Friday, 5 July 2013
4 wire resistive touchscreen HW emulator
While the TSC is on its way, I couldn't just move on with tinkering the ADC drivers without knowing if I've accidentally broken the TSC ones.
So here comes the hardware 4 wire touchscreen emulator!
Folks at #beagle-gsoc were pretty helpful in guiding me on how to test the TSC without the TSC.
"evtest /dev/input/touchscreen0 " runs a great utility detecting touchscreen input.
And the hardware is just resistors/potentiometers.
I googled and after a while. This is what I could come up with. Note : Dont use 100K ohm resistors. I tried. It doesnt work. :p
These are in the range of 10K ohms.
The circuit is kinda like.
AIN0 --- Pot1 Pot4 ---AIN2
AIN1 --- Pot2 Pot5--- AIN3
evtest gives great output. pot 3 controls the pressure value.
pot 1/2/4/5 control X/Y coordinates.
Who needs a touchscreen when you have potentiometers! :)