Hardware Touchscreen

From OpenTom

Contents 1 General 2 Calibration 3 Using the touch screen 4 Future

General

• see Hello world example
• The touch screen must be calibrated if you replace ttn (which does calibration for you). The calibration data is stored in flash memory, and can be accessed (on OpenTom 0.0.2) by reading the file /mnt/flash/sysfile/cal .
• The touch screen is available on character device 254:0 (should be /dev/ts)

Calibration

Here is an exemple for the TomTom One. For other models, it may be necessary to swap horizontal and vertical calibration data.

 static MATRIX cal_data;
 ioctl(tsfd,TS_GET_CAL,&cal_data);
 // Read calibration data in flash memory
 FILE * cal_file = fopen ("/mnt/flash/sysfile/cal","rb");
 if ((cal_file == NULL) || (fread (&cal_data.xMin, sizeof(int), 4, cal_file) != 4))
 {
    perror ("Reading calibration file");
    exit (1);
 }
 fclose (cal_file);
 ioctl(tsfd,TS_SET_CAL,&cal_data);
 ioctl(tsfd,TS_SET_RAW_OFF,NULL);

Using the touch screen

Try something like this (written freehand, maybe contains small errors):

// Event struct
TS_EVENT ev;

// Open the device
int ts = open("/dev/ts", O_RDONLY | O_NONBLOCK);

// Read a dataset, store it in ev
if ( read(ts,&ev,sizeof(TS_EVENT)) == sizeof(TS_EVENT) ) {
 ...
}

// Better flush the device, otherwise TTs navigation software would use waiting data
while ( read(ts,&ev,sizeof(TS_EVENT)) == sizeof(TS_EVENT) ) {}

// Clean up...
close(ts);

TS_EVENT can be found in barcelona/Barc_ts.h and looks like this:
typedef struct {
 short pressure; // 255 -> pressed, 0 -> released
 short x;
 short y;
 short pad;
} TS_EVENT;

Also check Tslib.

Future

Check if device /dev/input/event0 provides raw "input_event"s, convertible from raw using routines similar to these found in the toolchain-kernel-diff (see tomtom.com/gpl) using calibration-data from /mnt/flash/sysfile/cal.