US 2010/0164905 A1Published application

Method of improved computation of touch coordinates for four-wire resistive touch screens

AssigneeSTMicroelectronics Asia Pacific Pte Ltd

InventorsBoon Loong Woo, Gopalakrishnan Srinivasan

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Abstract

A method for calculating coordinates and touch pressure on a four-wire resistive touch screen includes applying a voltage gradient across a flexible resistive sheet in a touch screen and measuring the voltage where the screen comes in contact with another screen via analog to digital couplings to the other screen. The touch pressure is acquired by applying a higher voltage potential to one resistive sheet and a lower voltage potential to the other sheet so that current flows between the sheets at the point of contact between the sheets. A voltage on each sheet is then measured at the point of contact shared by the sheets. The measured voltages are used to calculate the touch pressure.

Claims15

Dependent claims

A method of acquiring touch information from a touch screen, comprising:

supplying a first voltage across an upper resistive sheet of the touch screen by using a first voltage source and a second voltage, said voltage sources attached at opposing sides of the upper resistive sheet;
measuring a first voltage potential, the first voltage potential being on the upper resistive sheet at a touched location on the touch screen, the first voltage potential being measured through a contact between the upper resistive sheet and a lower resistive sheet at the touched location using a first coupling between the lower resistive sheet and an analog to digital converter;
calculating a first axis coordinate using the first voltage potential;
supplying a second voltage across the lower resistive sheet of the touch screen by using a third voltage source and a fourth voltage, said voltage sources attached at opposing sides of the lower resistive sheet;
measuring a second voltage potential, the second voltage potential being on the lower resistive sheet of the touch screen at the pressed location, the second voltage potential being measured through the contact between the lower resistive sheet and the upper resistive sheet at the touched location using a first coupling between the upper resistive sheet and the analog to digital converter;
and
calculating a second axis coordinate using the second voltage potential.

4 more elements

A method, comprising:

driving a first current across an upper resistive plate of a resistive touch screen from a first side of the top resistive sheet to an opposing second side of the top resistive plate;
measuring a first top sheet voltage potential from the first side of the top resistive plate;
measuring a second top sheet voltage potential from the second side of the top resistive sheet;
measuring a third top sheet voltage potential from a bottom resistive sheet at a point of contact between the top resistive sheet and the bottom resistive sheet while no current is driven across the bottom resistive sheet;
producing a first touch coordinate by applying the first top sheet voltage, second top sheet voltage, and third top sheet voltage to an analog to digital converter;
driving a second current across the bottom resistive sheet of the resistive touch screen from a first side of the bottom resistive sheet to an opposing second side of the bottom resistive sheet;
measuring a first bottom sheet voltage from the first side of the bottom resistive sheet;
measuring a second bottom sheet voltage from the second side of the bottom resistive sheet;
measuring a third bottom sheet voltage from the top resistive sheet at the point of contact between the top resistive sheet and the bottom resistive sheet while the first current is not driven across the top resistive sheet;
and
producing a second touch coordinate by applying the first bottom sheet voltage, second bottom sheet voltage, and third bottom sheet voltage to an analog to digital converter.

8 more elements

Dependencies are inferred from the claim text.