Capacitive sensor filtering apparatus, method, and system
First Claim
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1. A method for operating a capacitive sensor, comprising:
- providing a sensor electrode;
periodically exciting the sensor electrode and thereby periodically generating an electric field about the sensor electrode and a capacitance between the sensor electrode and a reference potential;
periodically determining in the time domain values of capacitance between the sensor electrode and the reference potential;
transforming a rolling sample of the periodically-determined values of capacitance from the time domain to a plurality of data signals in the sequency domain using a Walsh-Hadamard Transform, each of the data signals in a corresponding sequency bin resulting from the Walsh-Hadamard Transform and each of the data signals comprising values related to capacitance for corresponding samples of the rolling sample;
analyzing in the sequency domain at least one of the plurality of data signals in the corresponding sequency bin; and
determining whether a touch event has occurred based on the analysis of the at least one of the plurality of data signals in the corresponding sequency bin;
wherein the rolling sample is an n-point rolling sample including a current sample and n−
1 samples immediately preceding the current sample, wherein the n−
1 samples includes a last sample, and wherein n is an integer greater than or equal to 2 corresponding to a size of a Walsh matrix used in performance of the Walsh-Hadamard Transform.
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Abstract
A transform is used to transform raw capacitive sensor data from the time domain to the frequency or sequency domain. The transformed data falls into several signal bins. The transformed data in at least one of the signal bins is analyzed to determine whether a touch event or release event has occurred.
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Citations
17 Claims
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1. A method for operating a capacitive sensor, comprising:
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providing a sensor electrode; periodically exciting the sensor electrode and thereby periodically generating an electric field about the sensor electrode and a capacitance between the sensor electrode and a reference potential; periodically determining in the time domain values of capacitance between the sensor electrode and the reference potential; transforming a rolling sample of the periodically-determined values of capacitance from the time domain to a plurality of data signals in the sequency domain using a Walsh-Hadamard Transform, each of the data signals in a corresponding sequency bin resulting from the Walsh-Hadamard Transform and each of the data signals comprising values related to capacitance for corresponding samples of the rolling sample; analyzing in the sequency domain at least one of the plurality of data signals in the corresponding sequency bin; and determining whether a touch event has occurred based on the analysis of the at least one of the plurality of data signals in the corresponding sequency bin; wherein the rolling sample is an n-point rolling sample including a current sample and n−
1 samples immediately preceding the current sample, wherein the n−
1 samples includes a last sample, and wherein n is an integer greater than or equal to 2 corresponding to a size of a Walsh matrix used in performance of the Walsh-Hadamard Transform. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification