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
               |               |
                    Pot 3
               |               |
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! :)

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