I have an ACX502ALM-7 series LCD+touchpanel combo. Google cannot find me a datasheet for it. Can any one of you? I'd like to possibly interface it (at least the touch screen part) to an Arduino Uno. Or do you know how to determine the pinout of the touchscreen? It's a 4-wire type.
The four signals of the touch screen are TOP, BOTTOM, LEFT and RIGHT. In the touchscreen there are two resistive films and an insulator gap which is closed by your finger pushing the screen. At each edge there is a conductive stripe. TOP and BOTTOM stripes are connected to the first resistive film. LEFT and RIGHT stripes are connected to the second resistive film.
You can detect the pinout easily with a multimeter by measuring RESISTANCE between each pin pair and finding out the pairs to which the pressing of the finger affects to. When you find a pin pair to which your finger has a definitive effect, slide your finger upwards and then sidewards to find out if that's the vertical or horizontal film pair.
Majority of touch screens use simple resistive matrices for interfacing. The four wires work like a pair of potentiometers. As the screen is touched, the resistance changes. You measure this with a couple of analog input pins on your Arduino. You can also use a multimeter to test.
See http://www.practicalarduino.com/projects/touch-control-panel for details.