METHOD AND APPARATUS TO MEASURE SELF-CAPACITANCE USING A SINGLE PIN
First Claim
1. A touch sensor system, comprising:
- at least one input port to receive an input signal from at least one electrode, the at least one electrode having a coupling capacitance;
an Analog to Digital Converter (ADC) having an ADC input and an ADC output;
a capacitor coupled to the ADC input;
a multiplexer (MUX) having multiple MUX inputs and a MUX output that is coupled to the ACD input, wherein the at least one port is coupled to one of the multiple MUX inputs;
a first switch for coupling a first reference voltage to a first input of the multiple MUX inputs;
a switch controller to control the first switch to apply the first reference voltage to the first input of the MUX; and
a sensor controller to receive a first digital value from the ADC output after application of the first reference voltage, and to determine a change in the coupling capacitance of the at least one electrode as a function of the first digital value.
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Accused Products
Abstract
A method for measuring capacitance in a sensor device using an internal reference circuit element(s), and without implementing additional circuitry and devices external to the sensor device, is described. In some embodiments a method uses an output pin of the sensor device and an internal reference capacitor of the sensor device to identify a touch applied to a touch point or electrode coupled to the touch sensor. The method applies reference voltages to charge the reference capacitor and measure a signal received from an electrode, wherein the touch sensor controls switching within the touch sensor to apply the reference voltages to the reference capacitor.
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Citations
20 Claims
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1. A touch sensor system, comprising:
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at least one input port to receive an input signal from at least one electrode, the at least one electrode having a coupling capacitance; an Analog to Digital Converter (ADC) having an ADC input and an ADC output; a capacitor coupled to the ADC input; a multiplexer (MUX) having multiple MUX inputs and a MUX output that is coupled to the ACD input, wherein the at least one port is coupled to one of the multiple MUX inputs; a first switch for coupling a first reference voltage to a first input of the multiple MUX inputs; a switch controller to control the first switch to apply the first reference voltage to the first input of the MUX; and a sensor controller to receive a first digital value from the ADC output after application of the first reference voltage, and to determine a change in the coupling capacitance of the at least one electrode as a function of the first digital value. - View Dependent Claims (2, 3, 4)
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5. A touch sensor apparatus, comprising:
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a reference circuit to measure electrical changes at a touch sensor electrode; a first switch to apply a first voltage signal to the reference circuit; a second switch to apply a second voltage signal to the reference circuit; and a measurement unit to measure a first change in electrical behavior of the touch sensor electrode after application of the first voltage signal, and to measure a second change in electrical behavior of the touch sensor electrode after application of the second voltage signal. - View Dependent Claims (6, 7, 8)
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9. A method, comprising:
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controlling a first switch to charge a reference capacitor to a first voltage level, the reference capacitor coupled to an input of an Analog to Digital Converter (ADC); receiving a first analog signal from a touch sensor electrode at the input of the ADC; converting the first analog signal to a first digital value provided at an output of the ADC; detecting a touch to the touch sensor device based on the first digital value. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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18. A computer-readable medium comprising instructions which, when implemented by one or more machines, cause the one or more machines to:
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control a first switch to charge a reference capacitor to a first voltage level, the reference capacitor coupled to an input of an Analog to Digital Converter (ADC); receive a first analog signal from a touch sensor electrode at the input of the ADC; convert the first analog signal to a first digital value provided at an output of the ADC; control a second switch to charge the reference capacitor to a second voltage level; receive a second analog signal from the touch sensor electrode at the input to the ADC; convert the second analog signal to a second digital value at the output of the ADC; and detect a touch to the touch sensor device based on the first and second digital values. - View Dependent Claims (19, 20)
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Specification