FAQ: Why you can't use your headunit or GPS touchscreen to control your PC
This question comes up over and over:
Can I use the touchscreen on my (AVIC, Headunit, GPS unit, dashboard LCD) to control my computer?
Short attention span answer: No.
Sure, it looks like a good idea. Why can't I use the touchscreen on my GPS unit to control my computer? It has a video input I could see my computer screen on.
Or, your car came with a built in screen, say with nav on it or with system information on it like the Prius has. It has a touchscreen, why can't you use it to control your PC?
The answer is that you aren't thinking it through very carefully. The most common type of touch screen uses a 4 or 5 wire resistive coating that produces a particular voltage when you touch it. There is a controller that measures this voltage and relays the information to a control device -usually a hardware based computer that interprets that information and processes accordingly.
What that means is the touch screen is already in use by another computer -either your GPS unit or your car's computer system. In order for you to use it to control your PC, you are going to have to figure out a way to either switch the touchscreen connection or share it between your PC and the other computer.
You'll have to open up the unit with the touchscreen - the GPS or the car nav system or the headunit, hack into the wires on the system, then connect those wires to your PC. Will it work? Maybe. Or maybe not. Or maybe you'll fry your headunit/GPS/car nav system. Or the PC. Or both.
Is it impossible? No. It CAN be done. This guy did. But if you don't understand why you can't share the touch screen in the first place, you don't have the have the necessary skills to do so.