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Electronic circuit and method to account for strain gauge variation

  • US 10,013,081 B1
  • Filed: 04/04/2017
  • Issued: 07/03/2018
  • Est. Priority Date: 04/04/2017
  • Status: Active Grant
First Claim
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1. An apparatus for sensing user input provided on an exterior surface of an electronic device, comprising:

  • a first strain gauge configured to couple with a housing of an electronic device;

    an amplifier electrically coupled to the first strain gauge and configured to generate collections of analog signals by amplifying an electrical property of the first strain gauge;

    an analog-to-digital converter electrically coupled to the amplifier and configured to receive the collections of analog signals from the amplifier and generate collections of digital signals that are representations of the collections of analog signals generated by the amplifier; and

    an electronic circuit electrically coupled to the analog-to-digital converter and configured to receive digital signals from the analog-to-digital converter, the electronic circuit further configured to;

    (i) identify a value of a first signal received from the analog-to-digital converter in response to a signal generated by the first strain gauge in response to user input that interacts with the housing;

    (ii) determine that the identified value of the first signal exceeds a first threshold value, the first threshold value being based on a maximum value associated with the analog-to-digital converter;

    (iii) adjust an amplification level of the amplifier in response to determining that the identified value of the first signal exceeds the first threshold value;

    (iv) receive a first collection of digital signals generated by the analog-to-digital converter in response to signals generated by the first strain gauge in response to user input that interacts with the housing;

    (v) in response to determining that each of the first collection of digital signals exceed, for a specified period of time, a second threshold value that is less than the first threshold value, define, using at least a subset of the first collection of digital signals, an updated baseline output value for the analog-to-digital converter, wherein the digital signals in the first collection of digital signals are generated over the course of a pre-determined period of time ending at or near a current time; and

    (vi) indicate, based on a comparison of the updated baseline output value for the analog-to-digital converter to a digital value generated by the analog-to-digital converter in response to user interaction with the first strain gauge, that a first type of user input has been received.

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