Abstract:
In one aspect of the teachings herein, a physical activity tracking system includes a wearable electronic device that uses dual touch points for detecting control inputs by a user. Processing within the device complements the dual touch point interface by requiring simultaneous touch detections to register user inputs to the device, and by mapping dual-touch detections of different duration to different control actions. Use of the dual-touch arrangement and the associated processing provides a number of advantages, including intuitive operation and minimization of accidental activations by the user. Other advantages of the touch interface include the ability to seat or mount the device in a variety of carriers, such as bracelets, etc., that complement wearability of the device, while still allowing for convenient charging.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119(e) from the provisional U.S. application filed on 18 Sep. 2014 and identified by App. No. 62/052,198. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to tracking physical activity and particularly relates to a tracking device, associated communication devices, and an online server that cooperatively provide a system for tracking physical activity. 
       BACKGROUND 
       [0003]    A growing interest in adopting and maintaining healthy lifestyles corresponds to the growing “wearables” market and the device and information ecosystems supporting them. “Wearables” here means electronic devices that are designed to be worn, carried or affixed to their users. Some wearables are information-centric, such as seen in the various smart-watch solutions available in the consumer market. Many wearables, however, focus on user fitness and provide a range of fitness-related tracking functions. 
         [0004]    Well-known functions include step counting and caloric consumption. As sensor technologies improve, along with improvements in battery technology and low-power circuitry, additional functions are becoming more common. Examples include continuous heart-rate monitoring, GPS tracking, and the like. 
         [0005]    However, designing a wearable fitness tracker and developing a corresponding overall physical activity tracking system poses many challenges. Users expect convenience but the concept of convenience becomes complex in the wearables category. Wearables must be small enough to be unobtrusive, but users more broadly seek a satisfying “user experience.” 
         [0006]    Providing such experiences requires system designers and manufacturers to balance aesthetics against practicality and durability, all while minding cost limits and underlying performance requirements. It is recognized herein that the form factor of a wearable device must provide intuitive, hassle-free operation for the active user, while simultaneously harmonizing aesthetics, form factor considerations, and the ability to seamlessly integrate the device into an overall physical activity tracking system. 
       SUMMARY 
       [0007]    In one aspect of the teachings herein, a physical activity tracking system includes a wearable electronic device that uses dual touch points for detecting control inputs by a user. Processing within the device complements the dual touch point interface by requiring simultaneous touch detections to register user inputs to the device, and by mapping dual-touch detections of different duration to different control actions. Use of the dual-touch arrangement and the associated processing provides a number of advantages, including intuitive operation and minimization of accidental activations by the user. Other advantages of the touch interface include the ability to seat or mount the device in a variety of carriers, such as bracelets, etc. Mounting flexibility complements the wearability and usability of the device, while still allowing for convenient charging. 
         [0008]    In an example embodiment, a wearable electronic device includes a housing having an exterior surface and electronic circuitry mounted within the housing. The electronic circuitry includes a touch-sensing circuit configured to provide two touch points on the exterior surface of the housing, where the two touch points are physically separated on the exterior surface so as to prevent accidental touch activation of the wearable electronic device by a user. The electronic circuitry further includes a processing circuit operatively associated with the touch-sensing circuit and configured to control one or more functions of the wearable electronic device, responsive to detecting dual-touch events in which the user simultaneously touches both touch points. 
         [0009]    In another embodiment, a physical activity tracking system includes a wearable electronic device configured for tracking the physical activity of a user. The wearable electronic device includes a housing having an exterior surface and electronic circuitry mounted within the housing. The electronic circuitry includes a touch-sensing circuit configured to provide two touch points on the exterior surface of the housing, where the two touch points are physically separated on the exterior surface so as to prevent accidental touch activation of the wearable electronic device by the user. Further included are a display positioned beneath a transparent region of the exterior top surface of the housing and configured to display one or more items of information to the user, at least one sensor for sensing physical activity of the user, including at least one of a motion sensor and a barometric pressure sensor, and a processing circuit operatively associated with the touch-sensing circuit, the display and the at least one sensor. 
         [0010]    The processing circuit is configured to track the physical activity of the user based on processing sensor output from the at least one sensor. Further, the processing circuit is configured to control operation of the wearable electronic device, including operation of the display, responsive to detecting dual-touch events in which the user simultaneously touches both touch points. 
         [0011]    In yet another embodiment, a physical activity tracking system includes a wearable electronic device configured for tracking the physical activity of a user. The wearable electronic device includes a housing having an exterior surface defining an interior space, and a clip assembly that includes an external clip comprising an elongate member extending along an exterior bottom surface of the housing and having first and second ends, an internal spring comprising an elongate member having first and second ends extending within the interior space of the housing roughly parallel to the external clip when the external clip is in its normally closed positioned. The clip assembly further includes a stem assembly rigidly coupling the first end of the external clip to the corresponding first end of the internal spring, and having a defined stem length that maintains the first ends of the external clip and internal spring in a spaced apart relationships. Still further, the clip assembly includes an interior retaining feature within the housing configured to prevent the second end of the interior spring from moving towards the external clip when the second end of the external clip is deflected away from the exterior bottom surface of the housing, thereby creating a spring force opposing such deflection. 
         [0012]    Of course, the present invention is not limited to the above features and advantages. Those of ordinary skill in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a block diagram of one embodiment of a system for tracking the physical activity of one or more users. 
           [0014]      FIG. 2  is a perspective view of a wearable device for tracking the physical activity of a user, which device is referred to herein as a “tracker.” 
           [0015]      FIGS. 3 and 4  are side and bottom views, respectively, of the tracker introduced in  FIG. 2 . 
           [0016]      FIG. 5  is a perspective view of one embodiment of a charging station, having charging contacts mounted along a body section that is dimensioned so as to allow mounting of a bracelet/tracker assembly for charging. 
           [0017]      FIG. 6  is a perspective view of one embodiment of a bracelet that is specially adapted as a carrier for the tracker of  FIG. 2 , for both enhancing the wearability of the tracker and for mounting of the tracker on the charging station of  FIG. 5   
           [0018]      FIG. 7  is a plan view of the bracelet introduced in  FIG. 6 . 
           [0019]      FIG. 8  is a block diagram of example circuitry for the tracker introduced in  FIG. 1 . 
           [0020]      FIG. 9  is a logic flow diagram of one embodiment of a method of touch-based processing implemented by a tracker having a touch interface. 
           [0021]      FIG. 10  is a bottom perspective view of a tracker illustrating example details for a clip assembly that facilitates the wearability of the tracker. 
           [0022]      FIGS. 11 and 12  are cutaway side and perspective views, respectively, illustrating the clip assembly in further detail and shown in context with the tracker housing. 
           [0023]      FIG. 13  is a perspective view of the clip assembly in one embodiment. 
           [0024]      FIGS. 14A and 14B  illustrate operation of the clip assembly in one or more embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]      FIG. 1  illustrates one embodiment of an activity tracking system  8 , including a physical-activity tracking device  10 , referred to as a “tracker  10 .” The below description details a number of innovative physical and/or functional features implemented in the tracker  10 , including a “pinch” or “dual touch” feature that provides comprehensive interaction capabilities between the tracker  10  and its user, while simultaneously providing robust rejection of “false” inputs. The tracker  10  further provides an advantageous clipping mechanism—not shown in FIG.  1 —that provides a secure yet easily manipulated engagement mechanism for coupling to a body-worn carrier. Of course, these advantages are non-limiting examples of the numerous advantages provided by the tracker  10  and overall system  8 . 
         [0026]    In more detail, the tracker  10  includes a communication interface  12  and a processing circuit  14  that includes or is otherwise associated with storage  16 . In an example case, the storage  16  comprises a non-transitory computer-readable medium storing a computer program  18 , physical activity data (“PAD”)  20 , and one or more items of configuration data  22 . 
         [0027]    The tracker  10  additionally includes a display  24  configured to display various items of information, such as tracker status or operational information, mode information, battery charge information, one or more items of PAD  20  or data derived therefore, etc. Further, the tracker  10  includes a touch circuit  26  and at least two touch sensors  28 -A and  28 -B, which are used in “dual-touch” or “pinch” related processing as taught herein. Still further, the tracker  10  includes a motion sensor  30 , such as a multi-axis accelerometer, and an altimeter or barometer  32 . 
         [0028]    Here and elsewhere in this disclosure, recitation of a feature or item in the singular sense shall be understood as meaning “one or more” of such features or items unless otherwise noted. For example, the communication interface  12  may comprise one or more communication interfaces, e.g., supporting different wireless communication technologies. In another example, the processing circuit  14  comprises one or more processing circuits, such as one or more microprocessors, microcontrollers, Digital Signal Processors (DSPs), Field Programmable Gate Arrays (FPGAs), Complex Programmable Logic Devices (CPLDs), Application Specific Integrated Circuits (ASICs), or other digital processing circuitry. 
         [0029]    Similarly, the storage  16  may be wholly or partly integrated with the processing circuit  14 , or communicatively coupled thereto, and may comprise more than one storage element or device, e.g., such as two or more types of memory. Examples include SRAM configured as working memory for the processing circuit  14  and EEPROM or FLASH memory configured as non-volatile, persistent storage for the computer program  18 , the PAD  20  and any configuration data  22 . In at least one such embodiment, the processing circuit  14  is configured to carry out the processing and supporting algorithms disclosed herein, based at least in part on its execution of computer program instructions comprising the computer program  18 , which instructions may be held in working memory for execution. 
         [0030]      FIG. 1  serves as a non-limiting example implementation of the tracker  10 . Broadly, the processing circuit  14  may be implemented using fixed circuitry, programmed circuitry, or some mix thereof. 
         [0031]    Continuing with a top-level description of  FIG. 1 , one sees a communication device  40 , which may also be referred to as a “personal computing device” or PCD. In the example illustration, the communication device  40  includes a communication interface  42 , along with a processing circuit  44 . The processing circuit  44  is associated with storage  46 , which stores a computer program  48 —also referred to as an “app  48 ” or “application  48 ”—and further stores PAD  50  and, possibly, one or more items of configuration data  52 . The PAD  50  may be a full or partial copy of the PAD  20  stored in the tracker  10 , or may be a historical aggregation of PAD  20  as transferred from the tracker  10  to the communication device  40  in any number of past transfer events, or may be data derived from one or more items of PAD  20  transferred from the tracker  10 . 
         [0032]    For example, the PAD  50  may include accumulations or averages of pedometer data, as obtained from the tracker&#39;s monitoring and processing of data from the motion sensor  30 . Additionally or alternatively, the PAD  50  may include accumulations or averages of barometric or elevation change data. In a non-limiting example, the app  48  is configured to obtain and process the PAD  20  at triggered and/or scheduled times, and to accumulate or otherwise process and aggregate the PAD  20 , to form the PAD  50 . Thus, the PAD  50  may comprise various items of PAD  20  transferred in from the tracker  10  and then aggregated or otherwise processed by the app  48  in terms of discrete physical activity events—e.g., a run or a workout—or in temporal terms, such as steps taken per day, per week, etc. 
         [0033]    In at least some embodiments, the communication device  40  comprises a smartphone or an electronic tablet having both local and wide-area wireless communication capabilities. For example, the communication interface  42  includes a BLUETOOTH radio interface for communicatively coupling to the tracker  10 . Other Radio Access Technologies (RATs) may be used to couple the tracker  10  to the communication device  40 , such as Near Field Communication (NFC) links, ZIGBEE, Ultra Wideband (UWB). In other examples, inductive or optical coupling interfaces provide the local communication link between the tracker  10  and the communication device  10 . Non-limiting examples of the communication device  40  include an APPLE IPHONE or IPAD device, or a SAMSUNG GALAXY phone or tablet. 
         [0034]    In an example of wide-area connectivity, the communication device  40  includes a cellular radio modem for communications toward an access network  54 . By way of non-limiting example, the access network  54  comprises a Public Land Mobile Network (PLMN), such as a Long Term Evolution (LTE) Radio Access Network (RAN) supported by an Evolved Packet Core (EPC). In any case, the access network  54  communicatively links the communication device  40  through the Internet  56  to an online computer system  60 . More particularly, the access network  54  and Internet  56  communicatively link the app  48  to the online computer system  60 , thereby allowing the app  48  to transfer PAD  50  from the communication device  40  to the online computer system  60 , e.g., for storage in or linking to a user account corresponding to the user/owner of the communication device  40 . 
         [0035]    In this regard, it shall be understood that different trackers  10  generally are purchased and used by different users, e.g., an individual user owns and wears a given tracker  10 , to track her physical activity. Thus, while  FIG. 1  illustrates one tracker  10  and one communication device  40 , the overall system  8  may be considered as including any number of trackers  10  and associated apps  48  running in respective ones of the users&#39; corresponding communication devices  40 . 
         [0036]    Correspondingly, the online computer system  60  is configured to communicate with a potentially large plurality of communication devices  40  and/or trackers  10 . More particularly, the online computer system  60  is configured to manage account data for a potentially large number of (tracker users), including storing and processing PAD  50  received for individual ones of those users, and, optionally, for providing individualized feedback to such users. User feedback includes, for example, statistical and/or graphical analyses of the user&#39;s PAD  50 , historical PAD data, e.g., tracked over one or more intervals of time. Additionally or alternatively, the online computer system  60  uses the PAD  50  received for a given user to determine personalized health, fitness and/or lifestyle recommendations to the user. Such recommendations include, for example, recommended activities, diet or food recommendations, exercise equipment recommendations, etc. 
         [0037]    In the illustrated example, the online computer system  60  includes network (NW) interface circuitry  62 , which in at least some embodiments provides web server functionality, e.g., for use by the app  48  in some of its embodiments and/or for browser-based access via the communication devices  40  or personal computers (not shown). The online computer system  60  further includes a processing circuit  64 —e.g., any one or more microprocessor-based circuits—and associated storage  66 . 
         [0038]    The storage  66  comprises one or more types of non-transitory computer readable medium and in an example configuration provides storage for a computer program  68 , the execution of which configures the online computer system  60  according to the teachings herein. The storage  66  further stores user accounts  70 , including user-specific PAD  72 . The PAD  72  in a given user account  70  comprises, for example, comprises a full or partial copy of the PAD  50  stored in the user&#39;s corresponding communication device  40 , or comprises data derived or otherwise aggregated therefrom, e.g., accumulated data, averaged data, data representing activity levels over time, etc. 
         [0039]    Thus, it will be appreciated that the PAD  72  for each user account  70  comprises PAD  50  collected from the respective user&#39;s communication device  40  and/or data derived therefrom. In turn, the PAD  50  for a given user comprises PAD  20  collected from the user&#39;s tracker  10  and/or data derived therefrom. 
         [0040]      FIG. 1  further illustrates that the tracker  10 , as a wearable electronic device, may be configured for detachably integrating with a bracelet  80 , for convenient wearability. Further, the tracker  10  may be associated with a charging station  90 . To better understand example attributes of the tracker  10 , the bracelet  80  and the charging station  90 ,  FIGS. 2-4  provide several perspective views of the tracker  10  in one or more embodiments. 
         [0041]      FIG. 2  in particular illustrates that the display  24  of the tracker  10  may be mounted behind a transparent region  100  in an upper surface of a tracker housing  102 , such that illuminated portions of the display  24  are visible through the tracker housing  102 . In some embodiments, the transparent region  100  is tinted or otherwise treated so that it exhibits an opaque appearance but does not prevent impair legibility of the display  24  when the display  24  is illuminated. Further, particularly where the transparency of the tracker housing  102  is not discernable in the absence of back illumination, all or at least the top half of the tracker housing  102  may be transparent. 
         [0042]    In any case, it will be appreciated that the example tracker housing  102  includes opposing exterior top and exterior bottom surfaces, opposing exterior side surfaces along the long axis of the tracker housing  102 , and opposing exterior end surfaces along the short axis of the tracker housing. In this regard,  FIG. 2  also illustrates an example, advantageous positioning of the touch sensor  28 -A along one of the side surfaces defined by the long-axis of the tracker  10 . The region of the exterior surface overlaying the touch sensor  28 -A thus functions as a corresponding touch point  104 -A. It will be appreciated that in this embodiment the other touch sensor  28 -B is positioned within the interior of the tracker housing  102  such that its corresponding touch point  104 -B is symmetrically positioned on the opposing exterior surface of the tracker housing  102 , such as seen in  FIGS. 3 and 4 . 
         [0043]    The use of underlying touch sensors  28 -A and  28 -B avoids the need for openings in the tracker housing  102 —i.e., the touch sensors  28 -A and  28 -B are operative to sense touch through the tracker housing  102  and can thus be located inside the housing. Further, by physically separating the touch points  104 -A and  104 -B—e.g., by positioning them on opposing sides or ends of the tracker housing  102 —the touch interface of the tracker  10  is essentially insusceptible to accidental activation by the user. Instead, to make a control input to the tracker  10  via the tracker&#39;s touch interface, the user must simultaneously touch the two physically separated touch points  104 -A and  104 -B on the exterior of the tracker housing  102 . 
         [0044]    A “pinching” gesture, e.g., involving the user&#39;s thumb and forefinger, represents a convenient control gesture for simultaneously contacting two touch points  104 -A and  104 -B having significant physical separation, whether such separation is achieved by spacing the touch points  104 -A and  104 -B at separate locations on the same surface, or is achieved by locating the touch points  104 -A and  104 -B on opposing exterior surfaces of the tracker housing  102 . Thus, the dual-touch input required by the tracker  10  is also referred to as a “pinch” input, and, likewise, a detected dual-touch event may also be referred to as a “pinch event.” However, unless otherwise noted the terms “pinch” and “pinch event” are not meant to imply that the tracker  10  performs pressure or force sensing at the touch points  104 -A and  104 -B. 
         [0045]    Further, it should be understood that one or more embodiments contemplated herein maintain physical separation of the touch points  104 -A and  104 -B without necessarily locating them on opposing sides or surfaces of the tracker housing  102 . Thus, while opposing-surface positioning of the touch points  104 -A and  104 -B is preferred for some tracker form factors, it is also contemplated herein to simply provide sufficient physical separation between the touch points  104 -A and  104 -B to effectively eliminate the possibility of accidental simultaneous contact by the user with both touch points  104 -A and  104 -B. 
         [0046]    It is also contemplated that there may be more than two touch points  104 , where the “ 104 ” designation is used generically to refer to any one or more touch points  104  implemented via corresponding touch sensors  28 . For example, there may be a first touch point  104  that is common to two or more other touch points  104 . The user thus inputs different commands depending on which touch-point pairing she chooses, from among the possible pairings. A set of three such touch points  104  in that configuration yield two distinct pairings while a set of four touch points  104  with one being common to the other three yields three distinct pairings. 
         [0047]    Regardless, in a non-limiting example of the contemplated touch sensing, the touch sensors  28 -A and  28 -B are implemented as a pair of electrodes, with each electrode positioned underneath the exterior surface of the tracker housing  102  at a respective one of the touch points. Correspondingly, the touch circuit  26  comprises sensing circuitry configured to sense a change in capacitance between the electrode pair, such as occurs when the user simultaneously contacts the exterior surface of the tracker housing  102  at the two touch points  104  corresponding to the electrode pair. In a non-limiting example, the touch circuit  26  comprises an MPR031EPR2 integrated circuit (IC). The MPR031EPR2 IC is a proximity capacitive touch sensor controller from FREESCALE SEMICONDUCTOR, INC., and it is configured to “drive” an attached electrode pair and correspondingly sense changes in capacitance between the electrodes. 
         [0048]    In addition to illustrating the touch sensor  28 -B and its corresponding touch point  104 -B on the depicted side of the tracker housing  102 ,  FIG. 3  depicts a mechanical clip assembly  110 . The clip assembly  110  is implemented on a bottom side of the tracker housing  102  and enables the tracker  10  to be clipped to a user&#39;s clothing, for example. 
         [0049]      FIG. 4  illustrates additional bottom-side features of the tracker  10 . The illustrated features include a number of charging contacts  122 , along with magnetic attachment points  124  that removably “attach” the tracker  10  to a charging station, such as the example charging station  90  shown in  FIG. 5 . One also sees that the various structural elements of the clip assembly  110  surround but do not cover or otherwise block access to the contacts  122  and attachment points  124 . 
         [0050]    The charging station  90  includes electrical contacts  92  that mate with and correspond to the electrical contacts  122  on the bottom side of the tracker housing  102 . The charging station  90  further includes attachment contacts  94  to magnetically couple to the magnetic contacts  124  on the bottom side of the tracker housing  102 . 
         [0051]    More particularly, in an example embodiment, the tracker housing  102  is configured to mount or otherwise snap into a receptacle portion  82  of a bracelet  80 , such as shown in  FIGS. 6 and 7 . Correspondingly, the body portion of the charging station  90  that carries the contacts  92  and  94  is dimensioned for encirclement by the bracelet  80 . 
         [0052]    In more detail, the tracker housing  102  is contoured and dimensioned to complement the size and shape of the receptacle portion  82  of the bracelet  80 , such that it at least partially seats into the receptacle portion  82 . The receptacle portion  82  may include within it mating features  84 -A and  84 -B that are configured to mate with engaging surfaces or elements of the clip assembly  110  on the bottom of the tracker housing  102 . Further in this embodiment, the touch sensors  28 -A and  28 -B are positioned within the interior of the tracker housing  102  so that the corresponding touch points  104 -A and  104 -B are accessible along the side surfaces of the tracker  10  when it is fully seated into the receptacle portion of the bracelet  82 . 
         [0053]    As noted, the charging station  90  is dimensioned so that the bracelet  80  can slip over or around the body of the charging station  90  at the point where the electrical and magnetic contacts  92  and  94  of the charging station  90  are located. This configuration allows the tracker  10  to be mounted in the bracelet  80 , thereby forming a tracker/bracelet assembly, which in turn mounts to the charging station  90 . 
         [0054]    It will be understood that the open bottom of the receptacle portion  82 , as seen in  FIG. 6 , leaves the electrical and magnetic contacts  122  and  124  of the tracker  10  exposed, for coupling to the electrical and magnetic contacts  92  and  94  of the charging station  90 . Thus, the bracelet  80  serves as a carrier for the tracker  10  and not only provides an aesthetic mechanism for wearing but further facilitates mounting the tracker  10  to the charging station  90 , for charging. 
         [0055]      FIG. 8  illustrates a more detailed example embodiment of the tracker  10 . With simultaneous reference to  FIG. 1 , the communication interface  12  may comprise a BLUETOOTH interface  202 , such as may be implemented using a DA14580-01UNA IC from Dialog Semiconductor. The processing circuit  14  may be implemented using an ultra-low power processor, such as an STM32L processor provided by STMICROELECTRONICS and targeted for use in so called “wearable” applications. 
         [0056]    Further, one sees that the storage  16  may be implemented using an EEPROM device  206  and that the touch circuit  26  and touch sensors  28 -A and  28 -B may be implemented using a touch-sensing IC coupled to a corresponding pair of electrodes  210  and  212 . Additionally, the display  24  may be implemented as an OLED display unit  214 , along with the motion sensor  30  being implemented as a low-power MEMS-type accelerometer, such as an ADXL362 IC from ANALOG DEVICES. Similarly, the altimeter  32  may be implemented using a low-power barometric sensor  216 , such as a MEMS-based pressure sensor like the LPS331AP IC from STMICROELECTRONICS. In an advantageous alternative used in one or more other embodiments of the tracker  10 , the motion sensor  30  and the altimeter  32  are implemented together in a low-power ASIC. 
         [0057]    The tracker  10  in the illustrated example includes further miscellaneous circuits or items, including a Lithium-Polymer (Li-Po) battery  220 , along with a charging circuit  222  and a protection circuit  224  that couples the Li-Po battery  220  to one or more DC/DC converters and associated control logic  226  and  228 , for powering the OLED display  214  and the processing circuit  214  and its associated circuitry, such as reset circuit  230  and a motor driver  232  and motor  234  (to provide the tracker  10  with a vibrate function). 
         [0058]    Regardless of its implementation details and the specific component types used in the tracker  10 , the tracker  10  in at least some embodiments is configured to provide a relatively rich set of capabilities and to operate in various modes that provide power savings and intuitive user operation. In a “deep sleep” mode of the tracker  10 , all sensors are off, and the tracker  10  operates in its lowest possible power state. 
         [0059]    In at least one embodiment, the communication interface  12  shown in  FIG. 1  implements a serial communication interface using the electrical contacts  122  provided on the bottom of the tracker housing  102 . Correspondingly, the processing circuit  14  places the tracker  10  in the deep sleep mode in response to receiving a defined command via the serial interface. Additionally or alternatively, the processing circuit  14  places the tracker  10  in the deep sleep mode in response to receiving the deep sleep command via a BLUETOOTH or other wireless interface implemented via communication interface  12 . 
         [0060]    The processing circuit  14  exits the deep sleep mode responsive to detecting that the tracker  10  has been placed on the charging station  90 . For example, the tracker  10  transitions from the deep sleep mode to a “normal” mode in response to being placed on the charging station  90 . If while in normal mode the tracker  10  is not “connected” to a user&#39;s communication device  40 , the tracker  10  advertises its presence via the communication interface  12 , e.g., it sends periodic BLUETOOTH or other personal area network signaling. The current “step count” for the day may be included in the advertising data. Here, “step count” is the number of steps taken by the user, as computed by the tracker  10  based on detecting or otherwise processing output signaling from the motion sensor  30 . The tracker  10  may further store stride length information for the user as part of the configuration data  22 , for use in more accurately computing steps or determining corresponding distances traveled. 
         [0061]    The configuration data  22  also may include factory-installed data, such as a password or other “key” that must be received from any communication device  40  attempting to pair with or otherwise communicate with the tracker  10 . Even if not used to authenticate all communications, the password or other stored key may be required for key operations, such as updating firmware, etc. Of course, the password-based authentication may be transparent to the user. For example, the user purchases a tracker  10  that contains a factory-loaded password. When the user registers her tracker  10  with the online computer system  60 , the online computer system  60  maps the serial number of the tracker  10  to the preloaded password and sends that password to the instance of the app  48  that is installed in the user&#39;s communication device  40 . 
         [0062]    In another embodiment, the password in the tracker  10  is initially set to 0 (zero). When an instance of the app  48  running on the user&#39;s communication device  40  wants to pair with the tracker  10 , it uses the default password to make initial contact and then generates a new password, e.g., via a random number generator function, and the provides it to the tracker  10  as the new password. The tracker  10  replaces the default password with the new password. Performing a device reset on the tracker  10  resets to the tracker  10  to the default password, which allows the user a convenient recovery mechanism and allows the tracker  10  to be paired with a new communication device  40 . 
         [0063]    Additional aspects of the tracker&#39;s operation in one or more embodiments are detailed in  FIG. 9 , which depicts a method  900  that is implemented, e.g., by the processing circuit  14  based on its execution of stored computer program instructions from the computer program  18  held in the storage  16 . It will be appreciated that the “start” and “end” labels in the illustrated flow do not preclude the possibility of looping or otherwise repeatedly performing the depicted processing, nor the possibility that the depicted processing is performed in conjunction with other operations, or as part of an overall processing routine. 
         [0064]    Processing according to the example flow diagram begins with “monitoring” the touch interface of the tracker  10  (Block  902 ). Here, monitoring may be passive, in the sense that a low power touch IC  208 , such as shown in  FIG. 8 , is configured to detect the change in capacitance resulting from a dual-touch event. Upon detecting a dual-touch (“pinch”) event (YES from Block  904 ), the tracker  10  starts a “pinch” timer (Block  906 ) that times the duration of the pinch event. 
         [0065]    The tracker  10  further determines whether or not it is mounted on the charging station  90  (Block  908 ). The determination can be made based upon the processing circuit  14  sensing the presence of an input charging voltage, or it can be sensed, e.g., using a discrete input signal that is pulled high or low when the tracker  10  is mounted to the charging station  90 , e.g., sensed as a consequence of magnetic or electrical coupling with the charging station  90 . 
         [0066]    If the tracker  10  determines that it is on the charging station  90  (YES from Block  908 ), it displays the current battery level (Block  910 ). Displaying the battery level may be a timed operation, e.g., the level is displayed for five seconds by default. However, the tracker  10  senses whether the user&#39;s pinch continues (Block  912 ). If the pinch persists for 10 seconds (YES from Block  914 ), the tracker performs reset processing (Block  916 ) as described below. 
         [0067]    In at least one embodiment of reset processing, the user performs a device reset by placing the tracker  10  on the charging station  90 , with the charging station plugged into an appropriate source of mains power. The user then simultaneously touches both touch sensors  28 -A and  28 -B and holds that contact for ten (10) seconds. In other words, the user performs a “dual touch” or “pinch” operation of ten seconds in duration. Here, a “dual touch” or “pinch” operation means that the user simultaneously touches the tracker housing  102  at the two touch points on the exterior of the tracker housing  102  corresponding to the touch sensors  28 -A and  28 -B. At the ten-second mark, the tracker  10  displays the phrase “RESET?” or some equivalent reset prompt for the user. If the user then releases the pinch within five (5) seconds after the tracker  10  displays the reset prompt, the tracker  10  performs the reset operation. Otherwise, the reset operation is not performed, and the tracker  10  in one or more embodiments displays a corresponding message to the user. 
         [0068]    Broadly, when the tracker  10  is operating in its “normal” mode and is placed on the charging station  90 , it cycles through a set of battery level icons or values on its display  24 , e.g., 0%, 25%, 50%, 75%, 100% . . . , for ten seconds. Further, when the tracker  10  is on the charging station  90  and reaches a full charge, it uses its display  24  to display a 100% charge battery level reading or icon. And, as noted, the tracker  10  displays its current charge state for five seconds if the user pinches the tracker  10  while it is charging. The tracker  10  may also display a charging animation to inform the user that charging is underway. Also, as noted, if the pinch persists for ten seconds while the tracker  10  is charging, the tracker  10  will prompt to see if the user wishes to perform a device reset. 
         [0069]    As for the behavior of the tracker  10  when it is pinched while not being charged (“NO” from Block  908 ), processing continues with displaying the current primary metric, e.g., the current day&#39;s step count (Block  918 ). Such processing may be based on displaying the current primary metric on a timed basis, e.g., for a default period and then shutting the display  14  off unless the pinch persists (Block  920 ). If the pinch is released before the pinch timer reaches three seconds (see Blocks  920  and  922 ), the tracker  10  performs its normal-mode short-pinch processing (Block  924 ). In one implementation, the primary metric display at Block  918  lasts three seconds and, if the pinch is released before the pinch timer reaches the three-second mark, the tracker  10  performs short-pinch processing by displaying the time of day for five seconds and then turning off. 
         [0070]    Conversely, if the pinch persists for at least three seconds (YES from Block  922 ), the tracker  10  performs its normal-mode long-pinch processing ( 926 ). In an example case, if the pinch is held for more than three seconds, the tracker  10  uses its display  24  to continuously cycle through all of its defined primary metrics, with each metric displaying in turn for one second. If the user releases the pinch while the tracker  10  is cycling through the primary metrics in this manner, the tracker  10  will continue to display the last displayed metric for a further three seconds and then turn off. 
         [0071]    Further, the method  900  may be extended to include a flight mode. Assuming that a pinch event has occurred and assuming that the tracker  10  is not on-charger (NO from Block  908 ) and is in its normal operating mode, the tracker  10  uses its pinch timer to detect whether or not the detected pinch persists for thirty (30) seconds. If so, the tracker  10  enters an “airplane” mode in which it turns off radio communications. If the tracker  10  detects another thirty-second pinch while in the airplane mode, the tracker  10  exits the airplane mode and returns to its normal mode of operation. The tracker  10  in at least one embodiment uses its display  24  to inform the user of its entry into and exit from the airplane mode. 
         [0072]      FIG. 10  illustrates that the clip assembly  110  in one or more embodiments includes an external clip  300  and a stem assembly  302  that anchors the external clip  300  to an internal spring  304 , as seen in the cutaway views provided in  FIGS. 11 and 12 . As seen in these latter two figures, the stem assembly  302  may comprise multiple parts and it may be fabricated from steel or other metal, or from plastic (such as a fiber-reinforced plastic), or from some mix of materials. For example, in  FIG. 12 , one sees that the stem assembly  302  includes first and second body members  310  and an inner retaining member  312 . 
         [0073]    In one example configuration, the body members  310  are a fiber-reinforced plastic material and the inner retaining member  312  is steel or another metal. Use of plastics or other non-conductive materials for the body members  310  and/or the inner retaining member  312  provides, for example, enhanced protection against Electrostatic Discharge (ESD) for the tracker&#39;s internal circuitry. 
         [0074]      FIG. 13  illustrates an embodiment of the clip assembly  110  in more detail, where the assembly is shown divorced from the tracker  10  for improved clarity. Again, one sees the external clip  300 , which is joined to the internal spring  304  via the stem assembly  302 . It will be appreciated that internal features within the tracker housing  102  fixedly retain the internal spring  304  and/or stem assembly  302  for the proper operation of the clip assembly  110 . 
         [0075]      FIGS. 14A and 14B  provide an example of such operation.  FIG. 14A  illustrates the tracker  10  in a side view and one sees that the clip assembly  110  is in its closed position. It will be appreciated that the clip assembly  110  may be resiliently biased into its closed position via the spring force created by its construction. In particular, note that a retaining post or feature  320  within the interior of the tracker housing  102  prevents the internal spring  304  from moving downward in sympathy with the external clip  300 , as clothing or some other item  322  is slid in between the bottom side of the tracker housing  102  and the external clip  300 . This arrangement provides for a degree of movement by the stem assembly  302 , which allows the clip assembly  110  to clip to items  322  of a wider range of thicknesses, while not compromising the spring force (clipping strength) of the clip assembly  110 . 
         [0076]    Notably, modifications and other embodiments of the disclosed invention(s) will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. For example, the dual-touch event timings used herein for differentiating between control actions, and other dual-touch timing values may be varied from the values given herein. 
         [0077]    It is recognized herein that the disclosed configuration of an electronic device for tracking physical activity particularly benefits from the dual-touch circuitry and related operation, e.g., in view of the device&#39;s intended use on or in close proximity to a user&#39;s body, in view of which portions of the device&#39;s housing are accessible when worn by the user and in view of the need for robust and reliable control in wearable device usage scenarios. However, it shall be understood that the teachings herein apply to other type of electronic devices or apparatuses. Thus, the use of dual touch points on an exterior housing and the implementation of corresponding touch detection circuitry and control algorithms supporting dual-touch control may find advantageous use in a broad range of electronic devices or apparatus having varied uses or purposes. The teachings herein are therefore not limited to wearable electronic devices used for tracking the physical activity of a user. 
         [0078]    In general, it is to be understood that the invention(s) is/are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. 
         [0079]    Notably, modifications and other embodiments of the disclosed invention(s) will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention(s) is/are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.