Interfacing with a touchscreen

Original Assignment

Interface the PIC with a surplus touchscreen from the LIMS lab and display (x,y) data on an LCD screen (see, e.g., C Example: Serial LCD or C Example: Parallel Interfacing with LCDs) or a PC (e.g., matlab or hyperterminal).

Spec sheet: [1] (Use the last .pdf under Reference Materials)

Overview

The goal of the project is to interface the PIC18F4520 with the 3M EX II 7720SC capacitive touchscreen. The spec sheet is located here: [2] (Use the last .pdf under Reference Materials). In addition, when a finger makes contact with the touchscreen, the X-Y coordinates will be displayed on a JHD 162A Parallel LCD (see C Example: Parallel Interfacing with LCDs).

On this page you will find the steps to do this on your own. This includes the code, circuit diagram, and other notes about creating the interface.

Circuit

Circuit schematic of connections between PIC, LCD, MAX232 and touchscreen

The image on the right is the circuit schematic showing the connections between all the components. An actual picture of the circuit is also shown.

The components required for implementing this circuit are:
1) PIC 18F4520
2) MAX232N Dual EIA-232 Driver/Receiver
3) EXII 7720SC (touchscreen controller chip)
4) JHD 162A Parallel LCD