Touch Screen, 4 wire Resistive

INTRODUCTION:
This resistive touch screen can be used with a stylus or fingertip and is easy to use with a microcontroller. You can put it over a paper overlay for a touch control panel or attach it to an LCD to DIY a touch-activated display.

A resistive touch screen is constructed with two transparent layers coated with a conductive material stacked on top of each other. This is 4-wire resistive touch screen. When pressure is applied by a finger or a stylus on the screen, the top layer makes contact with the lower layer. When a voltage is applied across one of the layers, a voltage divider is created. The coordinates of a touch can be found by applying a voltage across one layer in the Y direction and reading the voltage created by the voltage divider to find the Y coordinate, and then applying a voltage across the other layer in the X direction and reading the voltage created by the voltage divider to find the X coordinate.

Once a touch is detected, the controller reads the x and y coordinates of the touch. To read the coordinates, the pins are configured as previously described to drive the X lines and set the Y sense pin as analog ADC inputs. Four ADC conversions are taken and averaged together to obtain the x coordinate reading. The same process is repeated to obtain the y coordinate.