Touchscreen Interfacing to the Computer

Touchscreens, like ordinary LCD and CRT monitors , use the standard 15-pin VGA interface to the video card. However, the touch signals are transmitted to the computer through a separate interface known as the touchscreen controller. Touchscreen controllers can use any of the following interfaces:

• Serial (RS-232) ” Some touchscreen monitors have an internal serial controller; others use an external serial controller. The internal serial controller might use a standard 9-pin serial cable or a special PS/2 “to “9-pin serial cable to connect the controller to a serial (COM) port on the computer, depending upon the monitor model. The external serial controller uses a controller with a built-in serial cable. See Chapter 8, "Input/Output Devices and Cables," for more details about serial ports and cables.

• USB ” A touchscreen monitor with an internal USB interface uses a standard USB cable to connect to a USB port on the computer. See Chapter 8 for more details about USB ports and cables.

• ISA card (also called PC Bus ) ” A touchscreen monitor with an external ISA card uses a special 9-pin cable to connect to the ISA card. The ISA card can be plugged into an ISA, EISA, or VL-Bus expansion slot. See Chapter 4, "The Motherboard and CPU," for more details about the ISA bus.