www.micro-examples.com : TouchClock

Design your own GLCD Touch Clock

TouchClock : a PIC18 GLCD touchscreen clock

A short video clip is sometimes better than a long explanation :

The idea of this project is to use a graphic LCD with a touchscreen and a built-in sprite editor to design your own clock, and shows how to connect a resistive touchscreen directly to a PIC with no additional hardware.

This project also includes a ready-to use touchscreen library for PIC

Circuit Schematic

This project is designed to run on an EasyPIC3 development board, so no circuit schematic is available.

This is how to connect the 4-wires resistive touchpanel directly to the PIC :

How the library reads the X raw coordinate of a touch  :

• X+ and X- are in high Z : RA0 and RA2 are inputs
• Y+ is set to +5V : RA3 is output high
• Y- is set to 0V : RA1 is output low
• X+ voltage is read by ADC
• Y+ is set to 0V : RA3 is output low
• Y- is set to 5V: RA1 is output high
• X- voltage is read by ADC and averaged with X+ value, the result is the raw X coordinate.
• The same is then done to read the Y coordinate, please see TSlib.c file in .ZIP file below.

X and Y raw coordinates are then adjusted using calibration coordinates to get X and Y coordinates in pixel.

C Source code

Since this project has multiple source files, source code is not expanded here : please download archive file below.

Download project

Download TouchClock-project.zip file for mikroC : File:TouchClock-project.zip

Includes :

• mikroC PRO project files for PIC18F4620, should work also with most PICs
• TouchClock C source code with resistive touchscreen library
• TouchClock .HEX files

Discussion and Comments