74hc595-shift-register-8x8-led-matrix-display

Pakistan’s Independence Day 2012 – LED Matrix Display

I finally completed writing code for a Marquee Display and since I used the morning of 14th August to write this code, the least I could do was to celebrate Pakistan’s Independence Day as the first message and test for my code.

The code has DEFINE(s) for Display Length, Message Length, Speed Control and a Full-Size-AlphaNumeric-Font. Putting in a new message or updating via UART is also supported as the message array is built at run-time.

Complete code was written by me and this time, I didn’t Google once to see how others have done similar work. Now I think I will do some searching and compare my code with others.

Using AVR Atmega8, with an empty MAIN LOOP as everytihng is handles by a TIMER. The AVR sends commands via SPI to 2 Shift Registers (74HC595) which are connected in a way to overflow the data to the last register.

Here’s the Schematic; the resistors etc are not shown; I will probably put up a more detailed version sometime soon.

74hc595-shift-register-8x8-led-matrix-display
74HC595 Shift Registers driving an 8x8 Led Matrix Display

The 3 wires going up and out of the schematic are the SPI wires goign to AVR.

I have not uploaded the Project Files yet, as I am still tinkering with the code, but if you want to get the AVR Studio Project Files and the Circuit/Simulation, just say so in the comments…

Published by

Zaid Pirwani

Co-Founder and Design Engineer at EjaadTech + MS Student (Applied Power and Control) + Graduate Teaching Fellow at PAF KIET + Teaching C/C++ at PAF KIET + Industrial Electronics Engineer from IIEE-PCSIR + all round Computer/Electronics Geek