i have fiddled around a bit with the coordinates.

it's not 100% exact, but it's waay better than only doing div 16 and really
sufficient when used on hardware.

Code:
touchxy.px := (touchxy.px div 14) - 19;
touchxy.py := (touchxy.py div 19) - 10;
this gives me the best result, the X/Y-range goes from 0..251:0..191.

Tested with no$gba and my phat NDS.
Please note that your emulator will probably give slightly different results.

i hope this will get obselete soon :)

oh and... does anybody actually need this stuff? 100+ views but nobody's posting.