Computing stuff tied to the physical world

Touch screen

In Hardware on Dec 21, 2010 at 00:01

Steve Evans (tankslappa on the forum) emailed me recently to present some really exciting developments he’s been working on: a touch screen interface for the Graphics Board:


You’re looking at a little touch screen, placed over the Graphics Board, and as you can see, the size matches up surprisingly well.

Pretty fantastic result! And considerably more precise than I had expected.

He used the touch screen overlay of the Nintendo DS, which can be obtained from eBay. As it turns out, this can be hooked up using 2 digital + 2 analog I/O pins, which is exactly what’s still available on the unused two ports.

All that was needed, were 4 pull-down resistors:


The devil is in the details, though. very small details in fact:


Steve mentioned that it took a considerable amount of patience to get 4 wires soldered to that tiny flexible ribbon, with 0.5 mm between each connection. Clearly, a proper connector would have been a bit more convenient (though just as tiny).

Being resistive and analog, this whole thing needs to be calibrated:

Calibrate 1

The code for this has been added as a sample sketch called touchscreen.pde in the JeeLabs repository.

BTW, this is part of a new GLCDlib library, which I’ll describe in more detail tomorrow. Stay tuned!

  1. I think you only need 2 pull-down resistors, because you drive the other pins up or low anyway. So only the 2 analog pins need resistors.

    I also have a Nintendo touchscreen, and a tiny breakout board from SparkFun for easy connecting. But the tiny head of the connecting ribbon broke off, so now I have to try to solder it anyway…

  2. Congrats tankslappa very nice work!

    Cheers Rubu

  3. @PPK – Of course, thanks for that! To be honest I was so glad to have that connector soldered that once connected I just dived into the code and didn’t even think about seeing if there was anything I didn’t actually need!

    @Rubi – Thank you, it is rather fun… Now I have to do something useful with it :-)

  4. @TankSlappa Bloody hell you did it! Hug youuuuuuu! :-)

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