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;
}