Help triggering capacitive touch on a touchscreen!

[Teddy]

Hey guys!

I'm doing a project with the ioio, where i'm trying to basically get the board to trigger to touch on a capacitive touch screen, similar to https://www.youtube.com/watch?v=JDgDMBquBw0 and https://www.youtube.com/watch?v=z4eTjH4zjwE.

The problem I'm having is, when I hook up some wires to the digital out (and digital out + ground), what's generated is just insane. I have a similar setup to the second video, except for a penny, and the screen flashes constantly and not in any pattern.

Does anyone have any tips/ideas??

Thanks!

[Ytai Ben-Tsvi]

Are you using open drain?

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[Teddy]

I guess not? This is the first I've heard of it! How is it any different than anything else?! 

[Teddy]

So I did end up trying open drain, and it still didn't do anything :(

It's pretty much a solid touch that its treated as, without any "off" at all!

[Ytai Ben-Tsvi]

When working in open drain, the pin will be pulled to GND whenever you write(false) and will be left floating whenever you write(true) (as opposed to normal mode, where write(true) will pull the pin to 3.3V).

I'd imagine that this technique might be sensitive to wire lengths and such, so you'd need to research / experiment it.