The gist of my problem is that I have a resistive touchscreen and a Raspberry Pi, and I need to make one talk to the other using a single ADC of some kind.
I have worked with an Arduino and I also know the basic concept behind a resistive touchscreen. However, I'm having some problems planning out how to attach it to the raspberry pi and I don't want to commit too much to parts unless I know how I'm going to do it. Basically, I need to put voltage across the x+ and x- leads, while measuring the y+ lead using the ADC, right? But then I have to switch leads and put voltage across the y+ and y- leads, and measure the x+ lead.
On an Arduino it's obvious how to do that, because the analog input pins can also serve as digital outputs. But I have no such luck with the Pi. I can wire up an ADC to the pi but I'm not really sure what ADC will do the job, since it seems to have to provide digital outputs as well. I'm looking at basic ADCs like the MCP3008 right now. Is it possible to control a resistive touchscreen with such a chip, and if so how? If not, what ICs do I need?
Also if you're going to suggest an IC, please stick to ones that can be found in PDIP packages. I know that's REALLY restrictive (a lot of the "touchscreen digitizer ADCs" I've seen are TSSOP/QFN only) but this is a small hobby for me, I'm working on a breadboard, and I don't really have the tools to use other packages.