Android Devkit Touch Screen Porting Guide

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About this Manual

This manual is intended to get Touch Screen working with Android DevKit. This wiki assumes that the touch screen driver is validated with a linux kernel image and filesystem. This wiki is applicable only to resistive touch screens.

Touch Screen Android Requirements

Android Framework expect five types of values are reported by the touch screen driver.

1. x coordinate
2. y coordinate
3. pressure
4. penup event
5. pendown event

The driver report two types of events

1. pen down event with x- cordinate, y-cordinate and pressure
2. pen up event with pressure value being zero

Android requires the x-cordinate and y-cordinate need to be calibrated.

EXAMPLE: ads7846 touch screen driver

Lets see what changes are done in the case of ads7846 touch screen integrated with the omap3evm.

static void ads7846_report_state(struct ads7846 *ts)
{
        struct ads7846_packet *packet = ts->packet;
        unsigned int Rt;
        u16 x, y, z1, z2;