80x32 LED matrix display

  
I recently purchased 10 SLM1608 (SLM1606) LED matrix display units from Ebay (you might also contact the seller directly at op16@gmx.de). These are 16x16 LED matrix units with a green and a red LED per pixel allowing each pixel to be switched to either green, red, amber or off. The goal of this LEDMATRIX project was to build a 80x32 pixel display by arranging the displays in two rows with 5 displays each giving a total of 16*16*2*2*5 = 5120 LEDs to be controlled individually. Fortunately these displays come with interated controllers and the data can be shifted into a single display using as few as 6 digital signals. By multiplexing some of the select signals all 10 displays can be controlled with a total of ten wires. Using a cheap ATmega32 microcontroller all ten displays can easily be controlled and updated in real time.
80x32 LED matrix display - schematic

This kind of display is usually controlled via RS232. This has the disadvantage of being very slow and the display data is limited to simple text messages only with the microcontroller of the display doing the actual text drawing. Instead of doing it the same way i decided to use an ethernet interface for the LEDMATRIX display. Even the most simple ethernet interface i am using is fast enough to transfer graphics data in realtime from a PC to the display allowing to update the entire screen 50 times a second. The ethernet support of LEDMATRIX is based on the cirrus logic cs8900 chip which is e.g. supported by the free Procyon AVRlib which has been used for this project. The LEDMATRIX additionally includes a simple speaker allowing to e.g. notify the user of a new message being displayed. Furthermore a TSOP1736 IR receiver can optionally be connected. This device receives and decodes the IR signals used by ordinary TV remote controls. By returning informtion about received IR signals to the controlling PC, the displays contents may e.g. be remotely changed using a simple spare IR remote control. With one display drawing 2A @ 5V, the power supply of the LEDMATRIX needs to source all ten displays and thus needs to be able to provide a total current of 20A. You might be able to find a cheap old PC power supply that delivers 20A on the 5V line. I am using a Lambda UAZ1G 30A power supply. I made some small modifications to...



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