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Self and mutual capacitance measurement in a touch screen

  • US 9,684,418 B1
  • Filed: 07/08/2014
  • Issued: 06/20/2017
  • Est. Priority Date: 04/16/2010
  • Status: Active Grant
First Claim
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1. A capacitance sensing device comprising:

  • a first plurality of capacitance sensing electrodes disposed along a first axis;

    a second plurality of capacitance sensing electrodes disposed along a second axis, the second axis substantially perpendicular to the first axis; and

    a controller configured to;

    measure a self capacitance of either;

    at least one of the first plurality of capacitance sensing electrodes or at least one of the second plurality of capacitance sensing electrodes and update a mutual capacitance baseline based on the measured self capacitance in a first mode,measure a mutual capacitance between at least one of the first plurality of capacitance sensing electrodes and at least one of the second plurality of capacitance sensing electrodes and update a self capacitance baseline based on the measured mutual capacitance in a second mode,identify a touch on the capacitance sensing device if the measured self capacitance is above a first self capacitance threshold and if the measured mutual capacitance is above a first mutual capacitance threshold so as to prevent reporting of false touches before one or more of the baselines is updated, and calculate a position of the touch on the capacitance sensing device based on one or more of the measured self capacitance and the measured mutual capacitance.

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