AUTOMATIC LOW NOISE FREQUENCY SELECTION
First Claim
1. A circuit for automatically selecting a low noise frequency for use in a device comprising:
- a plurality of sense channels, each sense channel configured to receive a signal from a touch sensor panel;
a summing circuit coupled to the plurality of sense channels and configured to generate a sum of the signals;
a pair of magnitude circuits coupled to the summing circuit, one of the pair of magnitude circuits coupled to the summing circuit through a first mixer configured for demodulation with an in-phase (I) component of a demodulation frequency so as to calculate an in-phase magnitude value corresponding to an amount of noise at the demodulation frequency, and the other of the pair of magnitude circuits coupled to the summing circuit through a second mixer configured for demodulation with a quadrature (Q) component of the demodulation frequency so as to calculate a quadrature magnitude value corresponding to the amount of noise at the demodulation frequency; and
frequency selection logic coupled to the pair of magnitude circuits and configured to select without intervention from a processor the demodulation frequency as a low noise frequency if the amount of noise is lower than an amount of noise at another demodulation frequency, wherein the processor is configured to identify one or more touch events on the touch sensor panel.
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Abstract
Automatic low noise frequency selection for a touch sensitive device is disclosed. A low noise stimulation frequency can be automatically selected by device logic without intervention of the device processor to stimulate the device to sense a touch event at the device. The device logic can automatically select a set of low noise frequencies from among various frequencies based on the amount of noise introduced by the device at the various frequencies, where the frequencies with the lower noise amounts can be selected. The device logic can also automatically select a low noise frequency from among the selected set as the low noise stimulation frequency. The device logic can be implemented partially or entirely in hardware.
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Citations
16 Claims
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1. A circuit for automatically selecting a low noise frequency for use in a device comprising:
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a plurality of sense channels, each sense channel configured to receive a signal from a touch sensor panel; a summing circuit coupled to the plurality of sense channels and configured to generate a sum of the signals; a pair of magnitude circuits coupled to the summing circuit, one of the pair of magnitude circuits coupled to the summing circuit through a first mixer configured for demodulation with an in-phase (I) component of a demodulation frequency so as to calculate an in-phase magnitude value corresponding to an amount of noise at the demodulation frequency, and the other of the pair of magnitude circuits coupled to the summing circuit through a second mixer configured for demodulation with a quadrature (Q) component of the demodulation frequency so as to calculate a quadrature magnitude value corresponding to the amount of noise at the demodulation frequency; and frequency selection logic coupled to the pair of magnitude circuits and configured to select without intervention from a processor the demodulation frequency as a low noise frequency if the amount of noise is lower than an amount of noise at another demodulation frequency, wherein the processor is configured to identify one or more touch events on the touch sensor panel. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for automatically determining a low noise frequency for demodulating a signal, comprising:
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selecting a plurality of demodulation frequencies at which low noise appears in a signal received from a touch sensor panel, wherein the low noise is lower than an amount of noise appearing in the signal at another demodulation frequency; calculating a plurality of noise magnitudes at the selected plurality of demodulation frequencies, each of the plurality of noise magnitudes based on an amount of noise in the signal at the corresponding demodulation frequency; and determining a low noise magnitude and the corresponding demodulation frequency, the low noise magnitude being lower than a noise magnitude at another demodulation frequency and the determined demodulation frequency being used to generate further signals, wherein the selecting, the calculating, and the determining are without intervention of a processor configured to identify one or more touch events on the touch sensor panel. - View Dependent Claims (8, 9, 10, 11)
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12. A touch sensitive device comprising:
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at least one sense channel configured to sense a touch event at the device; scan logic couplable to the at least one sense channel and configured to perform a scan sequence on the device to determine the occurrence of the touch event; and frequency selection logic couplable to the scan logic and configured to select, without intervention from a processor configured to identify the touch event, a low noise frequency to be used during the scan sequence, the low noise frequency being a frequency at which an amount of noise is lower than an amount of noise at another frequency, and the low noise frequency being selectable from among a plurality of signal frequencies. - View Dependent Claims (13, 14, 15, 16)
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Specification