File content as of revision 2:c5085faf2aa5:

/* mbed library for resistive touch pads
 * uses 4 pins - 2 IO and 2 Analog

 * c 2011 Peter Drescher - DC2PD
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */


#include "mbed.h"
#include "SeeedStudioTFTv2.h"

//Serial pc(USBTX,USBRX,19200);

TouchScreen::TouchScreen(PinName xp, PinName xm, PinName yp, PinName ym)
{
    //font = NULL;
    // touch screen pins
    _xp = xp;
    _yp = yp;
    _xm = xm;
    _ym = ym;
    // default touch calibration
    // orientation     //      0      1      2      3
    x_off = 108000;  //  17252  16605 108755 108000
    y_off =  22000;  //  22330 105819  97167  22000
    pp_tx =   -291;  //    378    289   -390   -291
    pp_ty =    356;  //    261   -355   -239    356
}

int TouchScreen::readTouch(PinName p, PinName m, PinName a, PinName i)
{
    DigitalOut _p(p);
    _p = 1;
    DigitalOut _m(m);
    _m = 0;
    AnalogIn   _a(a);
    AnalogIn   _i(i); // this pin has to be high Z (DigitalIn may also work)
    wait_us(10);
    return _a.read_u16();
}

void TouchScreen :: getTouch(point& p)
{
    int y2 = readTouch(_xp,_xm,_yp,_ym);
    int x2 = readTouch(_yp,_ym,_xp,_xm);
    int y1 = readTouch(_xp,_xm,_yp,_ym);
    int x1 = readTouch(_yp,_ym,_xp,_xm);
    int xd = x1 - x2;
    int yd = y1 - y2;
    xd = (xd > 0) ? xd : -xd;
    yd = (yd > 0) ? xd : -xd;
    p.x = x1 + x2;
    p.y = y1 + y2;
            
    int z1          =  _xm;
    int z2          =  _yp;
    float rtouch    =  0;

    rtouch  = z2;
    rtouch /= z1;
    rtouch -= 1;
    rtouch *= (2046-p.x)/2;
    rtouch *= RXPLATE;
    rtouch /= 1024;
    p.z = abs(rtouch);
 }