Classifications

• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
  • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
  • G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
  • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
  • G06F3/0416—Control or interface arrangements specially adapted for digitisers
  • G06F3/04166—Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
  • H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
  • H03K17/96—Touch switches
  • H03K17/962—Capacitive touch switches
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K2217/00—Indexing scheme related to electronic switching or gating, i.e. not by contact-making or -breaking covered by H03K17/00
  • H03K2217/94—Indexing scheme related to electronic switching or gating, i.e. not by contact-making or -breaking covered by H03K17/00 characterised by the way in which the control signal is generated
  • H03K2217/9401—Calibration techniques

Definitions

• Embodiments relate to capacitive touch sensor devices, and more particularly to methods and apparatus for configuring capacitive touch sensor devices.
• Capacitive touch sensor devices have been incorporated into a variety of consumer electronics, including cellular telephones, computers, portable entertainment devices, appliances, and touch screens, to name a few.
• a capacitive touch sensor device includes one or more sensors (or “electrodes"), a charging circuit, and a touch detection circuit.
• Each sensor may be associated with a possible user input.
• a cellular telephone may include an array of at least twelve sensors, with ten of the sensors being associated with each of the numbers from 0 to 9, an eleventh sensor being associated with a "SEND" key, and a twelfth sensor being associated with an "END" key.
• a typical sensor includes a dielectric touch plate (e.g., a glass plate) and an electrode, which function as a dielectric and an electrode of a capacitor, respectively.
• a dielectric touch plate e.g., a glass plate
• an electrode which function as a dielectric and an electrode of a capacitor, respectively.
• the capacitive touch sensor device periodically and frequently measures the potential of the electrode in order to determine whether or not a touch has occurred.
• the charging circuit Prior to measuring the potential, charges the electrode by providing the electrode with a pre-determined current for a predetermined time. At the culmination of the charging process, the touch determination circuit measures the voltage between the electrode and ground (or some other fixed potential).
• the touch determination circuit may indicate that a touch has been sensed.
• the charging and measurement procedures continue to be repeated, and when the measured voltage later rises toward the baseline value by a sufficient amount (e.g., above a release detection threshold), the touch determination circuit may then indicate that a release has been sensed.
• the theoretical range of charges that can be applied to the electrode is constrained to correspond to measurable voltages between zero volts (or ground) and the supply voltage to the device.
• accurate charging and measurement typically can be obtained only for voltages that fall within a central range of the theoretical range.
• FIG. 1 illustrates a simplified block diagram of a portion of an electronic system within which a capacitive touch sensor system is incorporated, according to an example embodiment
• FIG. 2 illustrates a simplified block diagram of a capacitive touch sensor, according to an example embodiment
• FIG. 3 is a chart illustrating an example of an electrode charging/discharging profile for a plurality of charging and measurement cycles for a selected electrode, according to an embodiment
• FIG. 4 is a chart illustrating example electrode voltage measurements plotted in conjunction with a baseline and touch/release detection thresholds, according to an example embodiment
• FIG. 5 is a flowchart of a method for performing touch/release detection and configuring a capacitive touch sensor, according to an example embodiment
• FIG. 6 is a flowchart of a method for configuring or reconfiguring the charging parameters for an electrode, according to an example embodiment.
• FIG. 7 is a flowchart of a method for configuring or reconfiguring the charging parameters for an electrode, according to another example embodiment.
• Capacitive touch sensor devices are needed, which may reliably achieve accurate touch detection in the face of significant capacitance changes due to external factors. Further needed are capacitive touch sensor devices that allow system designers to set charging parameters for increased sensitivity, if they so choose, while still achieving high reliability. Further needed are methods and apparatus for configuring capacitive touch sensor devices, which may enable system manufacturers to have higher device yields, when compared with device yields of conventional devices.
• Embodiments described herein include capacitive touch sensor devices and methods for configuring capacitive touch sensor devices.
• Embodiments include capacitive touch sensor devices that may reliably achieve accurate touch detection in the face of significant capacitance changes due to external factors.
• Embodiments also may allow system designers to set charging parameters for increased sensitivity, if they so choose, while still achieving high reliability.
• embodiments may enable system manufacturers to have higher device yields, when compared with device yields of conventional devices. More details of various embodiments will now be described in conjunction with FIGs 1-7.
• FIG. 1 illustrates a simplified block diagram of a portion of an electronic system
• the system 100 within which a capacitive touch sensor system is incorporated, according to an example embodiment.
• the portion of the system 100 may be incorporated within a cellular telephone, a radio, a computer, a portable entertainment device, an appliance, a touch screen, or any of various other types of electronic devices.
• the system 100 includes a controller 102, a capacitive touch sensor 104, and from one to N touch pad electrodes 106, 107, 108, where N is an integer (e.g., an integer in a range from 1 to hundreds).
• Each touch pad electrode 106-108 is arranged in physical proximity to a dielectric touch plate (or a portion thereof). Each electrode 106-108 and its associated dielectric touch plate function as one electrode and a dielectric of a capacitor, respectively. As with a
• the capacitive touch sensor 104 can determine whether the capacitance associated with an electrode 106-108 has changed sufficiently to indicate that a "touch event” or a "release event” has occurred.
• embodiments include methods and apparatus that perform an automatic charge configuration process, which may ensure that each electrode 106- 108 is charged to a voltage that falls within a central voltage region under a wide variety of circumstances and device variations.
• Capacitive touch sensor 104 is operatively coupled with each electrode 106-108 through charging lines 120, 121 , 122 and measurement lines 130, 131 , 132.
• charging lines 120- 122 and measurement lines 130-132 are shown to be distinct lines in FIG. 1 , it is to be understood that the charging and measurement processes may be performed for an electrode over a single line (e.g., charging line 120 and measurement line 130 are the same line). In other words, the charging and measurement processes may be performed for an electrode using two pins or a single pin of capacitive touch sensor 104, according to various embodiments.
• capacitive touch sensor 104 is configured to store and dynamically maintain charge configuration information for each electrode 106-108, where the charge configuration information includes at least a baseline voltage, a charging current, and a charging interval for each electrode 106-108.
• the charge configuration information includes at least a baseline voltage, a charging current, and a charging interval for each electrode 106-108.
• capacitive touch sensor 104 supplies a current over charge line 120, where the supplied current has a magnitude equal to the stored charging current for electrode 106. The charging current is supplied for the stored charging interval for electrode 106, and then the charging process is terminated.
• Capacitive sensor 104 measures the voltage of the electrode 106 over measurement line 130, and compares the measured voltage with the stored baseline voltage for electrode 106.
• the capacitive touch sensor 104 may make a determination that electrode 106 is in a "no-touch state". Conversely, when the difference between the measured voltage and the baseline voltage exceeds the touch detection delta, the capacitive touch sensor 104 may make a determination that a touch event has occurred, and thus that electrode 106 is in a "touch state". While in the touch state, the capacitive touch sensor 104 may continue to repeat the charging and measuring process until a comparison between the measured voltage and the baseline voltage yields a difference that is less than a release detection delta. At that time, the capacitive touch sensor 104 may determine that a release event has occurred, and thus that electrode 106 is again in the no-touch state.
• Capacitive touch sensor 104 is operatively coupled with system controller 102.
• System controller 102 may include a special purpose or general purpose microprocessor, a digital signal processor, an Application Specific Integrated Circuit (ASIC), or some other type of processing component.
• System controller 102 and capacitive touch sensor 104 may include a special purpose or general purpose microprocessor, a digital signal processor, an Application Specific Integrated Circuit (ASIC), or some other type of processing component.
• System controller 102 and capacitive touch sensor 104 may include a special purpose or general purpose microprocessor, a digital signal processor, an Application Specific Integrated Circuit (ASIC), or some other type of processing component.
• ASIC Application Specific Integrated Circuit
• communication interface 1 10 may include one or more interrupt lines and one or more communication lines.
• communication interface 1 10 may include transmission means to support an I 2 C (Inter-Integrated Circuit) communication protocol, in an embodiment.
• communication interface 1 10 may include transmission means to support an SPI (Serial Peripheral Interface) protocol, a UART (Universal Asynchronous Receiver/Transmitter) protocol, or some other type of inter-processor communication protocol.
• SPI Serial Peripheral Interface
• UART Universal Asynchronous Receiver/Transmitter
• system controller 102 may provide control messages over communication interface 1 10, which are adapted to activate or deactivate capacitive touch sensor 104.
• capacitive touch sensor 104 may provide an interrupt over communication interface 1 10.
• system controller 102 may provide a request for information regarding the interrupt (e.g., a request to read a register of capacitive touch sensor 104 that describes the triggering event for the interrupt).
• Capacitive touch sensor 104 may then return data which indicates, for example, an electrode identity and an indicator of a touch event or a release event. System controller 102 may then take whatever action is appropriate, given the circumstances.
• FIG. 2 illustrates a simplified block diagram of a capacitive touch sensor 200 (e.g., capacitive touch sensor 104, FIG. 1), according to an example embodiment.
• Capacitive touch sensor 200 includes a sensor controller 202, a current source 204, a clock/timer 206, an analog-to-digital converter (ADC) 208, a multiplexer input/output (I/O) 210, and data storage 212, according to an embodiment. These components may be incorporated into a single integrated circuit, or some or all of the components may be implemented as separate devices.
• ADC analog-to-digital converter
• I/O multiplexer input/output
• Sensor controller 202 is configured to communicate with an external controller
• sensor controller 202 may initiate the process of monitoring one or more external electrodes (e.g., electrodes 106-108, FIG. 1) to determine whether voltages present on the electrodes exhibit properties indicating a no-touch state, a touch state, a touch event or a release event.
• sensor controller 202 may store, via lines 258, information describing the event in data storage 212, and may send an interrupt over an interrupt line 260.
• the information describing the event may include, for example, an electrode identity and the type of event (e.g., touch or release). Alternatively, the information may include an electrode identity and the electrode's current state (e.g., touch state or no-touch state).
• sensor controller 202 may store an indication of the newly entered state in data storage 212. For example, sensor controller 202 may store an indication that the electrode is in a touch state when a touch event occurs, and sensor controller 202 may store an indication that the electrode is in a no-touch state when a release event occurs.
• sensor controller 202 may retrieve the information from data storage 212, and may send a response over a communication line 240 that includes the event description.
• Sensor controller 202 also may receive a control message over communication line 240, which indicates that sensor controller 202 should discontinue electrode monitoring (e.g., when the device is powering down), and sensor controller 202 may discontinue electrode monitoring accordingly.
• Data storage 212 may include one or more registers or other volatile storage means adapted to store touch and release event information and electrode-specific parameters, which will be discussed in more detail below.
• data storage 212 may include one or more non-volatile storage means adapted to store sensor initialization information.
• sensor initialization information may include, for each electrode monitored by capacitive touch sensor 200, default charging parameters.
• the default charging parameters may include, for example, a default charging current, a default charging interval, and a default baseline value associated with a no-touch condition.
• data storage 212 may include a touch detection delta value and a release detection delta value.
• data storage 212 may include a default touch detection threshold (e.g., the default baseline value minus a touch detection delta) and a default release detection threshold (e.g., the default baseline value minus a release detection delta).
• a default touch detection threshold e.g., the default baseline value minus a touch detection delta
• a default release detection threshold e.g., the default baseline value minus a release detection delta
• sensor controller 202 may select a first electrode (e.g., electrode 106, FIG. 1) for monitoring by providing a select signal over multiplexer control line 250 to multiplexer I/O 210.
• Sensor controller 202 may retrieve the default charging parameters for the selected electrode from data storage 212, and may provide a control signal to current source 204 over control line 242, which indicates the default charging current.
• sensor controller 202 may provide a clock/timer control signal over control line 244 to clock/timer 206, which indicates the default charging interval for the selected electrode.
• Clock/timer 206 may thereafter provide an enable signal to current source 204 over control line 246, which causes current source 204 to produce a current at the default charging current on current output line 248.
• clock/timer 206 may provide a disable signal to current source 204 over control line 246, which causes current source 204 to cease providing current on current output line 248.
• the current provided on current output line 248 is provided to the selected electrode on one of charging lines 220, 221 , 222.
• FIG. 3 is a chart illustrating an example of an electrode charging/discharging profile 300 for a plurality of charging and measurement cycles for a selected electrode, according to an embodiment.
• Current e.g., current at the default or stored charging current
• the electrode e.g., by current source 204, FIG. 2
• voltage segment 302 shows an electrode voltage increasing linearly from zero volts (e.g., for a properly grounded electrode) to a target voltage 304 during a charging interval 306.
• the target voltage 304 desirably falls between a lower voltage threshold 308 and an upper voltage threshold 310, which together bound a target voltage range 312 within the theoretical voltage range.
• the target voltage range 312 may correspond with a central range of the theoretical operating range of the device, where the theoretical operating range may be from zero volts to the supply voltage, V DD , for example. More particularly, the lower voltage threshold 308 may correspond to a voltage below which accurate measurement may not be reliably achieved, and the upper voltage threshold 310 may correspond to a voltage above which accurate charging may not be reliably achieved. For example, for a device that has a supply voltage, V DD , of 1 .7 volts, reliably accurate voltage measurement may not be possible for voltages within the lower 0.7 volts of the range, and reliably accurate charging may not be possible to achieve voltages within the upper 0.7 volts of the range. Accordingly, the lower voltage threshold 308 may be approximately 0.7 volts, the upper voltage threshold may be approximately 1.0 volts, and the target voltage range 312 may include approximately a 0.3 volt range between 0.7 and 1 .0 volts.
• the target voltage range 312 may be defined to be a sub-range within the central range.
• the target voltage range 312 may be defined as an upper portion of the central range (e.g., the upper 90% to 100% of the central range).
• the target voltage range 312 may be defined as a central portion of the central range (e.g., the central 45% to 55% of the central range).
• the target voltage range 312 may be established by storing (e.g., in data storage 212, FIG.
• LTRL lower target range limit
• UTRL upper target range limit
• the capacitive touch sensor may measure the voltage of the electrode.
• sensor controller 202 may perform a voltage measurement for the selected electrode by providing another control signal to multiplexer I/O 210 over multiplexer control line 250, which enables multiplexer I/O 210 to access an analog voltage signal for the selected electrode over one of measurement lines 230, 231 , 232.
• charging lines 220-222 and measurement lines 230-232 are shown to be distinct lines in FIG. 2, it is to be understood that the charging and measurement processes may be performed for an electrode over a single line (e.g., charging line 220 and measurement line 230 may be the same line).
• Multiplexer I/O 210 provides the analog voltage signal to ADC 208 over analog voltage line 252.
• ADC 208 converts the received analog voltage signal to a digital value, which may be represented as an ADC count, according to an embodiment.
• ADC 208 samples the analog voltage signal in order to produce a plurality of digital values.
• ADC 208 then provides the sampled, digital values to sensor controller 256 over digital voltage line 256.
• the electrode may then be discharged to zero volts during a discharge interval 316, and the process may be repeated one or more times in order to obtain one or more additional voltage measurements for the same selected electrode. More particularly, sensor controller 202 may cause the charging and voltage measurement processes to be repeated one or more times for the selected electrode, and may then evaluate the measured voltages to determine, for example, whether a touch event or a release event has occurred.
• determination of whether a touch event or a release event has occurred may include using a plurality of voltage measurements to determine a "short-term” electrode voltage value ("STEW"), and using a plurality of STEWs to determine a "long-term” electrode voltage value (“LTEW”). The LTEW may then be evaluated to determine how the value compares with touch detection and touch release thresholds.
• STEM short-term electrode voltage value
• LTEW long-term electrode voltage value
• a measured “electrode voltage” or “electrode voltage value” may generically refer to a single measured electrode voltage value or a mathematically derived electrode voltage value based on a plurality of electrode voltage value measurements (e.g., an STEW, an LTEW, or another electrode voltage value that is derived from a plurality of measurements).
• Sensor controller 202 may then select another electrode (e.g., electrode 107, FIG.
• One or more of the initial charging and measuring iterations may use default values (e.g., a default charging current and default charging interval), as described above.
• the default values may be stored in data storage 212 in the factory during manufacture of the capacitive touch sensor 200, or may be initialized by a system designer who is incorporating the capacitive touch sensor 200 into a system (e.g., electronic system 100, FIG. 1).
• sensor controller 202 automatically may reconfigure the system by updating (e.g., determining and storing in data storage 212) different charging parameters for one or more of the electrodes during operation in the field. This may include updating the charging current and/or the charging interval for one or more of the electrodes.
• sensor controller 202 may automatically update, for each electrode, the baseline value associated with a no-touch condition, the touch detection threshold (and/or the touch detection delta value), and the release detection threshold (and/or the release detection delta value). Methods and apparatus for configuring and automatically reconfiguring the system and updating the various parameters will be discussed in more detail in conjunction with FIGs 5-7.
• capacitive touch sensor 200 is adapted to perform automatic configuration and/or reconfiguration processes, according to an embodiment.
• the automatic configuration process includes initially determining and storing a baseline value, a charging current, and a charging interval for each electrode (referred to herein as a "stored baseline value,” a “stored charging current,” and a “stored charging interval,” respectively).
• the automatic reconfiguration process includes updating (e.g., determining and storing) the stored baseline value, the stored charging current, and the stored charging interval for each electrode.
• An automatic configuration process or an automatic reconfiguration process may be referred to simply as a "configuration process," herein.
• the automatic configuration process may be performed in conjunction with the charging and measurement procedures performed for each electrode.
• the capacitive touch sensor 200 may evaluate measured voltages to determine whether a touch event or a release event has occurred.
• determining whether a touch event has occurred includes determining whether the measured voltage is above or below a touch detection threshold. Conversely, when the electrode is in a touch state, determining whether a release event has occurred includes determining whether the measured voltage is above or below a release detection threshold.
• FIG. 4 is provided in conjunction with describing the baseline value, the touch detection threshold, and the release detection threshold. More particularly, FIG. 4 is a chart 400 illustrating example voltage measurements 420, 421 , 422 plotted in conjunction with a baseline 402 and touch/release detection thresholds 406, 412 for a single electrode, according to an example embodiment. Although only three discrete electrode voltage measurements 420-422 are indicated in FIG. 4, the voltage measurement signal 404 represents a plurality of measurement points, which are shown to be connected together as a continuous voltage measurement signal 404 for clarity of description. Similarly, although the baseline 402 is illustrated as a continuous signal for clarity of description, the baseline actually may be represented in the system by the stored baseline value.
• each voltage measurement 420-422 may represent the result of a single measurement for a single charging and measurement cycle for the electrode, or each voltage measurement 420-422 may represent a plurality of measurements for a plurality of charging and measurement cycles for the electrode (e.g., an STEW or an LTEW). Either way, the voltage measurements 420-422 may be different from measurement-to- measurement, as is depicted in FIG. 4. [0036] Beginning from the left side of chart 400, a plurality of voltage measurements
• the touch detection threshold 406 is equal to the stored baseline value minus a touch detection delta 430.
• the touch detection delta 430 is a fixed value, although the touch detection delta 430 may be an adjustable value in another embodiment.
• FIG. 4 illustrates that voltage measurement 420 is above the touch detection threshold 406, and accordingly a comparison of voltage measurement 420 with the touch detection threshold 406 will indicate that the electrode is in the no-touch state.
• the baseline 402 may be dynamically adjusted while the electrode is in the no-touch state, as will be discussed in more detail later. Dynamic adjustment of baseline 402 is shown in FIG. 4 by the increasing and decreasing nature of baseline 402 during time interval 410. As baseline 402 is dynamically adjusted, the touch detection threshold 406 and the touch release threshold 412 also are dynamically adjusted, as depicted in FIG. 4.
• the voltage measurement signal 404 drops below the touch detection threshold 406 at time 408. Accordingly, a comparison of voltage measurement 421 with the touch detection threshold 406 will indicate that the electrode is now in the touch state.
• the system may generate an interrupt (e.g., on an interrupt line 260, FIG. 2) when a transition from a no-touch state to a touch state is detected.
• the electrode may be considered to remain in a touch state when voltage measurements for the electrode have values that are below a touch release threshold 412.
• the touch release threshold 412 is equal to the stored baseline value minus a touch release delta 432.
• the electrode remains in the touch state.
• the voltage measurement signal 404 rises above the release detection threshold 412 at time 414. Accordingly, a comparison of voltage measurement 422 with the release detection threshold 412 will indicate that the electrode is once again in the no-touch state.
• the electrode may be considered to remain in the no-touch state when voltage measurements for the electrode have values that are above the touch detection threshold 406.
• the touch release threshold 412 is at a different voltage from the touch detection threshold 406, which provides hysteresis in the system. More particularly, the touch release threshold 412 is at a higher voltage than the touch detection threshold 406. In an alternate embodiment, the touch release threshold 412 may be at a lower voltage than the touch detection threshold 406. In yet another alternate embodiment, the touch release threshold 412 and the touch detection threshold 406 may be equal, in which case the system may maintain only one threshold for comparison purposes. These various embodiments are intended to be included within the scope of the inventive subject matter.
• FIG. 5 is a flowchart of a method for performing touch/release detection and configuring a capacitive touch sensor, according to an example embodiment.
• the entire method may be performed by a capacitive touch sensor (e.g., capacitive touch sensor 200, FIG. 2) without assistance from any external processing entity (e.g., system controller 102, FIG. 1).
• any external processing entity e.g., system controller 102, FIG. 1.
• portions of the method may be performed by an external processing entity.
• the method may begin, in block 500, by performing an electrode configuration process in which initial charging parameters (e.g., an initial charging current, an initial charging interval, and an initial baseline value associated with a no-touch condition) are determined (e.g., by the capacitive touch sensor) and stored in the system (e.g., in data storage 212, FIG. 2) for each electrode (e.g., electrodes 106-108, FIG. 1).
• the electrode configuration process may be a system feature that is capable of being enabled or disabled.
• block 500 When disabled, block 500 may be bypassed, and the method may instead be initiated using default charging parameters (e.g., a default charging current, a default charging interval, and a default baseline value associated with a no-touch condition) that have been pre-stored in the system (e.g., in data storage 212, FIG. 2 during factory calibration).
• default charging parameters e.g., a default charging current, a default charging interval, and a default baseline value associated with a no-touch condition
• the initial configuration process i.e., block 500
• the initial configuration process i.e., block 500
• FIGs 6 and 7, later Various embodiments for performing a configuration process will be discussed in more detail in conjunction with FIGs 6 and 7, later.
• the capacitive touch sensor may enter an electrode monitoring state, within which the capacitive touch sensor repeatedly determines whether touch or release events are occurring for the system's electrodes.
• Blocks 502-528 are associated with the electrode monitoring state. Although it may take several iterations of blocks 502-528 for the capacitive touch sensor to reach steady state operation, the below description assumes that a sufficient number of electrode voltage measurements have been performed to establish the capacitive touch sensor into steady state operation.
• an electrode e.g., one of electrodes
• selection of an electrode may include a controller (e.g., sensor controller 202, FIG. 2) providing a select signal to electrode selection circuitry (e.g., providing a select signal over multiplexer control line 250 to multiplexer I/O 210, FIG. 2).
• controller e.g., sensor controller 202, FIG. 2
• electrode selection circuitry e.g., providing a select signal over multiplexer control line 250 to multiplexer I/O 210, FIG. 2.
• a charging/measurement process is performed to determine a short term electrode voltage value ("STEW").
• STW short term electrode voltage value
• the charging/measurement process includes performing a pre-defined number of charging and measurement cycles, as previously depicted in FIG. 3.
• the pre-defined number of charging and measurement cycles may be from two to ten cycles, for example, although the pre-defined number of charging and measurement cycles may be as few as one or greater than ten, in other embodiments (e.g., when the pre-defined number is one, the STEW equals a single voltage measurement).
• An STEW is determined from the results of the measurement processes. For example, the STEW may be determined to be an average of the pre-defined number of measured voltages, although the STEW may be determined using other mathematical relationships, in other embodiments.
• a long term electrode voltage value is determined from a pre-defined number of STEVVs.
• the pre-defined number of STEWs may be from two to five STEWs, for example, although the pre-defined number of STEWs may be as few as one or greater than five, in other embodiments (e.g., when the pre-defined number is one, the LTEW equals a single STEW).
• the LTEVV may be determined to be an average of the pre-defined number of STEVVs, although the LTEW may be determined using other mathematical relationships, in other embodiments.
• this includes determining whether the LTEW has a value that falls within or outside of a pre-defined range of voltage values. More particularly, a determination is made whether the LTEW has a value that falls outside of a target range (e.g., target voltage range 312, FIG. 3).
• a target range e.g., target voltage range 312, FIG. 3
• the target range may be defined by a lower target range limit (“LTRL”) and an upper target range limit (“UTRL”), and may correspond to a central range of theoretical voltage values for the device, or a subset of a central range (e.g., an upper 90% to 100% of the central range for increased device sensitivity).
• determining whether the LTEW meets the criteria may include determining whether the LTEW is above or below a threshold (e.g., the lower or upper voltage thresholds 308, 310, FIG. 3).
• an automatic reconfiguration process is performed, in block 524.
• the reconfiguration process is considered to be “automatic” in that initiation of the process is based on an evaluation of a measured value (e.g., a measured voltage value such as the LTEW) by the capacitive touch sensor, and accordingly does not require a system controller (e.g., system controller 102, FIG. 1) or any other outside entity to initiate the process.
• a system controller e.g., system controller 102, FIG. 1
• the reconfiguration process may be performed during a time interval that occurs while the capacitive touch sensor is between two different detected touch states.
• the automatic reconfiguration process includes the capacitive touch sensor determining and storing new charging parameters (e.g., a new charging current, a new charging interval, or both) for the selected electrode.
• the electrode reconfiguration process may be a system feature that is capable of being enabled or disabled. When disabled, block 524 may be bypassed, and the method may instead proceed directly to block 526, which will be described later.
• Various embodiments for performing an automatic reconfiguration process will be discussed in more detail in conjunction with FIGs 6 and 7, later.
• the capacitive touch sensor may maintain (e.g., in data storage 212, FIG. 2) an indication of whether each electrode currently is in a touch state or a no-touch state.
• a further determination may be made, in block 514, whether the LTEW is above or below the touch detection threshold (e.g., touch detection threshold 406, FIG. 4).
• the LTEW when the LTEW has a value that is greater than the touch detection threshold, the LTEW may be considered to be above the touch detection threshold. Conversely, when the LTEW has a value that is less than the touch detection threshold, the LTEW may be considered to be below the touch detection threshold.
• the determination of whether the LTEW is above or below the touch detection threshold alternatively may be made by determining a difference between the LTEW and the stored baseline value (e.g., a difference between voltage measurement 421 and baseline 404, FIG. 4), and further determining whether the difference is greater than (or greater than or equal to) a touch detection delta (e.g., touch detection delta 430, FIG. 4).
• the electrode is transitioned to the touch state, in block 516.
• this may include the capacitive touch sensor storing an indication (e.g., in data storage 212, FIG. 2) that the electrode is now in the touch state.
• the capacitive touch sensor may indicate that a state transition (i.e., from the no-touch state to the touch state) has occurred.
• the capacitive touch sensor may generate an interrupt (e.g., on an interrupt line 260, FIG. 2), which indicates that the electrode has changed states.
• a system controller e.g., system controller 102, FIG. 1
• the capacitive touch sensor may return data which indicates, for example, an identity of the electrode and an indicator of a touch event. The system controller may then take whatever action is appropriate, given the
• this may include overwriting the previously stored baseline value with the LTEW.
• new touch detection and release detection thresholds may be determined and stored. This enables the baseline to be dynamically adjusted and accurately maintained in the presence of slowly-varying conditions.
• another embodiment may exclude dynamic adjustment of the baseline, this may increase a likelihood for false touch and/or release detections.
• dynamic adjustment of the baseline may be performed during time intervals when the electrode is in a no-touch state, and may be bypassed during time intervals when the electrode is in a touch state, according to an embodiment.
• a further determination may be made, in block 520, whether the LTEVV is above or below the release detection threshold (e.g., release detection threshold 412, FIG. 4). For example, when the LTEW has a value that is greater than the release detection threshold, the LTEVV may be considered to be above the release detection threshold. Conversely, when the LTEW has a value that is less than the release detection threshold, the LTEW may be considered to be below the release detection threshold.
• the release detection threshold e.g., release detection threshold 412, FIG. 4
• the determination of whether the LTEW is above or below the release detection threshold alternatively may be made by determining a difference between the LTEW and the stored baseline value, and further determining whether the difference is greater than (or greater than or equal to) a release detection delta (e.g., release detection delta 432, FIG. 4).
• a release detection delta e.g., release detection delta 432, FIG. 4
• the electrode is transitioned to the no-touch state, in block 522.
• this may include the capacitive touch sensor storing an indication (e.g., in data storage 212, FIG. 2) that the electrode is now in the no-touch state.
• the capacitive touch sensor may indicate that a state transition (i.e., from the touch state to the no-touch state) has occurred.
• the capacitive touch sensor may generate an interrupt (e.g., on an interrupt line 260, FIG. 2), which indicates that the electrode has changed states.
• a system controller e.g., system controller 102, FIG. 1
• the capacitive touch sensor may return data which indicates, for example, an identity of the electrode and an indicator of a release event.
• an idle time period e.g., from 1 to 100 milliseconds or some other time period.
• a capacitive touch sensor may automatically reconfigure an electrode based on an evaluation of an electrode voltage value (e.g., the LTEW).
• the automatic reconfiguration process may be performed substantially in hardware, according to an embodiment, or substantially in software, according to another embodiment.
• a hardware implementation may be desirable, for example, in a system that is not designed to include significant processing capabilities for cost or other reasons (e.g., a simple sensor such as a garage door opener).
• a software implementation may be desirable, for example, in a system in which significant processing capabilities are available either within the capacitive touch sensor or in a manner that is accessible to the capacitive touch sensor. Embodiments of substantially hardware implementations are discussed in conjunction with FIG. 6, and
• FIG. 6 is a flowchart of a method for configuring or reconfiguring the charging parameters for an electrode, according to an example embodiment.
• the method of FIG. 6 may be performed in conjunction with blocks 502 and/or 524 of FIG. 5.
• the method of FIG. 6 may be performed in conjunction with blocks 502 and/or 524 of FIG. 5.
• the method may begin, in block 600, by determining whether the configuration or re-configuration process is enabled or disabled. When the process is disabled, the method may end.
• the method may proceed to block 602, in which a target charging voltage is determined.
• the target charging voltage may be a voltage within a target range that either corresponds to a pre-defined central range of the theoretical operating range for the device, or within a target range that is defined in the factory or by a device designer (e.g., target voltage range 312, which is defined by lower and upper voltage thresholds 308, 310, FIG. 3).
• the target charging voltage may be selected to be anywhere within the central range or the target range.
• the target charging voltage may be selected to be in the middle of the central range or the target range, although this is not essential.
• the target charging voltage may be selected to be 0.85 volts.
• the target charging voltage may be defined in terms of an ADC count, according to an embodiment.
• an ADC count of 540 e.g., 0x87 hexadecimal
• an ADC count of 604 e.g., 0x97 hexadecimal
• the target charging voltage may be defined to correspond to an ADC count of 572 (e.g., 0x8F hexadecimal).
• the charging interval search is an iterative process in which, during each iteration, the electrode is charged with a fixed charging current and a different one of a plurality of pre-defined, selectable charging intervals.
• a set of pre-defined charging intervals may be accessible to the capacitive touch sensor (e.g., in data storage 212, FIG. 2).
• the set of pre-defined charging intervals may include from two to N values, for example.
• N seven different charging interval values
• a charging interval table alternatively may include more or fewer than seven values, and that the charging interval values may be different from those shown in Table 1.
• the charging interval search is performed as a binary search, in which a central charging interval value is selected from the table during the first searching interval (e.g., a charging interval value of 4.0 microseconds corresponding to entry number 4), and based on the results of the first iteration, a next charging interval value is selected during the second iteration, where the next selected charging interval value corresponds to an entry halfway toward the bottom or top of the table with respect to the central charging interval value (e.g., one of charging interval values 1.0 or 16.0 microseconds corresponding to entry numbers 2 and 6, respectively).
• the charging interval search process begins, in block 604, by selecting a candidate charging interval.
• a first selected candidate charging interval may correspond to a central charging interval value (e.g., a charging interval value of 4.0 microseconds corresponding to entry number 4 of Table 1 , above).
• an electrode charging process may then be performed, by applying a fixed and pre-defined current to the electrode for a duration of time that equals the candidate charging interval.
• the fixed and pre-defined current may be a current in a range of selectable currents, as will be discussed in conjunction with blocks 610, 612, 613, and 614, below.
• an electrode measurement process may be performed during which the electrode voltage is measured.
• the singular electrode voltage measurement may then be evaluated, in block 607, or the charging and measurement processes may be repeated one or more times and a mathematical determination of the electrode voltage may be determined from the multiple electrode voltage measurements (e.g., an average of the multiple measurements).
• the electrode voltage measurement is compared with the target charging voltage (as determined in block 602) to determine whether the electrode voltage measurement is higher than or lower than the target charging voltage.
• the electrode voltage measurement also may be represented as an ADC count, and the comparison performed in block 607 may include comparing the ADC count corresponding to the target charging voltage with the ADC count corresponding to the electrode voltage measurement.
• the charging interval search process may be considered to be completed, for example, when a defined number of iterations have been performed in conjunction with the binary search (e.g., three iterations in the case of a charging interval table that includes seven entries).
• the charging interval search process may be considered to be completed when the last two iterations of the searching process resulted in electrode voltage measurements on either side of the target charging voltage.
• next candidate charging interval is selected based on the comparison made in block 607. More particularly, in a table such as Table 1 above, in which candidate charging intervals are arranged in an increasing order, a lower-valued, candidate charging interval for an entry halfway toward the beginning of the table (e.g., entry number 2) is selected when the measured electrode voltage is higher than the target charging voltage, or a higher-valued, candidate charging interval for an entry halfway toward the end of the table (e.g., entry number 6) is selected when the measured electrode voltage is lower than the target charging voltage.
• a lower-valued, candidate charging interval for an entry halfway toward the beginning of the table e.g., entry number 2
• a higher-valued, candidate charging interval for an entry halfway toward the end of the table e.g., entry number 6
• next candidate charging interval may be selected as a next sequential entry in the table (e.g., if entry number 1 was selected for the first iteration, entry number 2 may be selected for the next iteration). Blocks 606, 607, and 608 may thereafter be performed for the next selected candidate charging interval.
• the final charging interval value may be one of the last two candidate charging intervals evaluated (e.g., during the last two search iterations), whichever yielded an electrode voltage measurement that was closest to the target charging voltage.
• the final charging interval value may be a value that is between the last two candidate charging intervals evaluated (e.g., halfway between or some other distance that is related to how close the last measured electrode voltage was to the target charging voltage).
• the final charging interval value may be set, for example, by storing the final charging interval value in a memory location that is accessible to the capacitive touch sensor (e.g., in data storage 212, FIG. 2).
• a charging current search is then performed in blocks 610, 612, 613, and 614.
• the charging current search is an iterative process in which, during each iteration, the electrode is charged with a fixed charging interval (e.g., the final charging interval set in block 609) and a different one of a plurality of pre-defined, selectable charging currents.
• a set of pre-defined charging currents may be accessible to the capacitive touch sensor (e.g., in data storage 212, FIG. 2).
• the set of pre-defined charging currents may include from two to M values, for example.
• a charging current table alternatively may include more or fewer than fifteen values, and that the charging current values may be different from those shown in Table 2.
• the charging current search is performed as a binary search, in which a central charging current value is selected from the table during the first searching interval (e.g., a charging current value of 16 millivolts corresponding to entry number 8), and based on the results of the first iteration, a next charging current value is selected during the second iteration, where the next selected charging current value corresponds to an entry halfway toward the bottom or top of the table with respect to the central charging current value (e.g., one of charging current values 5 or 38 microamps corresponding to entry numbers 4 and 12, respectively). Subsequent iterations continue to be performed until the binary search converges on a final value.
• a central charging current value is selected from the table during the first searching interval (e.g., a charging current value of 16 millivolts corresponding to entry number 8)
• a next charging current value is selected during the second iteration, where the next selected charging current value corresponds to an entry halfway toward the bottom or top of the table with respect to the central charging current value (e.g
• the binary search would converge to a particular charging current value (or table entry number) in four iterations.
• the below description of block 610, 612, 613 and 614 will be described in accordance with an embodiment that uses a binary search to determine a charging current value. It is to be understood, however, that other searching methods alternatively may be used, in other embodiments.
• entries in a table of pre-defined charging current values may be selected linearly (e.g., starting from entry number 1), or may be selected in some other sequence.
• the charging current search process begins, in block 610, by selecting a candidate charging current.
• a first selected candidate charging current may correspond to a central charging current value (e.g., a charging current value of 16 millivolts corresponding to entry number 8 of Table 2, above).
• an electrode charging process may then be performed, by applying the candidate charging current to the electrode for a fixed duration of time (e.g., the final charging interval set in block 609).
• an electrode measurement process may be performed during which the electrode voltage is measured.
• the singular electrode voltage measurement may then be evaluated, in block 613, or the charging and measurement processes may be repeated one or more times and a mathematical determination of the electrode voltage may be determined from the multiple electrode voltage measurements (e.g., an average of the multiple measurements). Either way, in block 613, the electrode voltage measurement is compared with the target charging voltage (as determined in block 602) to determine whether the electrode voltage measurement is higher than or lower than the target charging voltage.
• the charging current search process may be considered to be completed, for example, when a defined number of iterations have been performed in conjunction with the binary search (e.g., four iterations in the case of a charging current table that includes fifteen entries). In an alternate embodiment (e.g., when a linear search through the charging current table is performed), the charging current search process may be considered to be completed when the last two iterations of the searching process resulted in electrode voltage measurements on either side of the target charging voltage. [0070] When it is determined that the charging current search process is not completed, then a next searching iteration is initiated by again selecting a candidate charging current in block 610.
• the next candidate charging current is selected based on the comparison made in block 613. More particularly, in a table such as Table 2 above, in which candidate charging currents are arranged in an increasing order, a lower-valued, candidate charging current for an entry halfway toward the beginning of the table (e.g., entry number 4) is selected when the measured electrode voltage is higher than the target charging voltage, or a higher-valued, candidate charging current for an entry halfway toward the end of the table (e.g., entry number 12) is selected when the measured electrode voltage is lower than the target charging voltage.
• a table such as Table 2 above, in which candidate charging currents are arranged in an increasing order, a lower-valued, candidate charging current for an entry halfway toward the beginning of the table (e.g., entry number 4) is selected when the measured electrode voltage is higher than the target charging voltage, or a higher-valued, candidate charging current for an entry halfway toward the end of the table (e.g., entry number 12) is selected when the measured electrode voltage is lower than the target charging voltage.
• next candidate charging current may be selected as a next sequential entry in the table (e.g., if entry number 1 was selected for the first iteration, entry number 2 may be selected for the next iteration).
• Blocks 612, 613, and 614 may thereafter be performed for the next selected candidate charging current.
• a final charging current value for the electrode is set, in block 616.
• the final charging current value may be one of the last two candidate charging currents evaluated (e.g., during the last two search iterations), whichever yielded an electrode voltage measurement that was closest to the target charging voltage.
• the final charging current value may be a value that is between the last two candidate charging currents evaluated (e.g., halfway between or some other distance that is related to how close the last measured electrode voltage was to the target charging voltage).
• the final charging current value may be set, for example, by storing the final charging current value in a memory location that is accessible to the capacitive touch sensor (e.g., in data storage 212, FIG. 2).
• a validation process (not illustrated) may be performed, during which the electrode is again supplied with a current having the final charging current value for a duration equal to the final charging interval value.
• the validation process yields a measured electrode voltage within the target range (e.g., target voltage range 312, FIG. 3) and/or a measured voltage that is sufficiently close to the target charging voltage, the method may end.
• the validation process yields a measured electrode voltage that falls outside of the target range (e.g., target voltage range 312, FIG.
• the charging voltage and/or charging current searching processes may be repeated one or more times (e.g., with previously-determined final charging interval value(s) and/or final charging current value(s) excluded from the search). If, after a pre-defined number of repetitions, the validation process fails to produce a charging interval value and charging current value that yield an acceptable electrode voltage measurement, an error may be declared (e.g., an interrupt may be sent to system controller 102, FIG. 1).
• FIG. 7 is a flowchart of a method for configuring or reconfiguring the charging parameters for an electrode, according to another example embodiment.
• the method of FIG. 7 may be performed in conjunction with blocks 502 and/or 524 of FIG. 5.
• the method may begin, in block 700, by determining whether the configuration or re-configuration process is enabled or disabled. When the process is disabled, the method may end.
• the method may proceed to block 702, in which a target charging voltage is determined.
• the process of determining a target charging voltage may be performed as described previously in conjunction with block 602 of FIG. 6, which process is not repeated here for purposes of brevity.
• the current/interval pair search is an iterative process in which, during each iteration, the electrode is charged with a different current/interval pair, which includes a predefined, selectable charging current and a pre-defined, selectable charging interval.
• a set of pre-defined current/interval pairs may be accessible to the capacitive touch sensor (e.g., in data storage 212, FIG. 2).
• the set of pre-defined current/interval pairs may include from two to X values, for example.
• Table 3 Current/Interval Pair Table In Table 3, above, each current/interval pair is matched with a range of capacitances (i.e., a low capacitance value, C low, a high capacitance value, C high, and a middle capacitance value, C mid, between C low and C high.
• the range of capacitance values (i.e., from C low to C high) for each current/interval pair indicate a range of capacitances that may be measurable given the charging current and the charging interval.
• Table 3 The values in Table 3 were empirically determined by testing every possible combination of charging current and charging interval, determining the capacitance range for the tested current/interval pair, and eliminating current/interval pairs to generate a table in which any capacitance between a range of 0.495721 and 2874.386 picofarads may be detected, without including redundant or completely overlapping capacitance sub-ranges.
• the range of capacitances for each current/interval pair may slightly overlap the capacitance ranges of adjacent current/interval pairs, thus producing a table in which any capacitance within the desired range is detectable without significant redundancy.
• a current/interval pair table alternatively may include more or fewer than twenty-five values, the charging current and charging interval values may be different from those shown in Table 3, and/or the range of capacitances covered by the table may be different from that which is covered in Table 3.
• the current/interval pair search is performed as a binary search, in which a central current/interval pair is selected from the table during the first searching interval (e.g., a charging current of 31 microamps and a charging interval of 1 microsecond corresponding to entry number 13), and based on the results of the first iteration, a next current/interval pair is selected during the second iteration, where the next selected current/interval pair corresponds to an entry halfway toward the bottom or top of the table with respect to the central current/interval pair (e.g., one of the current/interval pairs corresponding to entry numbers 6 or 7 and 19 or 20, respectively). Subsequent iterations continue to be performed until the binary search converges on a final value.
• a central current/interval pair is selected from the table during the first searching interval (e.g., a charging current of 31 microamps and a charging interval of 1 microsecond corresponding to entry number 13)
• a next current/interval pair is selected during the second iteration, where the next
• the binary search would converge to a particular current/interval pair (or table entry number) in five iterations.
• the below description of blocks 704, 706, 708, and 710 will be described in accordance with an embodiment that uses a binary search to determine a current/interval pair. It is to be understood, however, that other searching methods alternatively may be used, in other embodiments.
• entries in a table of pre-defined current/interval pairs may be selected linearly (e.g., starting from entry number 1), or may be selected in some other sequence.
• the current/interval pair search process begins, in block 704, by selecting a candidate current/interval pair.
• a first selected candidate current/interval pair may correspond to a central current/interval pair (e.g., a charging current of 31 microamps and a charging interval of 1 microsecond corresponding to entry number 13 of Table 3, above).
• an electrode charging process may then be performed, by applying a charging current to the electrode for a duration of time that equal the candidate charging current and the candidate charging interval, respectively.
• an electrode measurement process may be performed during which the electrode voltage is measured.
• the singular electrode voltage measurement may then be evaluated, in block 708, or the charging and measurement processes may be repeated one or more times and a mathematical determination of the electrode voltage may be determined from the multiple electrode voltage measurements (e.g., an average of the multiple measurements).
• the electrode voltage measurement is compared with the target charging voltage (as determined in block 702) to determine whether the electrode voltage measurement is higher than or lower than the target charging voltage.
• the electrode voltage measurement also may be represented as an ADC count, and the comparison performed in block 708 may include comparing the ADC count corresponding to the target charging voltage with the ADC count corresponding to the electrode voltage measurement.
• the current/interval pair search process may be considered to be completed, for example, when a defined number of iterations have been performed in
• the current/interval pair search process may be considered to be completed when the last two iterations of the searching process resulted in electrode voltage measurements on either side of the target charging voltage.
• next searching iteration is initiated by again selecting a candidate current/interval pair in block 704.
• the next candidate current/interval pair is selected based on the comparison made in block 708.
• a lower-ordered, candidate current/interval pair for an entry halfway toward the beginning of the table (e.g., entry number 6 or 7) is selected when the measured electrode voltage is higher than the target charging voltage, or a higher-ordered, candidate current/interval pair for an entry halfway toward the end of the table (e.g., entry number 19 or 20) is selected when the measured electrode voltage is lower than the target charging voltage.
• next candidate current/interval pair may be selected as a next sequential entry in the table (e.g., if entry number 1 was selected for the first iteration, entry number 2 may be selected for the next iteration).
• Blocks 706, 708, 710 may thereafter be performed for the next selected candidate current/interval pair.
• an intermediate charging current, IQ, and an intermediate charging interval, To will have been determined as the charging current and the charging interval, respectively, of the finally selected current/interval pair.
• the current/interval pair search resulted in a selection of entry number 8 from Table 3, above, which corresponds to an lo of 3 microamps and a To of 2 microseconds.
• a measured electrode voltage will have been determined that corresponds to the finally selected
• the measured electrode voltage may be represented by an ADC count, ADCo, for example.
• ADCo ADC count
• a maximum ADC count in the system is 1024
• ADCo ADC count
• To ADCo
• a product of a desired charging current and a desired charging interval (herein “desired 7*7”) may be mathematically determined, in block 712.
• the desired 7*r may be determined according to the following equation:
• ADC 0 DD where ADC NUM is the number of possible ADC counts, and V DR op is a voltage difference between the supply voltage, VDD, and an upper voltage threshold (e.g., upper voltage threshold 310, FIG. 3).
• an upper voltage threshold e.g., upper voltage threshold 310, FIG. 3
• separating the desired charging current and the desired charging interval includes correlating the desired /T with a table of I*T ranges and associated charging intervals, and selecting the desired charging interval as the charging interval associated with an I*T range with which the desired I*T correlates.
• Table 4 an example of a pre-defined /*r range/charging interval table is provided below as Table 4:
• an I*T range/charging interval table may include more or fewer entries and/or having different values may alternatively be used.
• the I*T range (min) values equal the associated charging interval (e.g., one of values 0.5 through 32 microseconds in powers of two) multiplied by the minimum available charging current (e.g., 1 microamp).
• the I*T range (max) values equal the associated charging interval (e.g., one of values 0.5 through 32 microseconds in powers of two) multiplied by the maximum available charging current (e.g., 63 microamps).
• some of the valid I*T ranges overlap, which means that some desired I*T values may yield the same capacitance range.
• a desired I*T was determined to be 6.32
• correlation of the desired I*T with the I*T ranges of Table 4 indicates that the desired I*T value falls into any one of the first four I*T ranges (i.e., entries 1-4), which correspond to charging interval values of 0.5, 1 , 2, and 4 microseconds, respectively.
• a search for a valid I*T region i.e., an I*T region that correlates with the desired 7*7
• an entry may be selected that matches the shortest desired charging interval value first.
• a desired I*T of 6.32 falls within the I*T range of the first entry (i.e., an I*T range of 0.5 to 31.5), and therefore the charging interval for the first entry (i.e., 0.5
• microseconds may be determined to be the desired charging interval value (i.e., the charging interval value that is separated from the desired 7*7).
• an 7*rrange other than the 7* ⁇ range corresponding to the shortest charging interval may be selected (e.g., an 7* ⁇ range that correlates with the desired 7* ⁇ that corresponds to the longest charging interval, or entry 4 with a charging interval of 4 microseconds in the above-given example).
• a final charging current value and a final charging interval value for the electrode is set.
• the final charging current value and the final charging interval value may be set, for example, by storing the desired charging current value and the desired charging interval value in memory locations that are accessible to the capacitive touch sensor (e.g., in data storage 212, FIG. 2). The method may then end.
• various embodiments of methods and apparatus for configuring a capacitive touch sensor device have been described above.
• the various embodiments enable individual charging current and charging interval settings to be established for each of multiple electrodes (e.g., electrodes 106-108, FIG. 1) during an initial automatic configuration process, and /or during automatic re-configuration processes that may be performed for any one or more of the system's electrodes.
• An embodiment includes a capacitive touch sensor comprising an analog-to- digital converter (ADC) and a controller, operatively coupled to the ADC.
• the ADC is adapted to receive an analog voltage signal from an electrode, and to sample the analog voltage signal in order to produce a plurality of digital values.
• the controller is adapted to perform a first charging process by supplying the electrode with a first charging current for a first charging interval, and to determine, based on at least one of the plurality of digital values, whether a first electrode voltage value meets a criteria.
• the controller is adapted to perform a configuration process that results in setting a second charging current and a second charging interval for the electrode which, in response to performing a second charging process, results in a second electrode voltage value that is more likely to meet the criteria.
• the controller is adapted to perform the configuration process by performing an iterative process in which the electrode is charged for a plurality of charging intervals and with a plurality of charging currents to determine the second charging interval and the second charging current.
• the controller is further adapted to configure the electrode by storing the second charging current and the second charging interval for the electrode for use during one or more subsequent charging processes.
• the controller is adapted to perform the iterative process by supplying a fixed charging current to the electrode for a plurality of charging intervals in order to determine the second charging interval, and supplying a plurality of charging currents for the second charging interval to determine the second charging current.
• the controller is adapted to supply the fixed charging current to the electrode for the plurality of charging intervals by iteratively selecting, from a first pre-defined table, different charging intervals for which the charging current is to be supplied, and to supply the plurality of charging currents to the electrode for the second charging interval by iteratively selecting, from a second pre-defined table, different charging currents to be supplied to the electrode for the second charging interval.
• the controller is adapted to select the different charging intervals from the first pre-defined table and to select the different charging currents from the second pre-defined table using binary searching processes.
• the controller is adapted to perform the iterative process by charging the electrode using a plurality of candidate charging current/interval pairs in order to determine the second charging current and the second charging interval.
• the controller is adapted to determine the plurality of candidate charging current/interval pairs by iteratively selecting, from a pre-defined table, different charging current/interval pairs to be used in charging the electrode.
• the controller is adapted to select the different charging current/interval pairs from the predefined table using a binary searching process.
• the capacitive touch sensor further comprises a current source, operatively coupled to the controller, and adapted to supply the first charging current to the electrode for the first charging interval, and a timer, operatively coupled to the controller and to the current source, and adapted to provide a timing signal to the current source that enables the current source to initiate supply of the first charging current at a beginning of the first charging interval and to terminate supply of the first charging current at an end of the first charging interval.
• the capacitive touch sensor further comprises data storage, operatively coupled to the controller, and configured to store values representing the first charging current, the first charging interval, the second charging current, and the second charging interval.
• Another embodiment includes a capacitive touch sensor device comprising an electrode, and a capacitive touch sensor, operatively coupled to the electrode.
• the capacitive touch sensor is adapted to perform a first charging process by supplying the electrode with a first charging current for a first charging interval, to measure a first voltage resulting from the first charging process, and to determine, based on the first voltage, whether a first electrode voltage value meets a criteria.
• the capacitive touch sensor device is adapted to perform a configuration process that results in setting a second charging current and a second charging interval for the electrode which, in response to performing a second charging process, results in a second electrode voltage value that is more likely to meet the criteria.
• the capacitive touch sensor further comprises one or more additional electrodes, wherein the capacitive touch sensor also is operatively coupled to the one or more additional electrodes, and is adapted to perform the configuration process for the electrode and each of the one or more additional electrodes so that a different charging current and a different charging interval may be set for the electrode and each of the one or more additional electrodes.
• Yet another embodiment includes a method for configuring a capacitive touch sensor device.
• the method comprises the steps of performing a first electrode charging process by supplying a first electrode with a first charging current for a first charging interval, measuring a first voltage of the first electrode, which results from the first charging process, and determining, based on the first voltage, whether a first electrode voltage value meets a criteria.
• the method includes determining a second charging current and a second charging interval for the first electrode that results in a second electrode voltage value that is more likely to meet the criteria.
• the method also includes storing the second charging current and the second charging interval for use during a subsequent electrode charging process of the first electrode.
• determining whether the first electrode voltage value meets the criteria comprises determining whether the first electrode voltage value falls within a target voltage range.
• determining the second charging current comprises supplying a fixed charging current to the first electrode for a plurality of charging intervals by iteratively selecting, from a first pre-defined table, different charging intervals for which the fixed charging current is to be supplied to the first electrode, and determining the second charging current comprises supplying a plurality of charging currents to the first electrode for a fixed charging interval by iteratively selecting, from a second pre-defined table, different charging currents to be supplied to the first electrode for the fixed charging interval.
• the steps of iteratively selecting the different charging intervals from the first pre-defined table and iteratively selecting the different charging currents from the second pre-defined table are performed using binary search processes.
• determining the second charging current and determining the second charging interval comprises iteratively selecting, from a pre-defined table, different charging current/interval pairs, and charging the first electrode using each of the different charging current/interval pairs.
• the steps of performing, measuring, determining, and storing are repeated for one or more additional electrodes, so that a different charging current and a different charging interval may be set for the electrode and each of the one or more additional electrodes.

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