input/Touch_Pad/touch_area/source/template.c

/*---------------------------------------------------------------------------------

This demo uses the cross pannel resistance to calculate the area of touch contact
A higher value for "area" corresponds to a lower area of contact.  This can be used
to detect the difference between a pen or a finger press and to a certain extent the
relative pressure of the touch.

-- dovoto

---------------------------------------------------------------------------------*/
#include <nds.h>
#include <stdio.h>

//---------------------------------------------------------------------------------
int main(void) {
//---------------------------------------------------------------------------------

    //my experimental value for pen vs finger (higher value == lower area)
    const int threshold = 400;

    touchPosition touch;

    consoleDemoInit(); 

    int area = 0;

    while(1) 
    {

        scanKeys();

        touchRead(&touch);

        area = touch.px * touch.z2 / touch.z1 - touch.px;

        iprintf("\x1b[10;0HTouch x = %04i, %04i\n", touch.rawx, touch.px);

        iprintf("Touch y = %04i, %04i\n", touch.rawy, touch.py);

        iprintf("Touch Area (pressure) %04i\n", area);

        if(keysHeld() & KEY_TOUCH)
            iprintf("Last touched by: %s", area > threshold ? "pen   " : "finger");

        swiWaitForVBlank();
    }

    return 0;
}