The boards I made in 2013 for resistive touch screens didn't work very well, barely got by, because the xMega couldn't measure higher than VCC/1.6, so "full scale" was just over 2/3 of the way.
Now, it's time to do it again, perhaps for SAM parts this time, haven't decided for sure. Since the Reference voltage can't be higher than VCC-0.6v, I thought I'd use a diode to generate a reference .7v below VCC. Of course, the reference input to the processor is pretty high impedance... Oh, use the touch panel itself as a pull down!
What do you guys think of this?
To measure "Y," you have to pull B and E low, set A high. Now the reference, as well as the top of the screen are 1 diode drop below AVCC, and you can measure C or F.
To measure "X," you pull A and F low, set B high. Now the reference, as well as the side of the screen are 1 diode drop below AVCC and you can measure D or E.
To turn the whole works off and not draw any current, set A and B both high.
Any better ideas?
Any idea where I can find 2.8 inch "Transflective" TFT displays in quantities of 1 to 10?
Anybody know, if you want it cooler, do you turn the air conditioner "up" or "down"?
Oh. Yes. Probably don't need pins C and D.