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Determining touch locations and forces thereto on a touch and force sensing surface

  • US 9,430,107 B2
  • Filed: 04/16/2014
  • Issued: 08/30/2016
  • Est. Priority Date: 03/30/2012
  • Status: Active Grant
First Claim
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1. A method for decoding multiple touches and forces thereof on a touch sensing surface, said method comprising the steps of:

  • scanning a plurality of channels aligned on an axis for determining self-capacitance values of each of the plurality of channels;

    comparing the self-capacitance values to determine which one of the channels has a local maximum self-capacitance value, wherein left and right slope values are determined for the at least one self-value, wherein;

    the left slope value is equal to the at least one self-value minus a self-value of a channel to the left of the at least one channel, andthe right slope value is equal to the at least one self-value minus a self-value of a channel to the right of the at least one channel;

    wherein when the left slope value is greater than zero (0) and the right slope value is less than zero (0), then determine a local maximum self-capacitance value and return to the step of scanning the plurality of nodes of the at least one channel, and when no then continue to next step;

    wherein when a ratio between a positive left slope value and a positive right slope value is greater than a predefined threshold, then determine a local maximum self-capacitance value and return to the step of scanning the plurality of nodes of the at least one channel, and when not then continue to the next step;

    wherein when a ratio between a negative left slope value and a negative right slope value is less than a predefined threshold, then determine a local maximum self-capacitance value and return to the step of scanning the plurality of nodes of the at least one channel, and when not then continue to the next step;

    wherein when there is another self-value, then return to the step of determining left and right slope values;

    scanning a plurality of nodes of at least one channel having local maximum self-capacitance value for determining mutual values of the nodes;

    comparing the mutual values to determine which one of the nodes has the largest mutual capacitance value, wherein the node having the largest mutual capacitance value on the local maximum self-capacitance value channel is a potential touch location; and

    determining a force at the potential touch location from a change in the mutual capacitance values of the node at the potential touch location during no touch and during a touch thereto.

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