ECE 4760: Final Project

LED Sketchpad


Qingjun Wang (

Yun Qing (

Zhiyong Meng (

"An LED Sketchpad for painters and writers"

project soundbyte

In this project we built a sketchpad based on LED matrix display with microcontroller and resistive touch screen control. We used a single point resistive touch screen to detect the user’s gesture and microcontroller’s analog/digital converter (ADC) ports collects the data and convert it to coordinates. We designed a LED drive circuit with shift registers and 3 to 8 decoders to make 4 8x8 LED matrix able to display the map we programed in the microcontroller. We calibrated the touch screen with LED matrix, and finally achieved that the matrix display the same gesture user draws on the touch screen. The sketchpad was built with Write/Erase/All Clear modes, which was shifted with 3 buttons. The LED matrix displays exactly what the user draw on touchpad instantly.

The main part of the device is four 8x8 led matrixes, which form a 16x16 big screen with 256 pixels, and a 4-wire resistive touch screen. The ATmega 1284p microcontroller get the coordinates from the touch screen and transfer the data to the LED matrix. We used two 74HC595 shift registers and two 74HC138 3to8 decoder to build the led power drive and makes the wires as simple as possible. Three buttons are built to set the sketchpad into write/erase/clear mode.


The finished product.