If you purchased the version of the backpack with touch support, you will receive a board with extra circuitry for a resistive touch screen decoder. The circuit is an AR1100 USB resistive touch driver, so it basically just uses the same USB port you use to power, but for the data

The AR1100 shows up like a USB mouse, it works on all operating systems as the computer doesn't even know its a touch screen, it just thinks its a mouse! You can adjust the AR1100 to consider itself a Touch Digitizer, supported by many but possibly not all computers.

You can also re-calibrate the touch screen. We do calibrate it with the 800x480 5" screens but we recommend re-calibrating it if you feel like its not precise enough for your tastes.

The software is Windows only, but you only have to configure/calibrate the touch controller once, then it can be used on any computer!

All of this happens with the AR1100 software. We have a tutorial specifically on using that software over here, so please go there to learn all about it!