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Noise cancellation technique for capacitive touchscreen controller using differential sensing

  • US 8,493,356 B2
  • Filed: 01/07/2011
  • Issued: 07/23/2013
  • Est. Priority Date: 04/22/2010
  • Status: Expired due to Fees
First Claim
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1. A method of detecting one or more touch events on a touch sensitive device comprising;

  • a. receiving a plurality of channels, each channel having sensed data corresponding to the touch sensitive device;

    b. measuring a capacitance of each channel when no touch event is present on any of the plurality of channels, thereby determining a no touch baseline value for each channel;

    c. selecting one of the plurality of channels as a primary channel;

    d. selecting another of the plurality of channels as a references channel, wherein the reference channel is different than the primary channel;

    e. measuring a capacitance of the primary channel;

    f. measuring a capacitance of the reference channel;

    g. calculating a difference between the measured capacitance of the primary channel and the measured capacitance of the reference channel, thereby determining a measured difference;

    h. calculating a difference between the no touch baseline value for the primary channel and the no touch baseline value for the reference channel, thereby determining a baseline difference;

    i. calculating a difference between the measured difference and the baseline difference, thereby determining a delta from baseline for the primary channel and reference channel pair;

    j. repeating steps c-h for each channel in the plurality of channels so that each channel is selected as the primary channel; and

    k. determining one or more touch events from the delta from baselines calculated for all primary channel and reference channel pairs.

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