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Localizing an electrostatic stylus within a capacitive touch sensor

  • US 9,927,909 B2
  • Filed: 10/22/2015
  • Issued: 03/27/2018
  • Est. Priority Date: 08/30/2010
  • Status: Active Grant
First Claim
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1. An active stylus configured to operate with a capacitive touch sensor, the active stylus comprising:

  • an electrode configured to both receive and transmit signals, and configured to electrostatically couple with the capacitive touch sensor;

    a switch, coupled with the electrode, that is configured to multiplex a relatively large voltage and a relatively small current, wherein the switch is configured to transmit a voltage to the electrode in a transmission mode, and to receive a current from the electrode in a receiving mode;

    a conductive tip for receiving current from the electrode through the switch, and for transmitting voltage that is coupled through the switch to the electrode;

    a microcontroller configured to determine at least one position of the active stylus with respect to locations on the capacitive touch sensor based on a first signal received from the capacitive touch sensor in a first timeslot, and to report the at least one position of the active stylus in a second timeslot allocated for reporting the at least one position to the capacitive touch sensor that differs from the first timeslot; and

    an internal power source to provide power to at least the microcontroller.

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