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Capacitive touchpad method using MCU GPIO and signal processing

  • US 8,212,159 B2
  • Filed: 05/11/2009
  • Issued: 07/03/2012
  • Est. Priority Date: 05/11/2009
  • Status: Active Grant
First Claim
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1. A machine-implemented method comprising:

  • using a processing unit to identify a maximum x-axis charge time from a plurality of x-axis charge times, the maximum x-axis charge time corresponding to a maximum x-axis sensor location;

    identifying a first adjacent x-axis charge time and a second adjacent x-axis charge time, the first adjacent x-axis charge time corresponding to a first adjacent x-axis sensor location adjacent to the maximum x-axis sensor location and the second adjacent x-axis charge time corresponding to a second adjacent x-axis sensor location adjacent to the maximum x-axis sensor location;

    computing a first adjacent x-axis charge time ratio using the first adjacent x-axis charge time and computing a second adjacent x-axis charge time ratio using the second adjacent x-axis charge time;

    determining that the first adjacent x-axis charge time ratio is larger than the second adjacent x-axis charge time ratio;

    computing an x-axis position based upon the maximum x-axis charge time sensor location and the first adjacent x-axis charge time ratio;

    using the processing unit to identify a maximum y-axis charge time from a plurality of y-axis charge times, the maximum y-axis charge time corresponding to a maximum y-axis sensor location;

    identifying adjacent y-axis charge times, wherein the adjacent y-axis charge times correspond to adjacent y-axis sensor locations that are adjacent to the maximum y-axis sensor location;

    computing an adjacent y-axis charge time ratio based upon one of the adjacent y-axis charge times and computing a y-axis position based upon the maximum y-axis charge time sensor location and the adjacent y-axis charge time ratio; and

    mapping the x-axis position and the y-axis position to a contact location for a two-dimensional grid.

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