitry can determine that the sensed signal has a distorted waveform (the second criterion is not met). Evaluating the second criterion can include, in some examples, correlating the sensed signal with a reference signal ( 640 ). In accordance with a determination that the correlation is above a correlation threshold, determining that the sensed signal has the non-distorted waveform (the second criterion is met); and in accordance with a determination that the correlation is below the correlation threshold, determining that the sensed signal has a distorted waveform (the second criterion is not met). Process  600  can include, at  645 , detecting no contact between the first body part and the second body part in accordance with a determination that the one or more criteria are not met. Process  600  can include, at  650 , detecting a proximity without contact between the first body part and the second body part in accordance with a determination that first criterion is met and that the second criterion is not met. 
     It is understood that process  600  is an example process and that some of the processing mentioned above can be omitted or different processing may be performed. For example, the second criterion can be evaluated using processing of  630 ,  635  or  640 . In some examples, the second criterion can met when multiple characteristics indicate non-distortion of the waveform (e.g., using processing of  630 ,  635  and/or  640 ). 
     In some examples, in addition to detecting skin-to-skin contact, skin-to-skin gestures can be detected as well. For example, the gestures enabled by skin-to-skin contact can include a tap, double tap, tap-and-hold (long press) and the like. In additional, other skin-to-skin contact gestures can be enabled based on movement subsequent to contact. For example, a sliding gesture can be detected based on skin-to-skin contact followed on-skin movement (e.g., prior to breaking skin-to-skin contact). In some examples, the skin-to-skin contact can be between two fingers on the same hand and the sliding gesture can be one finger sliding along a second finger on the same hand. 
       FIGS.  7 A- 7 B  illustrate an example system for detection of a skin-to-skin gesture according to examples of the disclosure. In particular,  FIGS.  7 A- 7 B  illustrate a slide gesture between a first finger and a second finger of the same hand according to examples of the disclosure. The system can use a computing system including the same or similar components as described with reference to computing system  200 .  FIGS.  8 A- 8 C  illustrate time domain representations  800 ,  810  and  820  and frequency domain representations  802 ,  812 ,  822  of the sensed signal corresponding to a finger-to-finger slide gesture according to examples of the disclosure. As illustrated in  FIGS.  7 A- 7 B , a first wearable device  708 A (e.g., corresponding to wearable device  150 , drive circuitry  204  and electrode  202 A) can be coupled on a first finger, thumb  702 , and a second wearable device  708 B (e.g., corresponding to wearable device  150 , sense circuitry  203  and electrode  202 B) can be coupled on a second finger, index finger  704 . In some examples, the first wearable device  708 A can be disposed at or near (within a threshold distance of) the midpoint of thumb  702  (e.g., at or near the boundary between the distal bone and the proximal bone). In some examples, the first wearable device  708 A can be disposed at or near (within a threshold distance of) the base of thumb  702  (e.g., at or near the base of the metacarpal bone). In some examples, the second wearable device  708 B can be disposed at or near (within a threshold distance of) the base of index finger  704  (e.g., at or near the base of the metacarpal bone). In some examples, the first wearable device  708 A can be finger cuff and the second wearable device  708 B can be a ring. In some examples, the first and second wearable devices can be implemented as part of a glove. 
     With or without the contact between thumb  702  and index finger  704  shown in  FIGS.  7 A- 7 B , the stimulation generated by wearable device  708 A can propagate through the body via a first path  709 A, and can be received by wearable device  708 B. A second path  709 B can be formed between wearable devices  708 A- 708 B due to contact between thumb  702  and index finger  704 . The second path  709 B can cause changes to the sensed signal compared with the expected sensed signal from first path  709 A when contact between thumb  702  and index finger  704  occurs. The changes to the sensed signal can be different depending upon the location of thumb  702  on index finger  704 . In particular, the closer the tip of thumb  702  is to the tip of index finger  704 , the higher the resistance of the second path and the lower the resulting amplitude spike due to contact. In a similar manner, the closer the tip of thumb  702  is to the base of index finger  704  (and wearable device  708 B), the lower the resistance of the second path and the larger the resulting amplitude spike due to contact. The changes in the sensed waveform (e.g., the difference in amplitude spike) can be used to identify movement of the contact location between the two fingers to identify a gesture (e.g., a slide gesture). 
     The detection of a movement gesture can include the detection of contact between the first finger and the second finger (e.g., thumb  702  and index finger  704 ) and the detection of movement of the first finger along the second finger. The skin-to-skin contact of thumb  702  and index finger  704  can be detected via the one or more criteria (e.g., including an amplitude criterion and a non-distortion criterion) as discussed above and not repeated here for brevity. The movement of the contact can be detected by an increase or decrease in amplitude of the sensed signal (relative to the initial amplitude at contact) while skin-to-skin contact is maintained. 
       FIG.  8 A , for example, shows a frequency domain peak  806  corresponding to an initial contact (e.g., corresponding to the position of the fingers shown in  FIG.  7 A ).  FIGS.  8 B and  8 C  show the corresponding frequency domain peaks corresponding to a subsequent contact.  FIG.  8 B , for example, shows a frequency domain peak  816  corresponding to a subsequent contact with a decreased amplitude peak indicative of movement away from the base of the finger (e.g., away from wearable device  708 B).  FIG.  8 C , for example, shows a frequency domain peak  826  corresponding to a subsequent contact with an increased amplitude peak, indicative of movement toward the base of the finger (e.g., toward from wearable device  708 B, corresponding to the position of the fingers shown in  FIG.  7 B ). Detection of movement away from the base of the finger can correspond to a slide-away gesture, and detection of movement toward the base of the finger can correspond to a slide-toward gesture. The slide-away and slide-toward gestures can provide different inputs to a system. In some examples, the opposite directions of the slide inputs can correspond to opposite functionality (e.g., raising vs. lowering volume, moving a slider control in opposite directions, etc.). Although shown as frequency domain peaks, it should be understood that changes of amplitude in the time domain can be used instead for detection of movement and determining a direction of sliding. 
     In some examples, in order to detect a slide gesture, the amount of movement must be a threshold amount of movement in order to avoid false positives when a change in amplitude detected may due to other reasons other than a change in position (e.g., movement). For example, the other reasons may include a change in the size of the contact (e.g., by adding/removing fingers, pressing with more/less force with the finger, or changing the orientation of the finger) or adding moisture. Additionally or alternatively to requiring a threshold amount of movement to identify a movement gesture, in some examples, information from another sensor can be used to exclude these external causes. For example, camera(s) or other optical sensor(s), a force sensor or moisture sensor can be used to exclude other causes of the change in the amplitude of the finger. For example, camera(s)/optical sensor(s) can be used to exclude the change in number of fingers or the orientation or force of the finger. A force sensor can be used to exclude the change in applied force. A moisture sensor can be used to exclude a change in moisture. 
     Additionally or alternatively, in some examples, one or more additional sense electrodes and corresponding sense circuitry can be used to record multiple measurements along a finger (e.g., along index finger  704 ). For example, an additional sense electrode and/or sense circuitry can be located at or near the distal bone of index finger  704  in addition to the electrode and/or sense circuitry at or near the base of the metacarpal bone of index finger  704 . In some examples, the slide of thumb  702  can be detected based on both the increase in the sensed signal at one sense electrode and the decrease in the sensed signal at the other sense electrode (or visa versa). In some examples, a differential measurement of the signal sensed from the two sense electrodes can be taken and the increase or decrease in the differential sensed signal can be used to detect a slide gesture. Such a differential measurement can improve rejection of alternative sources of signal amplitude change that may be common mode. For example, the change in amplitude due to applied force can appear as common mode at both sense electrodes and thus may be removed by a differential measurement (thereby reducing false positive detection of force as a gesture). It is understood that the differential measurement can provide a similar benefit to reducing false positives in skin-to-skin contact detection as described herein (e.g., not limited to reducing false positives for gesture detection). 
     Although movement gestures are described herein primarily with respect to finger-to-finger gestures, it should be understood that gestures may be detected using other body parts. For example, using the wearable devices of  FIGS.  3 A- 3 B , a sliding gesture may be detected of one finger on one hand sliding along a second finger of the other hand. Additionally or alternatively, a sliding gesture may be detected of one finger along a palm of the other hand. In some examples, multiple sense electrodes (and corresponding sensing circuitry) can be located at different parts of the palm. For example, as shown in  FIG.  3 B , four sensing electrodes  350 A- 350 D can be disposed at approximately four corners of the palm (e.g., in a glove for example) and can be sensed with corresponding sensing circuitry (e.g., co-located or located elsewhere, such as on the backside of the palm or in wearable device  308 B). Based on the relative changes in amplitude at the multiple sense electrodes, the processing circuitry can determine relative movement of the index finger  304 . As a result, multiple directional slide gestures can be enabled (e.g., slide up, slide down, slide left, slide right, diagonal slides, etc.). The sensed signals may be differential between sense electrodes to reduce common mode changes to signal amplitude due to applied force as described above. 
       FIG.  9    illustrates an example process  900  of skin-to-skin gesture detection according to examples of the disclosure. At  905 , a sensed signal can be measured at a sense electrode (e.g., in contact with a finger of a hand) in response to a drive signal applied by a drive electrode (e.g., in contact with a different finger of the same hand). In some examples, the drive signal can be a square wave with a frequency greater than 500 kHz. In some examples, the drive signal can be a square wave with a frequency between 1 MHz and 10 MHz. At  910 , the sensed signal can be processed to detect a skin-to-skin contact gesture in accordance with a determination that one or more criteria are met. In some examples, the processing can include, at  915 , detecting skin-to-skin contact between the two fingers in accordance with a determination that one or more contact criteria are met (e.g., as described above with respect to process  900 , and not repeated here for brevity). The processing can include, at  920 , detecting movement of a first finger along a second finger. Detecting movement of the first finger along the second finger can be based on an increase or decrease in amplitude of the sensed signal subsequent to and while contact is made between the first and second fingers ( 925 ). In some examples, the increase or decrease in amplitude (relative to the initial amplitude upon contact) can be based on the time domain sensed signal. In some examples, the increase or decrease in amplitude can be based on the frequency domain sensed signal (e.g., such that the processing may include a frequency domain transformation). An increase in amplitude from an initial amplitude upon contact can be indicative of a slide-toward gesture. A decrease in amplitude from the initial amplitude upon contact can be indicative of a slide-away gesture. In some examples, to reduce false positive detection of a gesture, that a threshold amount of increase or decrease in amplitude may be required (corresponding to a threshold amount of movement) to detect a gesture. In some examples, to reduce false positive detection of a gesture, an additional sensor may be used to exclude another source of the increase or decrease (e.g., a camera, force sensor, etc.). At  930 , in accordance with a determination that the one or more criteria are not met, the processing circuitry (e.g., DSP  206 ) can forgo detecting the movement gesture. It is understood that process  900  is an example and that some of the processing mentioned above can be omitted or different processing may be performed. 
     Although examples of the disclosure presented above utilize at least two separate devices, including one device to generate a drive signal and another device to receive a sense signal, in other examples a single device (e.g., a ring) can be used to both generate a drive signal and receive a sense signal to detect contact and/or movement gestures between a finger of one hand and other body parts (e.g., other fingers or a thumb on the same hand, or the opposing hand). For example, a single device can detect a same-hand index finger and thumb touch (pinch or tap), an index finger and middle finger touch (pinch or tap), an index finger and middle finger touch followed by the addition of the thumb, an index finger and thumb touch followed by the addition of the middle finger, an index finger touching or tapping an opposite hand, or the thumb sliding along the index finger, and other gesture inputs. These gesture inputs can be detected and advantageously used to initiate operations using a single unobtrusive device, such as a ring, that may be commonly worn by a user for AR/VR and smart home operations. In still other examples, multiple devices, each capable of generating a different stimulation frequency and receiving a sense signal, can be utilized to unambiguously detect a finger touching an opposite hand, detect finger pinches using the thumb and multiple fingers of the same hand performed at different times or simultaneously, or detect gestures performed on two hands at different times or simultaneously. 
       FIG.  10    illustrates wearable device  1002  in the form of a ring according to examples of the disclosure. In the example of  FIG.  10   , wearable device  1002  can include band mechanism  1018  electrically coupled to electronic jewel system (jewel)  1020 , although in other examples the jewel may be integrated within the band mechanism. Band mechanism  1018  can include ground electrode  1008 , drive electrode  1010 , and differential sense electrodes  1012  and  1014 . In some examples, these electrodes can be wrapped fully or almost entirely around the circumference of band mechanism  1018 . In other examples, the electrodes can be discrete electrode patches. 
       FIG.  11    is a system block diagram of wearable device  1102  according to examples of the disclosure. In the example of  FIG.  11   , which may correspond to device  1002  in  FIG.  10   , band mechanism  1118  can be electrically coupled to jewel  1120  through connections  1122 , which in some examples can be so-called “pogo pins,” which are spring-loaded electrical connectors that press into, and make electrical contact with, conductive areas (lands or targets). Band mechanism  1118  can include ground electrode  1108 , drive electrode  1110 , and sense electrodes  1112  and  1114 . 
     Jewel  1120  can include controller  1124  coupled to memory and/or storage  1126 . Controller  1124  may correspond to DSP  206  described above and shown in  FIG.  2   , and can include one or more processors capable of executing programs stored in memory  1126  to perform various functions. In some examples of the disclosure, controller  1124  can be connected to wireless transmitter or transceiver  1128  and one or more of inertial measurement unit (IMU)  1130  and haptics generator  1168 . Memory  1126  may correspond to memory  207  and/or program storage  210  described above and shown in  FIG.  2   , and can include, but is not limited to, random access memory (RAM) or other types of memory or storage, watchdog timers and the like. In some examples, controller  1124  can include drive circuitry  1132  configured for applying a stimulation signal to drive electrode  1110 , and/or sense circuitry  1134  configured for sensing signals on sense electrodes  1112  and  1114 . Drive circuitry  1132  and sense circuitry  1134  may correspond to drive circuitry  204  and sense circuitry  203  described above and shown in  FIG.  2   , respectively. In some examples, drive circuitry  1132  can be separate from controller  1124  include a frequency source or generator, an amplifier, a pulse-width modulator (PWM) or the like for generating a stimulation signal. In some examples, the stimulation signal can be in the range of about 100 kHz to 10 MHz, because higher frequencies can pass more easily through the capacitive nature of a user&#39;s body. In some examples, the stimulation signal can be in the range of 3.3V, which can be advantageously provided directly from some microcontrollers without the need for level shifters. In some examples, sense circuitry  1134  can be separate from controller  1124 , and can include an instrumentation amplifier that can perform differential sensing across two inputs, each coupled to a different sense electrode  1112  and  1114 . In some examples, sensing can be performed at about 5 megasamples per second (MS/s). Controller  1124  can also be communicatively coupled to IMU  1130  to process signals from the IMU to determine parameters such as the angular rate, orientation, position, and velocity of wearable device  1102 . In some examples, controller  1124  can be communicatively coupled to haptics generator  1168  to initiate haptic feedback. Controller  1124  can also be communicatively coupled to wireless transmitter or transceiver  1128  to wirelessly send and receive data and other information. In some examples, wireless transmitter or transceiver  1128  can communicate wirelessly with desktop, laptop and tablet computing devices, smartphones, media players, other wearables such as watches and health monitoring devices, smart home control and entertainment devices, headphones and ear buds, and devices for computer-generated environments such as augmented reality, mixed reality, or virtual reality environments, and the like. 
     It should be apparent that the architecture shown in  FIG.  11    is only one example architecture of band mechanism  1118  and jewel  1120 , and that the system could have more or fewer components than shown, or a different configuration of components. For example, some of the processing of jewel  1120  can be offloaded to separate devices such as those mentioned above, and the jewel can contain reduced controller functionality along with wireless transceiver  1128  to enable communication with those separate devices. Regardless of where they are located, the various components shown in  FIG.  11    can be implemented in hardware, software, firmware or any combination thereof, including one or more signal processing and/or application specific integrated circuits. 
       FIG.  12 A  illustrates hand  1200  with index finger  1204  supporting wearable device (e.g., ring)  1202  but not making contact with thumb  1206  according to examples of the disclosure. Although the example of  FIG.  12 A  shows device  1202  worn over index finger  1204 , it should be understood that in other examples device  1202  can be worn over other fingers such as middle finger  1216 , or over thumb  1206 . Device  1202  can include ground electrode  1208 , drive electrode  1210 , differential sense electrodes  1212  and  1214 , and other electronics not shown in  FIG.  12 A . The order of ground electrode  1208 , drive electrode  1210 , and differential sense electrodes  1212  and  1214  need not be as shown in the example of  FIG.  12 A , and in other examples the order of electrodes can be rearranged. In addition, in other examples a single-ended sense electrode can be utilized instead of differential sense electrodes  1212  and  1214 . 
       FIG.  12 B  illustrates the hand of  FIG.  12 A , except that index finger  1204  is now making contact with thumb  1206  according to examples of the disclosure. 
       FIG.  12 C  illustrates sense output signal  1236  detected at device  1202  when index finger  1204  and thumb  1206  make and break contact as shown in  FIGS.  12 B and  12 A  according to examples of the disclosure. In the example of  FIG.  12 C , sense output signal  1236  can be derived from an output of an instrumentation amplifier or other circuitry in device  1202 . For example, raw differential sense signals can be received at sense electrodes  1212  and  1214 , and sense output signal  1236  can be a selected peak of a Fast Fourier Transform (FFT) of the raw differential sense signals over time. In other examples, as an alternative to the FFT signal processing described above, an envelope of the raw differential signals can be captured over time. The amplitude modulated (AM) raw differential sense signals can be high-pass or band-pass filtered using a filter tuned to the stimulation signal frequency to remove RF frequencies that can distort the envelope. The filtered signals can then be rectified (e.g., using a rectifier circuit) and passed through an envelope detector (e.g., using an envelope detector circuit) to produce output signal  1236  without RF components. If multiple stimulation signal frequencies are employed, tuned filters, rectification and envelope detection can be separately performed at each frequency. Sense output signal  1236  can represent a “signature” of index finger  1204  coming into contact with thumb  1206 , and therefore detection of this signature can enable device  1202  to determine that an input gesture comprised of an index finger and thumb pinch has been received. 
     At time t 1 , index finger  1204  and thumb  1206  are not touching (the “break contact” condition as shown in  FIG.  12 A ), and a stimulation signal generated at drive electrode  1210  can propagate through index finger  1204  to differential sense electrodes  1212  and  1214 , producing voltage v 1  on sense output signal  1236 . At time t 2 , index finger  1204  and thumb  1206  contact each other (the “make contact” condition as shown in  FIG.  12 B ), which can provide grounding path  1238  between sense electrode  1214  and ground electrode  1208  through the thumb. Grounding path  1238  can result in a greater voltage difference between differential sense electrodes  1212  and  1214 , which can cause a resultant drop in the amplitude of sense output signal  1236  to v 2 . It should be noted that if thumb  1206  does not contact index finger  1204  but instead contacts the middle, ring or pinky fingers, grounding path  1238  would not exist and no voltage drop to v 2  would occur. At time t 4 , index finger  1204  and thumb  1206  separate (break contact), and because grounding path  1238  is no longer present, sense output signal  1236  returns to v 1 . 
     In some examples, circuitry within device  1202  (e.g., an analog-to-digital converter (ADC) or other circuitry) can be used to capture voltage levels and determine when the sense output is above, below or within various voltage thresholds, such as above voltage threshold vth 1  or below voltage threshold vth 2 . However, because voltage levels by themselves may not be sufficient to unambiguously identify a signature and determine that a particular gesture has occurred, in some examples time durations can also be monitored. Time durations can be determined and monitored using timing circuits and/or algorithms within device  1102  to evaluate signal transition times, shapes, durations, etc. For example, at time periods t 2  and t 4 , sense output signal  1236  can be evaluated to confirm that it transitions between expected voltage levels or crosses expected voltage thresholds within a certain time period (i.e., to detect expected steep transitions in the sense output signal as compared to gradual increases or decreases indicative of other behavior). 
     In the example of  FIG.  12 C , when sense output signal  1236  is determined to be above vth 1  at time t 1 , a timer can be started (e.g., clock cycles can be counted, a capacitance can be charged, etc.) to confirm that the sense output signal remains above vth 1  for a first time period (e.g., until time t 2 ), which can indicate a steady state “break” condition where index finger  1204  is not touching any other finger or thumb. At time t 2 , when sense output signal  1236  drops from v 1  to v 2 , it can be determined whether the sense output signal has fallen with a requisite steepness. When the voltage level is confirmed to have dropped below vth 2  with a requisite steepness, it can then be determined how long the sense output signal stays below voltage threshold vth 2 . In one example, when the sense output signal falls below voltage threshold vth 2  with a certain steepness and stays below voltage threshold vth 2  for a second time period until at least time t 3 , it can be determined that an index finger  1204  and thumb  1206  contact (e.g., an index finger-thumb pinch) has occurred. When sense output signal  1236  returns to a voltage level above voltage threshold vth 1  at time t 4  with a requisite steepness and stays at that level for a third time period (e.g., to time t 5 ), it can be determined that index finger  1204  and thumb  1206  have separated and returned to the steady state condition. 
     In some examples, the single device  1202  can be utilized to detect a slide gesture. For example, if thumb  1206  contacts index finger  1204  near the tip of the index finger, a certain voltage drop at sense output signal  1236  can be produced (e.g., a voltage drop to a level below vth 2 ). However, if thumb  1206  contacts index finger at a location closer to device  1202 , a reduced voltage drop can be produced on sense output signal  1236  (but still below vth 2  in the example of  FIG.  12 C ). Thus, for example, if thumb  1206  initially touches the tip of index finger  1204 , then slides along the index finger towards device  1202 , the voltage at sense output signal  1236  may initially be at v 2 , but increase towards vth 2  as the thumb slides towards the device. In some examples, different voltages at sense output signal  1236  can be mapped to different locations along index finger  1204 , or voltage changes at the sense output can be converted to relative slide distances. In other examples, capturing the voltage level of sense output signal  1236  over time can allow for a determination of slide velocity or acceleration. These slide detection parameters can be used as control inputs for various operations. 
     Although  FIG.  12 C  illustrates a voltage drop when index finger  1204  contacts thumb  1206 , in other examples the amplitude of sense output signal  1236  may rise when the index finger contacts the thumb. In general, for the example of  FIG.  12 C  and any of the subsequently disclosed examples, the direction and amount of change in the sense output signal for a given gesture can be a function of the order in which the sense electrodes are arranged, and/or the configuration of the sense circuit within the device. Thus, it should be understood that the voltage levels and the direction of voltage changes described and illustrated herein are for purposes of illustration only, and that in other examples the voltage levels can be different, and signals can be “inverted.” Accordingly, for example, a voltage above first voltage threshold vth 1  can be said to “satisfy” that threshold in  FIG.  12 C , but if  FIG.  12 C  were inverted due to a different circuit configuration, a voltage below vth 1  can also be said to “satisfy” that threshold. 
       FIG.  13 A  illustrates hand  1300  with index finger  1304  supporting wearable device (e.g., ring)  1302  but not making contact with middle finger  1316  according to examples of the disclosure. Device  1302  can include ground electrode  1308 , drive electrode  1310 , differential sense electrodes  1312  and  1314 , and other electronics not shown in  FIG.  13 A . The order of ground electrode  1308 , drive electrode  1310 , and differential sense electrodes  1312  and  1314  need not be as shown in the example of  FIG.  13 A , and in other examples the order of electrodes can be rearranged. In addition, in other examples a single-ended sense electrode can be utilized instead of differential sense electrodes  1312  and  1314 . 
       FIG.  13 B  illustrates the hand of  FIG.  13 A , except that index finger  1304  is now making contact with middle finger  1316  according to examples of the disclosure. 
       FIG.  13 C  illustrates sense output signal  1344  detected at device  1302  when index finger  1304  and middle finger  1316  make and break contact as shown in  FIGS.  13 B and  13 A  according to examples of the disclosure. In the example of  FIG.  13 C , sense output signal  1344  can be derived from an output of an instrumentation amplifier or other circuitry in device  1302 . For example, raw differential sense signals can be received at sense electrodes  1312  and  1314 , and sense output signal  1344  can be a selected peak of an FFT of the raw differential sense signals over time. Alternatively, filtering, rectification and envelope detection as described above can also be used to generate sense output signal  1344 . Sense output signal  1344  can represent a “signature” of index finger  1304  coming into contact with middle finger  1316 , and therefore detection of this signature can enable device  1302  to determine that an input gesture comprised of an index finger coming into contact with a middle finger has been received. 
     At time t 1 , index finger  1304  and middle finger  1316  are not touching (the “break contact” condition as shown in  FIG.  13 A ), and a stimulation signal generated at drive electrode  1310  can propagate through index finger  1304  to differential sense electrodes  1312  and  1314 , producing voltage v 1  on sense output signal  1344 . At time t 2 , index finger  1304  and middle finger  1316  contact each other (the “make contact” condition as shown in  FIG.  13 B ), which can provide grounding path  1340  between sense electrode  1314  and ground electrode  1308  through the middle finger. Grounding path  1340  can result in a greater voltage difference between differential sense electrodes  1312  and  1314 , which can cause a resultant drop in the amplitude of sense output signal  1344  to v 2 . After time t 2 , sense output signal  1344  can gradually increase over time in what can appear to be a roughly logarithmic curve until time t 4 , when index finger  1304  and middle finger  1316  separate (break contact). In some examples, this gradual voltage increase can be caused by a gradual increase in moisture between index finger  1304  and middle finger  1316 . In other examples, this gradual voltage increase can be caused by a gradual increase in resistance or impedance between index finger  1304  and middle finger  1316 . At time t 4 , after a temporary downward voltage spike at  1342 , the amplitude of sense output signal  1344  returns to v 1  because grounding path  1340  is no longer present. 
     In some examples, circuitry within device  1302  (e.g., an ADC or other circuitry) can be used to capture voltage levels and determine when the sense output is above, below or within various voltage thresholds, such as above voltage threshold vth 1  or below voltage threshold vth 2 . However, because voltage levels by themselves may not be sufficient to unambiguously identify a signature and determine that a particular gesture has occurred, in some examples time durations can also be monitored. Time durations can be determined and monitored using timing circuits and/or algorithms within device  1302  to evaluate signal transition times, shapes, durations, etc. 
     In the example of  FIG.  13 C , when sense output signal  1344  is determined to be above vth 1  at time t 1 , a timer can be started (e.g., clock cycles can be counted, a capacitance can be charged, etc.) to confirm that the sense output signal remains above vth 1  for a first time period (e.g., until time t 2 ), which can indicate a steady state “break” condition where index finger  1304  is not touching any other finger or thumb. At time t 2 , when sense output signal  1344  drops from v 1  to v 2 , it can be determined whether the sense output signal has fallen with a requisite steepness. When the voltage level is confirmed to have dropped below vth 2  with a requisite steepness, it can then be determined how long the sense output signal stays below voltage threshold vth 2 . In one example, when the sense output falls below voltage threshold vth 2  with a requisite steepness, but only for a second time period less than the time from t 2  to t 3 , it can be determined that index finger  1304  and middle finger  1316  contact has occurred. When sense output signal  1344  returns to a voltage level above voltage threshold vth 1  at time t 4  with a requisite steepness and stays at that level for a third time period, it can be determined that index finger  1304  and middle finger  1316  have separated and returned to the steady state condition. 
       FIG.  14 A  illustrates hand  1400  with index finger  1404  supporting wearable device (e.g., ring)  1402  and in contact with middle finger  1416  according to examples of the disclosure. Device  1402  can include ground electrode  1408 , drive electrode  1410 , differential sense electrodes  1412  and  1 , and other electronics not shown in  FIG.  14 A . Grounding path  1440  can be generated between sense electrode  1414  and ground electrode  1408  through middle finger  1416 . The order of ground electrode  1408 , drive electrode  1410 , differential sense electrodes  1412  and  1414  need not be as shown in the example of  FIG.  14 A , and in other examples the order of electrodes can be rearranged. In addition, in other examples a single-ended sense electrode can be utilized instead of differential sense electrodes  1412  and  1414 . 
       FIG.  14 B  illustrates the hand of  FIG.  14 A , except that thumb  1406  is now making contact with already touching index finger  1404  and middle finger  1416  according to examples of the disclosure. Grounding path  1448  can be formed between sense electrode  1414  and ground electrode  1408  through thumb  1406 . 
       FIG.  14 C  illustrates sense output signal  1446  detected at device  1402  when thumb  1406  makes and breaks contact with already touching index finger  1404  and middle finger  1416  according to examples of the disclosure. In the example of  FIG.  14 C , sense output signal  1446  can be derived from an output of an instrumentation amplifier or other circuitry in device  1402 . For example, raw differential sense signals can be received at sense electrodes  1412  and  1414 , and sense output signal  1446  can be a selected peak of an FFT of the raw differential sense signals over time. Alternatively, filtering, rectification and envelope detection as described above can also be used to generate sense output signal  1446 . Sense output signal  1446  can represent a “signature” of thumb  1406  coming into contact with already touching index finger  1404  and middle finger  1416 , and therefore detection of this signature can enable device  1402  to determine that an input gesture comprised of a thumb coming into contact with already touching index and middle fingers has been received. 
     At time t 1 , index finger  1404  and middle finger  1416  are not touching (as shown in  FIG.  13 A ), and a stimulation signal generated at drive electrode  1410  can propagate through index finger  1404  to differential sense electrodes  1412  and  1414 , producing voltage v 1  on sense output signal  1446 . At time t 2 , index finger  1404  and middle finger  1416  contact each other (as shown in  FIG.  14 A ), which can provide grounding path  1440  between sense electrode  1414  and ground electrode  1408  through the middle finger. Grounding path  1440  (hidden in  FIG.  14 B ) can result in a greater voltage difference between differential sense electrodes  1412  and  1414 , which can cause a resultant drop in the amplitude of sense output signal  1446  to v 2 . After time t 2 , sense output signal  1446  can increase over time in what can appear to be a roughly logarithmic curve until time t 4 , when thumb  1406  comes into contact with touching index finger  1404  and middle finger  1416 . 
     At time t 4 , with thumb  1406  now in contact with touching index finger  1404  and middle finger  1416 , an abrupt rise in the amplitude of sense output signal  1446  to v 3  (above vth 3 ) can occur, where v 3  can be greater than v 1 . At time t 5 , thumb  1406  can separate from touching index finger  1404  and middle finger  1416 , resulting in sense output signal  1446  returning to a voltage level between vth 1  and vth 2 . 
     In some examples, circuitry within device  1402  (e.g., ADC or other circuitry) can be used to capture voltage levels and determine when the sense output is above, below or within various voltage thresholds vth 1 , vth 2  or vth 3 . However, because voltage levels by themselves may not be sufficient to unambiguously identify a signature and determine that a particular gesture has occurred, in some examples time durations can also be monitored. Time durations can be determined and monitored using timing circuits and/or algorithms within device  1402  to evaluate signal transition times, shapes, durations, etc. 
     In the example of  FIG.  14 C , when sense output signal  1446  is determined to be above vth 1  at time t 1 , a timer can be started (e.g., clock cycles can be counted, a capacitance can be charged, etc.) to confirm that the sense output signal remains above vth 1  for a first time period (e.g., until time t 2 ), which can indicate a steady state “break” condition where index finger  1404  is not touching any other finger or thumb. At time t 2 , when sense output signal  1446  drops from v 1  to v 2 , it can be determined whether the sense output signal has fallen with a requisite steepness. When the voltage level is confirmed to have fallen below voltage threshold vth 2  with a requisite steepness, it can then be determined how long the sense output signal stays below voltage threshold vth 2 . In one example, when the amplitude of sense output signal  1446  falls below voltage threshold vth 2  with a requisite steepness, but only for a second timer period less than the time from t 2  to t 3 , it can be determined that index finger  1404  and middle finger  1416  contact has occurred. While sense output signal  1446  is between vth 1  and vth 2  (indicative of touching index finger  1404  and middle finger  1416 ), if the amplitude of sense output signal  1446  then rises at time t 4  with a requisite steepness to a voltage v 3  such that it exceeds voltage threshold vth 3 , it can further be determined that thumb  1406  has been added to the touching index and middle fingers. If sense output signal  1446  then drops back down at time t 5  to between vth 1  and vth 2  with a requisite steepness, it can further be determined that thumb  1406  has broken contact with touching index finger  1404  and middle finger  1416 . 
       FIG.  15 A  illustrates hand  1500  with index finger  1504  supporting wearable device (e.g., ring)  1502  and making contact with thumb  1506  according to examples of the disclosure. Device  1502  can include ground electrode  1508 , drive electrode  1510 , differential sense electrodes  1512  and  1514 , and other electronics not shown in  FIG.  15 A . The order of ground electrode  1508 , drive electrode  1510 , differential sense electrodes  1512  and  1514  need not be as shown in the example of  FIG.  15 A , and in other examples the order of electrodes can be rearranged. In addition, in other examples a single-ended sense electrode can be utilized instead of differential sense electrodes  1512  and  1514 . 
       FIG.  15 B  illustrates the hand of  FIG.  15 A , except that middle finger  1516  is now making contact with already touching index finger  1504  and thumb  1506  according to examples of the disclosure. 
       FIG.  15 C  illustrates sense output signal  1550  detected at device  1502  when middle finger  1516  makes and breaks contact with already touching index finger  1504  and thumb  1506  according to examples of the disclosure. In the example of  FIG.  15 C , sense output signal  1550  can be derived from an output of an instrumentation amplifier or other circuitry in device  1502 . For example, raw differential sense signals can be received at sense electrodes  1512  and  1514 , and sense output signal  1550  can be a selected peak of an FFT of the raw differential sense signals over time. Alternatively, filtering, rectification and envelope detection as described above can also be used to generate sense output signal  1550 . Sense output signal  1550  can represent a “signature” of middle finger  1516  coming into contact with already touching index finger  1504  and thumb  1506 , and therefore detection of this signature can enable device  1502  to determine that an input gesture comprised of a middle finger coming into contact with already touching index finger and thumb has been received. 
     At time t 1 , index finger  1504  and thumb  1506  are not touching, and a stimulation signal generated at drive electrode  1510  can propagate through index finger  1504  to differential sense electrodes  1512  and  1514 , producing voltage v 1  on sense output signal  1550  at the output of the sense circuitry in device  1502 . At time t 2 , index finger  1504  and thumb  1506  contact each other (as shown in  FIG.  15 A ), which can provide a grounding path between sense electrode  1514  and ground electrode  1508  through the thumb. The grounding path can result in a greater voltage difference between differential sense electrodes  1512  and  1514 , which can cause a resultant drop in the amplitude of sense output signal  1550  to v 2 . At time t 3 , middle finger  1516  can come into contact with touching index finger  1504  and thumb  1506 , and an abrupt rise in the amplitude of sense output signal  1550  to v 3  can occur. At time t 4 , middle finger  1516  can separate from touching index finger  1504  and thumb  1506 , resulting in the amplitude of sense output signal  1550  returning to a voltage level less than vth 2 . 
     In some examples, circuitry within device  1502  (e.g., ADC or other circuitry) can be used to capture voltage levels and determine when the sense output is above, below or between any of voltage thresholds vth 1 , vth 2  or vth 3 . However, because voltage levels by themselves may not be sufficient to unambiguously identify a signature and determine that a particular gesture has occurred, in some examples time durations can also be monitored. 
     In the example of  FIG.  15 C , when sense output signal  1550  is determined to be above vth 1  and time t 1 , a timer can be started (e.g., clock cycles can be counted, a capacitance can be charged, etc.) to confirm that the sense output signal remains above vth 1  for a first time period (e.g., until time t 2 ), which can indicate a steady state “break” condition where index finger  1504  is not touching any other finger or thumb. At time t 2 , when sense output signal  1550  drops from v 1  to v 2 , it can be determined whether the sense output signal has fallen with a requisite steepness. When the voltage level is confirmed to have dropped below voltage threshold vth 2  with a requisite steepness, it can then be determined how long the sense output stays below voltage threshold vth 2 . In one example, when the sense output signal falls below voltage threshold vth 2  with a certain steepness and stays below voltage threshold vth 2  for a second time period until at least time t 3 , it can be determined that an index finger  1504  and thumb  1506  contact (e.g., an index finger-thumb pinch) has occurred. At time t 4 , middle finger  1516  can come into contact with touching index finger  1504  and thumb  1506 , and an abrupt rise in sense output signal  1550  to v 3  (greater than v 1 ) can occur. At time t 5 , middle finger  1516  can separate from touching index finger  1504  and thumb  1506 , resulting in the amplitude of sense output signal  1550  returning to a voltage level less than vth 2 . 
       FIG.  16 A  illustrates left hand  1600  with index finger  1604  supporting wearable device (e.g., ring)  1602  and making contact with opposite, right hand  1652  according to examples of the disclosure. Although the example of  FIG.  16 A  shows device  1602  over index finger  1604 , it should be understood that in other examples device  1602  can be worn over other fingers such as middle finger  1616 . Device  1602  can include ground electrode  1608 , drive electrode  1610 , differential sense electrodes  1612  and  1614 , and other electronics not shown in  FIG.  16 A . The order of ground electrode  1608 , drive electrode  1610 , differential sense electrodes  1612  and  1614  need not be as shown in the example of  FIG.  16 A , and in other examples the order of electrodes can be rearranged. In addition, in other examples a single-ended sense electrode can be utilized instead of differential sense electrodes  1612  and  1614 . 
     Although index finger  1604  in the example of  FIG.  16 A  is not touching thumb  1606  (as in  FIG.  12 B ), nevertheless the sense output signal “signature” can be similar to that shown in  FIG.  12 C , because a similar grounding path  1654  (similar to grounding path  1238  in  FIG.  12 B ) can be present between sense electrode  1614  and ground electrode  1608  via the user&#39;s body. Accordingly, in some examples a separate camera can be employed to distinguish between the gesture of  FIG.  12 B  and the gesture of  FIG.  16 A . 
       FIG.  16 B  illustrates left hand  1600  with index finger supporting wearable device (e.g., ring)  1602 A and also right hand  1652  with index finger  1656  supporting wearable device (e.g., ring)  1602 B according to examples of the disclosure. Although the example of  FIG.  16 B  shows device  1602 A over index finger  1604  of left hand  1600 , and device  1602 B over index finger  1656  of right hand  1652 , it should be understood that in other examples the devices can be worn over other fingers on the left and right hands. Having devices  1602 A and  1602 B on both hands can enable a user to provide the gesture inputs described above with either hand, either separately or simultaneously. 
     In addition, in some examples, the stimulation frequency applied to the drive electrode of device  1602 A can be different from the stimulation frequency applied to the drive electrode of device  1602 B. By providing different stimulation frequencies on devices  1602 A and  1602 B, the ambiguity presented by receiving a similar output waveform “signature” from the index finger-thumb gesture of  FIG.  12 B  and also the index finger-opposite hand gesture of  FIG.  16 A  can be resolved without requiring a camera. For example, if device  1602 A generates a 5 MHz stimulation signal and device  1602 B generates an 8 MHz stimulation signal, then an index finger-thumb input gesture generated by device  1602 A on left hand  1600  can produce the sense output signature of  FIG.  12 C  at 5 MHz at device  1602 A. However, if index finger  1604  of left hand  1600  touches right hand  1652 , the 8 MHz stimulation signal generated by device  1602 B of the right hand can couple onto device  1602 A of the left hand, and the sense output signal at device  1602 A can be a composite signal having both 5 MHz and 8 MHz components. These frequency components can be separately detected to unambiguously determine that index finger  1604  of left hand  1600  is touching right hand  1652  (rather than left thumb  1606 ). 
       FIG.  16 C  illustrates left hand  1600  with index finger  1604  supporting wearable device (e.g., ring)  1602 A and middle finger  1616  supporting wearable device (e.g., ring)  1602 B according to examples of the disclosure. Wearing devices on two fingers of the same hand can allow a user to perform additional input gestures using a single hand, such as a middle finger-thumb pinch gesture similar to the index finger-thumb pinch gesture of  FIGS.  12 A- 12 C . Although  FIG.  16 C  shows devices on index finger  1604  and middle finger  1616 , in other examples devices can be worn on any combination of index, middle, ring, and pinky fingers to provide additional input gesture possibilities. 
       FIG.  17    illustrates a flowchart for detecting input gestures using one or more devices according to examples of the disclosure. In the example of  FIG.  17   , at block  1758  one or more devices can be worn on one or more fingers of one or both hands. At block  1760 , each device can generate a stimulation signal at a different frequency. At block  1762 , sense output signal amplitudes can be captured at each device over time. At block  1764 , the amplitudes of sense output signals can be compared to various voltage and time thresholds/windows to identify an input gesture signature and the gesture being performed. At block  1766 , different operations can be initiated, controlled or performed based on the identified gesture. 
     Therefore, according to the above, some examples of the disclosure are directed to a system. The system can comprise sense circuitry and processing circuitry. The sense circuitry can be coupled to a sense electrode, the sense circuitry configured to sense a signal at the sense electrode in response to a drive signal applied to a first body part. The sense electrode can be configured to contact a second body part, different from the first body part. The processing circuitry can be configured to: in accordance with a determination that one or more criteria are met, detect contact between the first body part and the second body part; and in accordance with a determination that the one or more criteria are not met, detect no contact between the first body part and the second body part. The one or more criteria can include a first criterion that is met when an amplitude of the sensed signal exceeds an amplitude threshold and a second criterion that is met when the sensed signal has a non-distorted waveform. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the processing circuitry can be further configured to: in accordance with a determination that the first criteria is met and that the second criterion is not met, detecting proximity of the first body part to the second body part without contact between the first body part and the second body part. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the system can further comprise: drive circuitry coupled to a drive electrode. The drive circuitry can be configured to apply the drive signal to the drive electrode, and the drive electrode can be configured to contact the first body part. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining whether the amplitude of the sensed signal exceeds the amplitude threshold can comprise identifying a peak in a frequency domain representation of the sensed signal and comparing the peak identified in the frequency domain with the amplitude threshold in the frequency domain. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining whether the sensed signal has a non-distorted waveform can comprise comparing a width of the peak identified in the frequency domain with a width threshold. In accordance with a determination that the width is below the width threshold, determining that the sensed signal has the non-distorted waveform; and in accordance with a determination that the width is above the width threshold, determining that the sensed signal has a distorted waveform. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining whether the sensed signal has a non-distorted waveform can comprise comparing an amplitude-normalized width of the peak identified in the frequency domain with a width threshold. In accordance with a determination that the amplitude-normalized width is below the width threshold, determining that the sensed signal has the non-distorted waveform; and in accordance with a determination that the amplitude-normalized width is above the width threshold, determining that the sensed signal has a distorted waveform. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining whether the received sensed has a non-distorted waveform can comprise identifying a second peak in the frequency domain representation of the sensed signal, the second peak at a lower frequency than the first peak, and comparing the second peak identified in the frequency domain with a second amplitude threshold in the frequency domain. In accordance with a determination that an amplitude of the second peak is below the second amplitude threshold, determining that the sensed signal has the non-distorted waveform; and in accordance with a determination that the amplitude of the second peak is above the second amplitude threshold, determining that the sensed signal has a distorted waveform. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining whether the sensed signal has a non-distorted waveform can comprise correlating the sensed signal with a reference signal. In accordance with a determination that the correlation is above a correlation threshold, determining that the sensed signal has the non-distorted waveform; and in accordance with a determination that the correlation is below the correlation threshold, determining that the sensed signal has a distorted waveform. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the drive signal can have a frequency greater than 500 kHz or between 1-10 MHz. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the drive signal can be a square wave. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first body part can comprise a first wrist and hand and the second body part can comprise a second wrist and hand. Additionally or alternatively to one or more of the examples disclosed above, in some examples, detecting contact between the first body part and the second body part can comprise detecting contact between a finger of a first hand and a palm or a finger of a second hand. 
     Some examples of the disclosure are directed to a method. The method can comprise: at a device comprising sense circuitry and processing circuitry: sensing, via sense circuitry, a signal at a sense electrode configured to contact a first body part, in response to a drive signal applied by a drive electrode configured to contact a second body part, different from the first body part; and in accordance with a determination that one or more criteria are met, detecting contact between the first body part and the second body part; and in accordance with a determination that the one or more criteria are not met, detecting no contact between the first body part and the second body part. The one or more criteria can include a first criterion that is met when an amplitude of the sensed signal exceeds an amplitude threshold and a second criterion that is met when the sensed signal has a non-distorted waveform. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method can further comprise: in accordance with a determination that the first criteria is met and that the second criterion is not met, detecting proximity of the first body part to the second body part without contact between the first body part and the second body part. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining whether the amplitude of the sensed signal exceeds the amplitude threshold can comprise identifying a peak in a frequency domain representation of the sensed signal and comparing the peak identified in the frequency domain with the amplitude threshold in the frequency domain. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining whether the sensed signal has a non-distorted waveform can comprise comparing a width of the peak identified in the frequency domain with a width threshold. In accordance with a determination that the width is below the width threshold, determining that the sensed signal has the non-distorted waveform; and in accordance with a determination that the width is above the width threshold, determining that the sensed signal has a distorted waveform. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining whether the sensed signal has a non-distorted waveform can comprise comparing an amplitude-normalized width of the peak identified in the frequency domain with a width threshold. In accordance with a determination that the amplitude-normalized width is below the width threshold, determining that the sensed signal has the non-distorted waveform; and in accordance with a determination that the amplitude-normalized width is above the width threshold, determining that the sensed signal has a distorted waveform. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining whether the received sensed has a non-distorted waveform can comprise identifying a second peak in the frequency domain representation of the sensed signal, the second peak at a lower frequency than the first peak, and comparing the second peak identified in the frequency domain with a second amplitude threshold in the frequency domain. In accordance with a determination that an amplitude of the second peak is below the second amplitude threshold, determining that the sensed signal has the non-distorted waveform; and in accordance with a determination that the amplitude of the second peak is above the second amplitude threshold, determining that the sensed signal has a distorted waveform. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining whether the sensed signal has a non-distorted waveform can comprise correlating the sensed signal with a reference signal. In accordance with a determination that the correlation is above a correlation threshold, determining that the sensed signal has the non-distorted waveform; and in accordance with a determination that the correlation is below the correlation threshold, determining that the sensed signal has a distorted waveform. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the drive signal can have a frequency greater than 500 kHz or between 1-10 MHz. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the drive signal can be a square wave. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first body part can comprise a first wrist and hand and the second body part can comprise a second wrist and hand. Additionally or alternatively to one or more of the examples disclosed above, in some examples, detecting contact between the first body part and the second body part can comprise detecting contact between a finger of a first hand and a palm or a finger of a second hand. Some examples of the disclosure are directed to a non-transitory computer readable storage medium. The non-transitory computer readable storage medium can store instructions (e.g., one or more programs), which when executed by one or more processors of an electronic device, can cause the electronic device to perform any of the above methods. 
     Some examples of the disclosure are directed to a system. The system can comprise sense circuitry and processing circuitry. The sense circuitry can be coupled to a sense electrode, the sense circuitry configured to sense a signal at the sense electrode in response to a drive signal applied to a first finger of a hand, and the sense electrode configured to contact a second finger of the hand, different from the first finger. The processing circuitry can be configured to: in accordance with a determination that one or more criteria are met, detect a movement gesture; and in accordance with a determination that the one or more criteria are not met, forgo detecting the movement gesture. The one or more criteria can include a first criterion indicative of contact between the first finger and the second finger and a second criterion indicative of movement of the first finger along the second finger. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first criterion can be met when an amplitude of the sensed signal exceeds an amplitude threshold. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first criterion can be met when an amplitude of the sensed signal exceeds an amplitude threshold and when the sensed signal has a non-distorted waveform. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the second criterion can be met when an amplitude of the sensed signal increases or decreases by a threshold amount subsequent to and while the first criterion is met. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the movement gesture can be a slide gesture. Additionally or alternatively to one or more of the examples disclosed above, in some examples, in accordance with a determination that an amplitude of the sensed signal increases from an initial value (by a threshold amount), the detected movement gesture can be a slide-toward gesture. Additionally or alternatively to one or more of the examples disclosed above, in some examples, in accordance with a determination that an amplitude of the sensed signal decreases from an initial value (by a threshold amount), the detected movement gesture can be a slide-away gesture. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first electrode can be configured to contact the first finger at or near the base of the first finger and the second electrode can be configured to contact the second finger at or near the base of the second finger. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first finger can be a thumb and the second finger can be an index finger. The first electrode can be configured to contact the first finger at or near the middle of the thumb, and the second electrode can be configured to contact the index finger at or near the base of the index finger. 
     Some examples of the disclosure are directed to a method. The method can comprise: at a device comprising sense circuitry and processing circuitry: sensing, via sense circuitry, a signal at a sense electrode in response to a drive signal applied by a drive electrode configured to contact a first finger of a hand, the sense electrode configured to contract a second finger of the hand, different from the first finger; and in accordance with a determination that one or more criteria are met, detect a movement gesture; and in accordance with a determination that the one or more criteria are not met, forgo detecting the movement gesture. The one or more criteria can include a first criterion indicative of contact between the first finger and the second finger and a second criterion indicative of movement of the first finger along the second finger. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first criterion can be met when an amplitude of the sensed signal exceeds an amplitude threshold. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first criterion can be met when an amplitude of the sensed signal exceeds an amplitude threshold and when the sensed signal has a non-distorted waveform. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the second criterion can be met when an amplitude of the sensed signal increases or decreases by a threshold amount subsequent to and while the first criterion is met. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the movement gesture can be a slide gesture. Additionally or alternatively to one or more of the examples disclosed above, in some examples, in accordance with a determination that an amplitude of the sensed signal increases from an initial value (by a threshold amount), the detected movement gesture can be a slide-toward gesture. Additionally or alternatively to one or more of the examples disclosed above, in some examples, in accordance with a determination that an amplitude of the sensed signal decreases from an initial value (by a threshold amount), the detected movement gesture can be a slide-away gesture. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first electrode can be configured to contact the first finger at or near the base of the first finger and the second electrode can be configured to contact the second finger at or near the base of the second finger. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first finger can be a thumb and the second finger can be an index finger. The first electrode can be configured to contact the first finger at or near the middle of the thumb, and the second electrode can be configured to contact the index finger at or near the base of the index finger. Some examples of the disclosure are directed to a non-transitory computer readable storage medium. The non-transitory computer readable storage medium can store instructions (e.g., one or more programs), which when executed by one or more processors of an electronic device, can cause the electronic device to perform any of the above methods. 
     Some examples of the disclosure are directed to a wearable device for detecting gestures, comprising drive circuitry coupled to a drive electrode and configured to generate a stimulation signal, the drive electrode positioned at a first location in the device for contacting a first finger of a first hand, sense circuitry coupled to at least one sense electrode and configured to generate a sense output signal based on one or more sense signals received at the at least one sense electrode in response to the stimulation signal, the at least one sense electrode positioned at a second location in the device for contacting the first finger of the first hand, and a processor communicatively coupled to the drive and sense circuitry and configured for capturing an amplitude of the sense output signal over time, and in accordance with a determination that a first set of amplitude and time criteria are met, detecting a making of contact of the first finger with an adjacent second finger of the first hand. Additionally or alternatively to one or more of the examples disclosed above, in some examples the processor is further configured for, in accordance with a determination that a second set of amplitude and time criteria are met following the determination that the first set of amplitude and time criteria are met, detecting a breaking of contact of the first finger and the adjacent second finger. Additionally or alternatively to one or more of the examples disclosed above, in some examples the processor is further configured for, in accordance with a determination that a second set of amplitude and time criteria are met following the determination that the first set of amplitude and time criteria are met, detecting a making of contact of a thumb of the first hand with the touching first and second fingers. Additionally or alternatively to one or more of the examples disclosed above, in some examples the processor is further configured for, in accordance with a determination that a third set of amplitude and time criteria are met following the determination that the second set of amplitude and time criteria are met, detecting a breaking of contact of the thumb of the first hand with the touching first finger and second fingers. Additionally or alternatively to one or more of the examples disclosed above, in some examples the determination that the first set of amplitude and time criteria are met comprises determining that the sense output signal satisfies a first voltage threshold during a first time period between a first time and a second time, determining that the sense output signal changes to satisfy a second voltage threshold at the second time, determining that the sense output signal changes and approaches the second voltage threshold while continuing to satisfy the second voltage threshold during a portion of a second time period between the second time and a third time, and determining that the sense output signal no longer satisfies the second voltage threshold at the third time. Additionally or alternatively to one or more of the examples disclosed above, in some examples the processor is further configured for, in accordance with a determination that a second set of amplitude and time criteria are met following the determination that the first set of amplitude and time criteria are met, detecting a breaking of contact of the first finger and the adjacent second finger, wherein the determination that the second set of amplitude and time criteria are met comprises determining that the sense output signal changes to satisfy the first voltage threshold at a fourth time. Additionally or alternatively to one or more of the examples disclosed above, in some examples the processor is further configured for, in accordance with a determination that a second set of amplitude and time criteria are met following the determination that the first set of amplitude and time criteria are met, detecting a making of contact of a thumb of the first hand with the touching first and second fingers, wherein the determination that the second set of amplitude and time criteria are met comprises determining that the sense output signal changes to satisfy a third voltage threshold at a fourth time. Additionally or alternatively to one or more of the examples disclosed above, in some examples the processor is further configured for, in accordance with a determination that a third set of amplitude and time criteria are met following the determination that the second set of amplitude and time criteria are met, detecting a breaking of contact of the thumb and the touching first finger and second fingers, wherein the determination that the third set of amplitude and time criteria are met comprises determining that the sense output signal changes to a voltage between the first voltage threshold and the second voltage threshold at a fifth time. Additionally or alternatively to one or more of the examples disclosed above, in some examples the at least one sense electrode comprises two differential sense electrodes, and the device further comprises a ground electrode positioned at a third location in the device for contacting the first finger of the first hand, wherein the ground electrode, the drive electrode, and the two differential sense electrodes are arranged in order in the device. 
     Some examples of the disclosure are directed to a method for detecting gestures, the method performed at a wearable device including drive circuitry, sense circuitry, and processing circuitry, the method comprising generating a stimulation signal for propagating through a first finger of a first hand, generating a sense output signal based on one or more sense signals received from the first finger of the first hand in response to the stimulation signal, capturing an amplitude of the sense output signal over time, and in accordance with a determination that a first set of amplitude and time criteria are met, detecting a making of contact of the first finger with an adjacent second finger of the first hand. Additionally or alternatively to one or more of the examples disclosed above, in some examples the method further comprises, in accordance with a determination that a second set of amplitude and time criteria are met following the determination that the first set of amplitude and time criteria are met, detecting a breaking of contact of the first finger and the adjacent second finger. Additionally or alternatively to one or more of the examples disclosed above, in some examples the method further comprises, in accordance with a determination that a second set of amplitude and time criteria are met following the determination that the first set of amplitude and time criteria are met, detecting a making of contact of a thumb of the first hand with the touching first and second fingers. Additionally or alternatively to one or more of the examples disclosed above, in some examples the method further comprises, in accordance with a determination that a third set of amplitude and time criteria are met following the determination that the second set of amplitude and time criteria are met, detecting a breaking of contact of the thumb of the first hand and the touching first finger and second fingers. Additionally or alternatively to one or more of the examples disclosed above, in some examples the determination that the first set of amplitude and time criteria are met comprises determining that the sense output signal satisfies a first voltage threshold during a first time period between a first time and a second time, determining that the sense output signal changes to satisfy a second voltage threshold at the second time, determining that the sense output signal changes and approaches the second voltage threshold while continuing to satisfy the second voltage threshold during a portion of a second time period between the second time and a third time, and determining that the sense output signal no longer satisfies the second voltage threshold at the third time. Additionally or alternatively to one or more of the examples disclosed above, in some examples the method further comprises, in accordance with a determination that a second set of amplitude and time criteria are met following the determination that the first set of amplitude and time criteria are met, detecting a breaking of contact of the first finger and the adjacent second finger, wherein the determination that the second set of amplitude and time criteria are met comprises determining that the sense output signal changes to satisfy the first voltage threshold at a fourth time. Additionally or alternatively to one or more of the examples disclosed above, in some examples the method further comprises, in accordance with a determination that a second set of amplitude and time criteria are met following the determination that the first set of amplitude and time criteria are met, detecting a making of contact of a thumb of the first hand with the touching first and second fingers, wherein the determination that the second set of amplitude and time criteria are met comprises determining that the sense output signal changes to satisfy a third voltage threshold at a fourth time. Additionally or alternatively to one or more of the examples disclosed above, in some examples the method further comprises, in accordance with a determination that a third set of amplitude and time criteria are met following the determination that the second set of amplitude and time criteria are met, detecting a breaking of contact of the thumb and the touching first finger and second fingers, wherein the determination that the third set of amplitude and time criteria are met comprises determining that the sense output signal changes to a voltage between the first voltage threshold and the second voltage threshold at a fifth time. 
     Some examples of the disclosure are directed to a wearable device for detecting gestures, comprising drive circuitry coupled to a drive electrode and configured to generate a stimulation signal, the drive electrode positioned at a first location in the device for contacting a first finger of a first hand, sense circuitry coupled to at least one sense electrode and configured to generate a sense output signal based on one or more sense signals received at the at least one sense electrode in response to the stimulation signal, the at least one sense electrode positioned at a second location in the device for contacting the first finger of the first hand, and a processor communicatively coupled to the drive and sense circuitry and configured for capturing an amplitude of the sense output signal over time, in accordance with a determination that a first set of amplitude and time criteria are met, detecting a making of contact of the first finger with a thumb of the first hand, and in accordance with a determination that a second set of amplitude and time criteria are met following the determination that the first set of amplitude and time criteria are met, detecting a making of contact of a second finger adjacent to the first finger of the first hand with the touching first finger and thumb. Additionally or alternatively to one or more of the examples disclosed above, in some examples the processor is further configured for, in accordance with a determination that a third set of amplitude and time criteria are met following the determination that the second set of amplitude and time criteria are met, detecting a breaking of contact of the second finger with the touching first finger and thumb. 
     Some examples of the disclosure are directed to a method for detecting gestures, the method performed at a wearable device including drive circuitry, sense circuitry, and processing circuitry, the method comprising generating a stimulation signal for propagating through a first finger of a first hand, generating a sense output signal based on one or more sense signals received from the first finger of the first hand in response to the stimulation signal, capturing an amplitude of the sense output signal over time, in accordance with a determination that a first set of amplitude and time criteria are met, detecting a making of contact of the first finger with a thumb of the first hand, and in accordance with a determination that a second set of amplitude and time criteria are met following the determination that the first set of amplitude and time criteria are met, detecting a making of contact of a second finger adjacent to the first finger of the first hand with the touching first finger and thumb. 
     Although examples of this disclosure have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of examples of this disclosure as defined by the appended claims.

Metadata:
Filing Date: 20230331
Publication Date: 20240326
Grant Date: 20240326
Priority Date: 20200331
Inventors: BEYHS, MICHAEL J.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/014", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/017", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/014", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/014", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/017", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/163", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/017", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 77854515