PATENT DOCUMENT

Publication Number: US-9811204-B2
Application Number: US-201414312437-A
Country: US
Kind Code: B2

Title: Time multiplexed touch detection and power charging

Abstract:
A method of scanning a touch sensor panel while the touch sensor panel is coupled to a power adapter is disclosed. The power adapter can charge a battery of a device, but can also introduce or add noise during the process of charging the battery. To prevent adverse effects to the touch sensor panel, while the device is charging, the touch controller can time multiplex touch scan periods and inductive charging periods and can discard touch scans or touch images affected by the noise. Determining whether a touch scan is a bad touch scan can include performing a touch scan across the array of touch pixels and making a determination based on the scan profile. In some examples, the profile can be quantified using different metrics such as the shape, instantaneous slope of tail ends, a full-width half-maximum, and a monotonicity of the curve of the scan profile.

Claims:
What is claimed is: 
     
       1. A method of scanning a touch sensor panel, comprising:
 acquiring touch data from a plurality of touch sensors during at least one of charge and charge-free periods, the charge and charge-free periods occurring while the touch sensor panel is coupled to a charger; 
 determining whether the touch data was acquired during at least one of the charge periods, wherein the at least one of the charge periods includes noise received from the charger; 
 discarding the touch data when the touch data was acquired during the at least one of the charge periods; 
 in accordance with the touch data including an indication of a touch on the touch sensor panel:
 generating and transmitting a first notification to the charger to operate with charge periods having a first duty cycle; and 
 
 in accordance with the touch data including an indication of an absence of a touch on the touch sensor panel:
 generating and transmitting a second notification to the charger to operate with charge periods having a second duty cycle, the second duty cycle greater than the first duty cycle. 
 
 
     
     
       2. The method of  claim 1 , wherein the determination of whether the touch data was acquired during at least one of the charge periods further includes:
 comparing at least a portion of the touch data to a capacitance value from at least one of the plurality of touch sensors, wherein the at least a portion of the touch data is associated with the at least one of the plurality of touch sensors. 
 
     
     
       3. The method of  claim 1 , wherein the plurality of touch sensors are incorporated into a first device, the method further comprising:
 sending, to a second device, external to the first device, the acquired touch data; and 
 receiving, from the second device, at least one of a noise-free touch image, scan period, and a number of touch scans within a scan period associated with the acquired touch data. 
 
     
     
       4. The method of  claim 1 , wherein:
 the first duty cycle is based on a touch sensing duty cycle of the touch sensor panel. 
 
     
     
       5. The method of  claim 1 , wherein the determination of whether the touch data was acquired during at least one of the charge periods includes:
 determining a curve of a touch profile from the acquired touch data; 
 determining a shape of the curve; and 
 comparing the shape of the curve to a shape of a historical touch profile. 
 
     
     
       6. The method of  claim 5 , wherein the curve is a Gaussian curve. 
     
     
       7. The method of  claim 5 , wherein the determination of whether the touch data was acquired during at least one of the charge periods further includes:
 one or more of determining a slope of the curve and using the slope in the comparison, and determining a full-width half-maximum of the curve. 
 
     
     
       8. The method of  claim 1 , further comprising determining a number of scans including the touch data acquired during the charge-free periods. 
     
     
       9. The method of  claim 8 , further comprising dynamically changing at least one of a scan period, a scan frequency, and a number of touch scans within the scan period based on the determined number of scans acquired during the charge-free periods. 
     
     
       10. A touch sensor panel comprising:
 sensing circuitry configured to acquire touch data from a plurality of touch sensors during at least one of the charge and charge-free periods, the charge and charge-free periods occurring while the touch sensor panel is coupled to a charger; and 
 a processor configured to:
 determine whether the touch data was acquired during at least one of the charge periods, wherein the at least one of the charge periods includes noise generated by the charger; 
 discard the touch data when the touch data was acquired during the at least one of the charge periods; 
 in accordance with the touch data including an indication of a touch on the touch sensor panel:
 generate and transmit a first notification to the charger to operate with charge periods having a first duty cycle; and 
 
 in accordance with the touch data including an indication of an absence of a touch on the touch sensor panel:
 generate and transmit a second notification to the charger to operate with charge periods having a second duty cycle, the second duty cycle greater than the first duty cycle. 
 
 
 
     
     
       11. The touch sensor panel of  claim 10 , wherein the touch sensor panel is configured with a duty cycle of scan periods greater than or equal to a duty cycle of charge periods of the charger when the touch sensor panel is coupled to the charger. 
     
     
       12. The method of  claim 10 , wherein:
 the first duty cycle is based on a touch sensing duty cycle of the touch sensor panel. 
 
     
     
       13. The touch sensor panel of  claim 10 , wherein the processor is further configured to determine a curve of a touch profile from the acquired touch data, determine a shape of the curve, and compare the shape of the curve to a shape of a historical touch profile. 
     
     
       14. The touch sensor panel of  claim 13 , wherein the historical touch profile includes a predetermined curve. 
     
     
       15. The touch sensor panel of  claim 13 , wherein the processor is further configured to:
 perform one or more operations of determining a slope of the curve used for the comparison and determining a full-width half-maximum of the curve. 
 
     
     
       16. The touch sensor panel of  claim 10 , wherein the processor is further configured to determine a number of scans including the touch data acquired during the charge-free periods. 
     
     
       17. The touch sensor panel of  claim 16 , wherein the processor is further configured to dynamically change at least one of a scan period, a scan frequency, and a number of touch scans within the scan period based on the determined number of scans acquired during the charge-free periods. 
     
     
       18. A method of charging a touch sensor panel with a charger, the method comprising:
 receiving a first notification from the touch sensor panel, wherein the first notification includes an indication of a touch on the touch sensor panel; 
 in accordance with receiving the first notification, operating the charger with charge periods having a first duty cycle, the first duty cycle less than a duty cycle of a scan period of the touch sensor panel; 
 receiving a second notification from the touch sensor panel, wherein the second notification includes an indication of an absence of a touch occurring on the touch sensor panel; and 
 in accordance with receiving the second notification, operating the charger with charge periods having a second duty cycle, the second duty cycle greater than the first duty cycle.

Description:
FIELD OF THE DISCLOSURE 
     This relates generally to touch sensitive devices, and in particular, to a touch scan mode during device charging. 
     BACKGROUND OF THE DISCLOSURE 
     Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, touch sensor panels, joysticks, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface. The touch sensor panel can be positioned in front of a display screen so that the touch-sensitive surface covers the viewable area of the display screen. Touch screens can allow a user to make selections and move a cursor by simply touching the display screen via a finger or stylus. In general, the touch screen can recognize a touch and position of the touch on the display screen, the computing system can interpret the touch, and thereafter, perform an action based on the touch event. 
     One limitation of touch sensor panel technologies is that noise can adversely affect the performance of a touch sensor panel device. Noise from sources such as a power adapter or an inductive charger can influence the results of a touch sensor panel device. For example, the touch sensor panel device can be coupled to a power adapter or inductive charger to charge a battery on the device. The charger can introduce noise while charging, which can prevent a touch sensor panel from distinguishing between a touch event (e.g., a user&#39;s contact of a touch sensor panel) and noise influencing the sensors of the touch sensor panel. 
     SUMMARY 
     This relates to time multiplexed touch detection and power charging of touch sensitive devices. A power adapter or an inductive charger can charge a battery of a device, but can also introduce or add noise during the process of charging the battery. Touch pixels of a touch sensitive device can be stimulated by noise from the charger, and can adversely affect one or more components, such as the touch sensor panel. To prevent adverse effects to the touch sensor panel, while the device is charging, the touch controller can time multiplex touch scan periods and inductive charging periods and can discard touch scans or touch images affected by the noise. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1C  illustrate systems in which examples of the disclosure can be implemented. 
         FIG. 2  illustrates an exemplary computing system utilizing the one or more time multiplexing methods according to various examples of the disclosure. 
         FIG. 3A  illustrates an exemplary mutual capacitance touch sensor panel according to examples of the disclosure. 
         FIG. 3B  illustrates a side view of an exemplary pixel in a steady-state (no-touch) condition according to examples of the disclosure. 
         FIG. 3C  illustrates a side view of an exemplary pixel in a dynamic (touch) condition according to examples of the disclosure. 
         FIG. 4A  illustrates an exemplary touch sensor circuit corresponding to a self-capacitance touch pixel electrode and sensing circuit according to examples of the disclosure. 
         FIG. 4B  illustrates an exemplary self-capacitance touch sensor panel according to examples of the disclosure. 
         FIG. 5  illustrates an exemplary configuration of a device coupled to a charger according to examples of the disclosure. 
         FIG. 6A  illustrates an exemplary touch scan while a device is not charging. 
         FIG. 6B  illustrates an exemplary touch scan affected by noise from a charger according to examples of the disclosure. 
         FIG. 6C  illustrates an exemplary time multiplexed touch detection and power charging according to examples of the disclosure. 
         FIG. 7A  illustrates an exemplary time multiplexed touch detection and power charging according to examples of the disclosure. 
         FIG. 7B  illustrates a process for an exemplary time multiplexed touch detection and power charging according to examples of the disclosure. 
         FIG. 8A  illustrates a touch scan profile of a noise-free touch image according to examples of the disclosure. 
         FIG. 8B  illustrates a touch scan profile of a touch image affected by noise according to examples of the disclosure. 
         FIG. 9  illustrates an exemplary configuration in which a device is connected to a host 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. 
     Various techniques and process flow steps will be described in detail with reference to examples as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects and/or features described or referenced herein. It will be apparent, however, to one skilled in the art, that one or more aspects and/or features described or referenced herein may be practiced without some or all of these specific details. In other instances, well-known process steps and/or structures have not been described in detail in order to not obscure some of the aspects and/or features described or referenced herein. 
     Further, although process steps or method steps can be described in a sequential order, such processes and methods can be configured to work in any suitable order. In other words, any sequence or order of steps that can be described in the disclosure does not, in and of itself, indicate a requirement that the steps be performed in that order. Further, some steps can be performed simultaneously despite being described or implied as occurring non-simultaneously (e.g., because one step is described after the other step). Moreover, the illustration of a process by its depiction in a drawing does not imply that the illustrated process is exclusive of other variations and modification thereto, does not imply that the illustrated process or any of its steps are necessary to one or more of the examples, and does not imply that the illustrated process is preferred. 
     Touch-sensitive screens (“touch screens” or “touchscreens”) can be used in many electronic devices to display graphics and text and to provide a user interface through which a user can interact with the devices. A touch screen can detect and respond to contact on the touch screen. A device can display one or more soft keys, menus, and other user-interface objects on the touch screen. A user can interact with the device by contacting the touch screen at locations corresponding to the user-interface object with which the user wishes to interact. 
     This disclosure relates to time multiplexed touch detection and power charging of touch sensitive devices. A power adapter or inductive charger can charge a battery of a device, but can also introduce or add noise during the process of charging the battery. Inductive charging can introduce a significant amount of noise due to the extremely strong carrier signal during the charging time. Touch pixels of a touch sensitive device can be stimulated by noise from the power adapter or inductive charger, and can adversely affect one or more components, such as the touch sensor panel. To prevent adverse effects to the touch sensor panel, while the device is charging, the touch controller can time multiplex touch scan periods and inductive charging periods and can discard touch scans or touch images affected by the noise. 
       FIGS. 1A-1C  illustrate systems in which examples of the disclosure can be implemented.  FIG. 1A  illustrates an exemplary mobile telephone  136  that can include a touch screen  124 .  FIG. 1B  illustrates an exemplary media player  140  that can include a touch screen  126 .  FIG. 1C  illustrates an exemplary wearable device  144  that can include a touch screen  128  and can be attached to a user using strap  146 . The systems of  FIGS. 1A-1C  can utilize the one or more time multiplexing methods, as will be disclosed. 
       FIG. 2  illustrates an exemplary computing system utilizing the one or more time multiplexing methods according to various examples of the disclosure. Computing system  200  can be included in any electronic device such as the one or more exemplary devices illustrated in  FIGS. 1A-1C . Touch controller  206  can be a single application specific integrated circuit (ASIC) that can include one or more processor subsystems such as processor subsystem  202 , which can include, for example, one or more main processors, such as ARM968 processors or other processors with similar functionality and capabilities. However, in other examples, some of the processor functionality can be implemented instead by dedicated logic, such as a state machine. Processor subsystem  202  can also include, for example, peripherals such as random access memory (RAM)  212  or other types of memory or storage, watchdog timers (not shown), and the like. Touch controller  206  can also include, for example, receive section  207  for receiving signals, such as touch sense signals  203 , from the sense lines of touch sensor panel  224 , and other signals from other sensors such as sensor  211 , etc. Touch controller  206  can also include, for example, a demodulation section  209 , panel scan logic  210 , and a drive system including, for example, transmit section  214 . Panel scan logic  210  can access RAM  212 , autonomously read data from the sense channels, and provide control for the sense channels. In addition, panel scan logic  210  can control transmit section  214  to generate stimulation signals  216  at various frequencies and phases that can be selectively applied to the drive lines of the touch sensor panel  224 . 
     Charge pump  215  can be used to generate the supply voltage for the transmit section. Stimulation signals  216  (Vstim) can have amplitudes higher than the maximum voltage the ASIC process can tolerate by cascading transistors. Therefore, using charge pump  215 , the stimulus voltage can be higher (e.g., 6V) than the voltage level a single transistor can handle (e.g., 3.6 V). Although  FIG. 2  shows charge pump  215  separate from transmit section  214 , the charge pump can be part of the transmit section. 
     Touch sensor panel  224  can include a capacitive sensing medium having a plurality of drive lines and a plurality of sense lines. The drive and sense lines can be formed from a transparent conductive medium such as Indium Tin Oxide (ITO) or Antimony Tin Oxide (ATO), although other transparent and non-transparent materials such as copper can also be used. In some examples, the drive and sense lines can be perpendicular to each other, although in other examples other non-Cartesian orientations are possible. For example, in a polar coordinate system, the sensing lines can be concentric circles and the driving lines can be radially extending lines (or vice versa). It should be understood, therefore, that the terms “drive lines” and “sense lines” as used herein are intended to encompass not only orthogonal grids, but the intersecting traces or other geometric configurations having first and second dimensions (e.g., the concentric and radial lines of a polar-coordinate arrangement). The drive and sense lines can be formed on, for example, a single side of a substantially transparent substrate. 
     At the “intersections” of the traces, where the drive and sense lines can pass adjacent to and above and below (cross) each other (but without making direct electrical contact with each other), the drive and sense lines can essentially form two electrodes (although more than two traces could intersect as well). Each intersection of drive and sense lines can represent a capacitive sensing node and can be viewed as touch pixel or node  226 , which can be particularly useful when touch sensor panel  224  is viewed as capturing an “image” of touch. (In other words, after touch controller  206  has determined whether a touch event has been detected at each touch sensor in the touch sensor panel, the pattern of touch sensors in the multi-touch sensor panel at which a touch event occurred can be viewed as an “image” of touch (e.g., a pattern of fingers touching the panel.) The capacitance between drive and sense electrodes can appear as stray capacitance when the given row is held at direct current (DC) voltage levels and as a mutual capacitance Csig when the given row is stimulated with an alternating current (AC) signal. The presence of a finger or other object near or on the touch sensor panel can be detected by measuring changes to a signal charge Qsig present at the pixels being touched, which is a function of Csig. 
     Computing system  200  can also include host processor  228  for receiving outputs from processor subsystem  202  and performing actions based on the outputs that can include, but are not limited to, moving an object such as a cursor or pointer, scrolling or panning, adjusting control settings, opening a file or document, viewing a menu, making a selection, executing instructions, operating a peripheral device connected to the host device, answering 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  228  can perform additional functions that may not be related to panel processing, and can be coupled to program storage  232  and display  230 , such as an LCD display, for providing a user interface to a user of the device. In some examples, host processor  228  can be a separate component from touch controller  206 , as shown. In some examples, host processor  228  can be included as part of touch controller  206 . In some examples, the functions of host processor  228  can be performed by processor subsystem  202  and/or distributed among other components of touch controller  206 . Display  230  together with touch sensor panel  224 , when located partially or entirely under the touch sensor panel  224 , can form touch screen  218 . 
     Note that one or more of the functions described above can be performed, for example, by firmware stored in memory (e.g., one of the peripherals) and executed by processor subsystem  202 , or stored in program storage  232  and executed by host processor  228 . The firmware can also be stored and/or transported within any non-transitory computer-readable storage medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “non-transitory computer-readable storage medium” can be any medium (excluding a signal) that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device. The non-transitory computer readable 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 as 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 be propagated within any transport medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “transport medium” can be any medium that can communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The transport readable medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, or infrared wired or wireless propagation medium. 
       FIG. 3A  illustrates an exemplary mutual capacitance touch sensor panel according to examples of the disclosure. Stray capacitance Cstray can be present at each pixel  302  located at the intersection of a row  304  and a column  306  trace (although Cstray for only one column is illustrated in  FIG. 3A  for purposes of simplifying the figure) of touch sensor panel  330 . In the example of  FIG. 3A , AC stimuli Vstim  314 , Vstim  315  and Vstim  317  can be at different frequencies and phases. Each stimulation signal on a row can cause a charge Qsig=Csig×Vstim to be injected into the columns through the mutual capacitance present at the affected pixels. A change in the injected charge (Qsig_sense) can be detected when a finger, palm or other object is present at one or more of the affected pixels. Vstim signals  314 ,  315  and  317  can include one or more bursts of sine waves. Note that although  FIG. 3A  illustrates rows  304  and columns  306  as being substantially perpendicular, they need not be aligned, as described above. As described above, each column  306  can be connected to a receive channel such as receive section  207  of  FIG. 2 . 
       FIG. 3B  illustrates a side view of an exemplary pixel in a steady-state (no-touch) condition according to examples of the disclosure. In  FIG. 3B , electric field lines  308  between a column trace  306  and a row trace  304  separated by dielectric  310  is shown at pixel  302 . 
       FIG. 3C  illustrates a side view of an exemplary pixel in a dynamic (touch) condition. An object such as finger  312  can be placed near pixel  302 . Finger  312  can be a low-impedance object at signal frequencies, and can have an AC capacitance Cfinger from the column trace  306  to the body. The body can have a self-capacitance to ground Cbody of about 200 pF, where Cbody can be much larger than Cfinger. If finger  312  blocks some electric field lines  308  between row and column electrodes (those fringing fields that exit the dielectric  310  and pass through the air above the row electrode), those electric field lines can be shunted to ground through the capacitance path inherent in the finger and the body, and as a result, the steady state signal capacitance Csig can be reduced by ΔCsig. In other words, the combined body and finger capacitance can act to reduce Csig by an amount ΔCsig (which can also be referred to herein as Csig_sense), and can act as a shunt or dynamic return path to ground, blocking some of the electric field lines as resulting in a reduced net signal capacitance. The signal capacitance at the pixel becomes Csig-ΔCsig, where ΔCsig represents the dynamic (touch) component. Note that Csig-ΔCsig may always be nonzero due to the inability of a finger, palm or other object to block all electric fields, especially those electric fields that remain entirely within the dielectric material. In addition, it should be understood that as finger  312  is pushed harder or more completely onto the touch sensor panel, finger  312  can tend to flatten, blocking more and more of the electric fields lines  308 , and thus ΔCsig can be variable and representative of how completely finger  312  is pushing down on the panel (i.e., a range from “no-touch” to “full-touch”). 
       FIG. 4A  illustrates an exemplary touch sensor circuit corresponding to a self-capacitance touch pixel electrode and sensing circuit according to examples of the disclosure. Touch sensor circuit  409  can have a touch pixel electrode  402  with an inherent self-capacitance to ground associated with it, and also an additional self-capacitance to ground that can be formed when an object, such as finger  412 , is in proximity to or touching the touch pixel electrode  402 . The total self-capacitance to ground of touch pixel electrode  402  can be illustrated as capacitance  404 . Touch pixel electrode  402  can be coupled to sensing circuit  414 . Sensing circuit  414  can include an operational amplifier  408 , feedback resistor  416 , feedback capacitor  410  and an input voltage source  406 , although other configurations can be employed. For example, feedback resistor  416  can be replaced by a switch capacitor resistor. Touch pixel electrode  402  can be coupled to the inverting input of operational amplifier  408 . An AC voltage source  406  can be coupled to the non-inverting input of operational amplifier  408 . Touch sensor circuit  409  can be configured to sense changes in the total self-capacitance  404  of touch pixel electrode  402  induced by finger  412  either touching or in proximity to the touch sensor panel. Output  420  can be used by a processor to determine a presence of a proximity or touch event, or the output can be inputted into a discreet logic network to determine the presence of a touch or proximity event. 
       FIG. 4B  illustrates an exemplary self-capacitance touch sensor panel according to examples of the disclosure. Touch sensor panel  430  can include a plurality of touch pixel electrodes  402  coupled to sense channels in touch controller  406 , can be driven by stimulation signals from the sense channels through drive/sense interface  425 , and can be sensed by the sense channels through the drive/sense interface  425  as well. After touch controller  406  has determined an amount of touch detected at each touch pixel electrode  402 , the pattern of touch pixels in the touch screen panel at which touch occurred can be thought of as an “image” of touch (e.g., a pattern of fingers touching the touch screen). 
       FIG. 5  illustrates an exemplary configuration of a device coupled to a charger according to examples of the disclosure. Device  500  can be a portable electronic device that can include data processing, storage and display components that are integrated (i.e., embedded or otherwise made an operating part of the device) into the device and are powered by a battery  534 . The term “battery” is used generically here to refer to a rechargeable power system such as a fuel cell system that can be replenished by being coupled to an external power source or charger such as power adapter  550 . Battery  534  can be, for example, a Lithium ion battery. In some examples, the charger can be any source that provides power to the battery and can include charging through a wired or wireless connection. 
     Device  500  can include a power supply circuit  536 . Power supply circuit  536  can be coupled to various components of device  500  such as host processor  528 . Power supply circuit  536  can draw current from battery  534  and can supply the current to the rest of the components of device  500 . Power supply circuit  536  can also include a switching voltage regulator and/or a dc-dc converter, to maintain a regulated power supply voltage needed by the components. 
     Power supply circuit  536  can also include a power management unit to perform various power management functions. The power management functions can include detecting whether or not device  500  is coupled to power adapter  550 , monitoring available energy in battery  534 , and notifying host processor  528  of a low battery state. The power supply circuit  536  can detect whether or not device  500  is coupled to power adapter  550  by monitoring an input voltage level, for example. If the input voltage level is above a predetermined value, the power supply circuit  536  can determine that device  500  is coupled to power adapter  550 . If the input voltage is level is below the predetermined value, the power supply circuit  536  can determine that device  500  is not coupled to power adapter  550 . In response to receiving the low notification, host processor  528  can perform any number of functions including switching to a low power consumption mode. 
     Power adapter  550  can introduce or add noise during the process of charging battery  534  or while power adapter  550  is coupled to device  500 . A touch pixel, such as touch pixel  302  of  FIG. 3A  and touch pixel electrode  402  of  FIG. 4A , stimulated by a noise source, such as power adapter  550 , can adversely affect one or more components, such as the touch sensor panel. In some examples, power adapter  550  can inform power supply circuit  536  that a charge is being supplied instead of, or in addition to, the power supply circuit  536  detecting that the device  500  is coupled to power adapter  550 . For example, the charger can send a predetermined message to device  500 . If the power adapter  550  is coupled to device  500 , the predetermined message can be received by power supply circuit  536  and can serve as an indication of a charge being supplied. 
     In some examples, the stimulating noise source can cause false touch readings for untouched locations on the touch sensor panel. This can occur when the noise source stimulates a sensor from the sensor location currently being stimulated by a drive line at an untouched location in the touch sensor panel. Since different sensors can share the same sense line in certain touch sensor panel configurations, a false touch event can be indicated when a panel-stimulated signal generated on a sense line by a sensing element at a non-touched sensor is combined with a noise-stimulated signal generated on the same sense line by a sensing element at a different touch sensor. Since a touch event is indicated at the intersection between the panel-stimulated drive line and the touch-indicating sense line, the panel can incorrectly identify a touch at the untouched location. In some examples, the stimulating noise source can cause saturation of analog touch detection circuitry, thereby preventing the circuitry from recognizing a touch event. 
     In some examples, the touch location can be calculated using an algorithm that utilizes detected capacitance values from multiple touch pixels. The algorithm can return a touch location with a resolution higher than the number of pixels. The stimulating noise source can lead to erroneous touch locations. 
     To prevent adverse effects to the touch sensor panel while the device is charging, the touch controller or processor can time multiplex touch scan periods and inductive charging periods.  FIG. 6A  illustrates an exemplary touch scan while a device is not charging. Touch sensing can operate at a suitable frequency with a touch scan time period T. For example, the frequency can be 60 Hz and the touch scan time period T can be less than 16.66 milliseconds. Every touch scan time period T, the touch controller can perform a scan for an object touching or hovering over the touch surface when the touch scan signal shown in  FIG. 6A  is high. If, however, the device is connected to an inductive charger, the inductive waveform from the inductive charger can interfere with the touch scan. The noise from the inductive waveform can corrupt the touch signal, as shown in  FIG. 6B . 
     One way to prevent corrupt touch signals due to noise from the charger or inductive charger can be to perform a touch scan during periods when the charger is not charging, as shown in  FIG. 6C . The charger can duty cycle its charging periods, and the touch controller can perform a scan during “clean,” charge-free periods. While this method could lead to noise-free touch scans, the touch controller may not know when the clean, charge-free periods will occur. 
     Another way to prevent corrupt touch signals can be to have the host processor tell the inductive charger to turn off its inductive power during touch scans. One issue with having the host processor communicate to the charger can be the processing load required to enable and execute such communication. 
       FIG. 7A  illustrates an exemplary touch scan and  FIG. 7B  illustrates a process for time multiplexed touch detection and power charging according to examples of the disclosure. The touch controller can perform multiple scans during a touch scan period or an inductive charging period T (step  752  of process  750 ). Some of the touch scans can be performed during a noise period  730  (i.e., a period with inductive charging), and some of the touch scans can be performed during a noise-free period  732  (i.e., a period with no inductive charging). In some examples, the duty cycle of the inductive charging can be less than the duty cycle of the touch scan. 
     The touch controller (or processor) can determine whether each scan is includes noise or is noise-free (step  754 ). The touch controller can discard or ignore the touch scans performed during a noise period (step  756 ), and can keep the touch scans performed during a noise-free period (step  758 ). For example, touch controller can discard “bad” touch scans  722  and  724  during noise period  730 , while keeping “good” touch scans  726  and  728  during noise-free period  732 . In some examples, the touch controller can keep one touch scan performed during a noise-free period  732  (such as touch scan  726 ) and can discard any remaining touch scans performed during the same noise-free period  732  (such as touch scan  728 ). In some examples, touch controller can average a plurality of touch scans (such as touch scans  726  and  728 ) during a noise-free period  732  (step  760 ) by averaging the touch values of individual touch pixels in the plurality of scans. 
     In some examples, the scan period  734  can be decreased (i.e., less than a scan period when the device is not connected to a charger) and the number of touch scans within the touch scan period T can be increased (i.e., greater than the number of touch scans when the device battery is not connected to a power adapter or inductive charger) when the device is coupled to the power adapter or the inductive charger. For example, the number of touch scans within the touch scan time T of  FIG. 7A  is four. If the touch controller determines that the number of good scans (those entirely in noise-free period  732 ) is less than a predetermined number, then the touch controller can increase the number of touch scans within the touch scan period T. 
     In some examples, the scan period  734  and number of touch scans within the touch scan period T can be based on the total charge time (i.e., time duration or percentage charge required to reach 100% battery life) and power consumption. For example, if the battery has a 10% battery life (i.e., 90% charge required to reach 100% battery life), the power adapter or inductive charger can increase the duty cycle for inductive charging (i.e., noise-free period  732  is decreased) in order to reduce the time required to reach 100% battery life. As a result, the number of touch scans may need to be increased in order to achieve good touch scans during the noise-free period  732 . In some examples, the number of touch scans within the touch scan period T can lead to a significant amount of power consumption, causing an increased time required to reach 100% battery life. If the device determines that this increased time is greater than a predetermined number, then the number of touch scans can be reduced. 
     Determining whether a touch scan is a bad touch scan can include performing a touch scan across the array of touch pixels and making a determination based on the scan profile.  FIG. 8A  illustrates a touch scan profile of a noise-free touch image on a touch sensor panel according to examples of the disclosure. Each touch pixel can have a measured change in capacitance value, where the measurements closer to the center of an object touching or hovering over the touch screen surface can be greater than measurements further from the center (i.e., the change in capacitance value can be higher at locations where the object is blocking electric field lines). 
     The profile of a noise-free touch image can be exhibit a profile as shown in  FIG. 8A  with a curve  805 , such as a Gaussian curve, for example. Curve  805  can have a local maximum  807 , which can represent the center of the object, for example. Curve  805  can also have tail ends  809  on either side of local maximum  807 . The profile can be quantified using different metrics such as the instantaneous slope of tail ends  809 , a full-width half-maximum  812 , and a monotonicity of curve  805 . In some examples, the profile can characteristics indicative of a plurality of touches such as a two-finger touch. The two-finger touch profile can resemble two curves such as curve  805  located side-by-side. 
       FIG. 8B  illustrates a touch scan profile of a touch image affected by noise according to examples of the disclosure. The touch controller can discard touch scans that have a profile such as the profile shown by curve  825 . Curve  825  may not exhibit certain characteristics such as the instantaneous slope of tail ends, full-width half-maximums, and monotonicity values that curve  805  exhibits. Curve  825  can represent a no touch, touch, or false touch measured during the noise period. 
     In some examples, the profile of the touch image can be stored in a memory. The touch controller can compare a profile of a touch image with a history of profiles, and a determination whether a touch is corrupted by noise can be made based on the comparison. For example, the curve of an untouched surface can be flat or can exhibit characteristics of a noisy signal such as random fluctuations. In some examples, the history of profiles can include a profile with a predetermined curve. In some examples, the touch controller can keep track of the number of bad scans or percentage of bad scans relative to the number of total scans. Based on the number of bad scans or percentage of bad scans to the total scans, the touch controller can dynamically change the scan period (such as scan period  734 ), the touch scan frequency, the number of touch scans within a touch scan time, and/or the inductive charging frequency. 
     In some examples, the determination of a bad touch scan can be based on a single touch point along the array or a subset of touch pixels. In some examples, determination of a bad touch scan can be based on all of the touch points. In some examples, touch points located substantially near the edges of the touch screen or touch sensor panel can be discarded. 
     In some examples, the touch controller can perform multiple scans on a single pixel. Determination of a bad or good touch scan can be time based. The capacitance value from the single pixel can be compared to a capacitance value from the same pixel during a previous time. If the capacitance value at any given time is not substantially the same as the mean or median value, then the touch scan can be a bad touch scan. 
     By time multiplexing the touch scan periods and inductive charging periods (i.e., touch charge mode), the touch controller can receive touch images that are not corrupted by noise. However, time multiplexing can also lead to a longer charge time (i.e., the amount of time to reach 100% battery life) than when not time multiplexing (i.e., charging the entire time). As such, in some examples, the host processor can send a notification to the power supply circuit when a touch is no longer detected. In response to the notification, the power supply circuit can notify the charger, and the charger can switch to charging the entire time or a substantial amount of the entire time (i.e., a normal charge mode). 
     In some examples, the charger can charge using a normal charge mode. When the touch sensor panel detects a first touch, the first touch scan can be during a noise period. Instead of determining a location and/or discarding the bad touch scan, the touch controller can send a notification to the charger. In response to receiving the notification, the charger can switch to the touch charge mode. In some examples, the device can include a button, and a force on the button can generate the notification. In some examples, detection of the first touch and/or force on the button can cause the device to exit a sleep state. In some examples, the charger or dock can communicate with the device during the one or more noise periods (such as noise period  730  of  FIG. 7A ). Communication can include transferring data such as a notification of the charger coupled to the device through one or more communication lines. 
     In some examples, the host processor or touch controller can determine whether a touch scan is a good touch scan or a bad touch scan. In some examples, the processing need not be performed on the device itself.  FIG. 9  illustrates an exemplary configuration in which a device is connected to a host according to examples of the disclosure. Host  910  can be any device external to device  900  including, but not limited to, any of the systems illustrated in  FIGS. 1A-1C  or a server, for example. Device  900  can be connected to host  910  through communications link  920 . Communications link  920  can be any connection including, but not limited to, a wireless connection and a wired connection. Exemplary wireless connections can be Wi-Fi, Bluetooth, Wireless Direct, and Infrared. Exemplary wired connections can be Universal Serial Bus (USB), FireWire, Thunderbolt, or any connection requiring a physical cable. 
     In operation, instead of processing the information on device  900  itself, device  900  can send raw data  930  over communications link  920  to host  910 . Host  910  can receive raw data  930 , and host  910  can process the information. Processing the information can include determining whether a touch scan is a good touch scan or a bad touch scan or dynamically changing the scan period, the touch scan frequency, the number of touch scans within a touch scan time, and/or the inductive charging frequency. In some examples, host  910  can process false touches, and can discard false touches without generating a notification to device  900 . Host  910  can also include storage or memory for tracking good touch scans and bad touch scans. Host  910  can send the processed result  940  or related information back to device  900 . Based on the processed result  940 , device  900  can notify the user or adjust its operation accordingly. By offloading the processing and/or storage of the information, device  900  can conserve space and power enabling device  900  to remain small and portable, as space that could otherwise be required for processing logic can be freed up on the device. 
     In some examples, a method of scanning a touch sensor panel is disclosed. The method may comprise: acquiring data from a plurality of touch sensors; determining whether the data includes noise, the noise generated by a charger; and discarding the data when the data includes the noise. Additionally or alternatively to one or more examples disclosed above, in other examples, the determination includes: determining a curve of a touch profile from the acquired data; determining a shape of the curve; and comparing the shape of the curve to the shape of a historical touch profile. Additionally or alternatively to one or more examples disclosed above, in other examples, the curve is a Gaussian curve. Additionally or alternatively to one or more examples disclosed above, in other examples, the determination further includes determining a slope of the curve and using the slope in the comparison. Additionally or alternatively to one or more examples disclosed above, in other examples, the determination includes determining a full-width half-maximum of the curve. Additionally or alternatively to one or more examples disclosed above, in other examples, the method further comprises determining a number of scans including the noise and a total number of scans during a scan period. Additionally or alternatively to one or more examples disclosed above, in other examples, the method further comprises dynamically changing at least one of a scan period, a scan frequency, and a number of touch scans within the scan period. Additionally or alternatively to one or more examples disclosed above, in other examples, the method further comprises generating an indication of a first touch. Additionally or alternatively to one or more examples disclosed above, in other examples, the acquiring data includes acquiring data for a plurality of touch scans, and wherein the determining whether the data includes noise includes a time based method. 
     In some examples, a method of a first device communicating with a second device is disclosed. The method may comprise: sending, to a second device, one or more touch values from sense circuitry; and receiving, from the second device, at least one of a noise-free touch image, scan period, and a number of touch scans within a scan period. 
     In some examples, a touch sensor panel is disclosed. The touch sensor panel may comprise: sensing circuit configured to acquire data from a plurality of touch sensors; logic configured to determine whether the data includes noise and discard the data when the data includes noise, wherein the noise is generated by a charger. Additionally or alternatively to one or more examples disclosed above, in other examples, the logic is further configured to determine a curve of a touch profile from the acquired data, determine a shape of the curve, and compare the shape of the curve to the shape of a historical touch profile. Additionally or alternatively to one or more examples disclosed above, in other examples, the historical touch profile includes a predetermined curve. Additionally or alternatively to one or more examples disclosed above, in other examples, the logic is further configured to determine a slope of the curve and using the slope for the comparison. Additionally or alternatively to one or more examples disclosed above, in other examples, the logic is further configured to determine a full-width half-maximum of the curve. Additionally or alternatively to one or more examples disclosed above, in other examples, the logic is further configured to determine a number of scans including the noise and a total number of scans during a scan period. Additionally or alternatively to one or more examples disclosed above, in other examples, the logic is further configured to dynamically change at least one of a scan period, a scan frequency, and a number of touch scans within the scan period. Additionally or alternatively to one or more examples disclosed above, in other examples, the logic is further configured to generate an indication of a first touch. 
     In some examples, a charger is disclosed. The charger may comprise logic configured for dynamically changing a duty cycle of a charging period. Additionally or alternatively to one or more examples disclosed above, in other examples, the duty cycle of the charging period is less than a duty cycle of a scan period of a touch sensor panel. 
     While various examples have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. Although examples have been fully described with reference to the accompanying drawings, the various diagrams may depict an example architecture or other configuration for this disclosure, which is done to aid in the understanding of the features and functionality that can be included in the disclosure. The disclosure is not restricted to the illustrated exemplary architectures or configurations, but can be implemented using a variety of alternative architectures and configurations. Additionally, although the disclosure is described above in terms of various examples and implementations, it should be understood that the various features and functionality described in one or more of the examples are not limited in their applicability to the particular example with which they are described. They instead can be applied alone or in some combination, to one or more of the other examples of the disclosure, whether or not such examples are described, and whether or not such features are presented as being part of a described example. Thus, the breadth and scope of the present disclosure should not be limited by any of the above-described examples.

Metadata:
Filing Date: 20140623
Publication Date: 20171107
Grant Date: 20171107
Priority Date: 20140623
Inventors: SAUER CHRISTIAN M.
MOYER TODD K.
PARNELL ROBERT S.
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J7/00711", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/00711", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0418", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/0093", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0418", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04166", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04166", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0418", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 54869624