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Low current four-wire interface for five-wire resistive touch-screen

  • US 6,278,444 B1
  • Filed: 08/21/1998
  • Issued: 08/21/2001
  • Est. Priority Date: 08/21/1998
  • Status: Expired due to Fees
First Claim
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1. An interface converter to couple a five-wire touch-screen to a four-wire interface, the interface converter comprising:

  • a current injection device, wherein said current injection device supplies a constant current to an outer screen member of said five-wire touch-screen when said five-wire touch-screen is coupled to said interface converter and said five-wire touch-screen is compressed;

    a logic element coupled to said four-wire interface, said logic element sensing a mode of operation of said four-wire interface;

    a switching element coupled to said logic element, wherein said switching element routes a reference voltage from said four-wire interface to said current injection device when said four-wire interface is coupled to said interface converter, wherein said constant current is based on said reference voltage;

    a plurality of current converters coupled to a set of four inner screen member electrodes of said five-wire touch-screen when said five-wire touch-screen is coupled to said interface converter, wherein said plurality of current converters convert a plurality of position proportional currents to a plurality of position proportional voltages; and

    a logic amplifier coupled to said plurality of current converters, wherein said logic amplifier outputs a first voltage and a second voltage, wherein said first voltage is proportional to a x-coordinate of a five-wire touch-screen compression point and said second voltage is proportional to a y-coordinate of said five-wire touch-screen compression point, wherein said first and second voltages are routed to said four-wire interface when said four-wire interface is coupled to said interface converter.

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