Interfacing any touch screen with AT91RM9200

Hi all, Now we are in study phase in analyzing to identify the microcontroller which is having in-build Ethernet port, memory interface (say CF) and USB port. Now we chose AT91RM9200 tha is the one which is having all these options. Could we interface any touch screen display with this microcontroller? If yes, how we have to interface it. My advance thanks to you.

with regards marans

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Tamilmaran S
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Yes, you can interface to any touchscreen. How depends on the touchscreen.

I am using the AT91RM9200 with a resistive touchscreen and have a touchscreen controller (Gunze AHL-71) on my board. This controller connects to the CPU through a serial port. So all my software has to do is decode the strings sent by the touchscreen controller.

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Your device doesn't have an ADC on board so you'll need extra parts to drive a resistive touch screen yourself. Don't even think about driving a capacitive screen yourself (in fact don't use capacitive screens anyway because they are temperamental and only any use if you are in a very harsh environment.)

Lot's of places make controllers to convert to serial, I've used 3M's with no problems and I've briefly tried the Hampshire Company Sharc 12 controller which seems to be very good. They also make ICs in various packages which are not very expensive. I bought my stuff through Review Displays

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and they've been pretty helpful especially during our capacitive screen debacle - long story.

Unless you are set in stone with your processor choice then the Sharp 79524 meets all your needs and has a built in touch screen interface and LCD controller as well. The 7A404 is an ARM9 device, if you want the extra speed, which does the same thing. I'm currently using the 79524 and its own controller to drive my 3M 4-wire resistive screen and it works great. You have to work out your own drivers and calibration routines but Sharp do an excellent application note -

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- which is very good to read even if you don't use the Sharp device because it explains a lot about touch screens (well resistive ones anyway).

Reply to
Tom Lucas











A very good architecture is the EP9315, you have all you need with an ID interface. Aother model is available: EP9312. Those intgrate also matrix keyboard driver (8*8) and the evaluation board includes what yo need.

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