Purpose

Schema

Led matrix wiring (TOP VIEW).

Preparation

It will use the led matric code that can be found here : Arduino and a Dot Matrix

Setting up the environment

We will use the Arduino without arduino technique with a variation, this time we will use a Atmega 88. Same as 328 but with 8kb memory, plenty sufficient for what we will do. See Arduino without arduino for all the details (Setup the environment and the fuses...)

Code

Everything is here : http://code.google.com/p/alanarduinotools/source/browse/#svn/trunk/LedMatrixCompanion

Standalone mode

Load it with some program that will do some nice display, bouncing ball, random dots, life game ... whatever you can program and find nice.

Display mode

Using the serial pins, pilot it using the super simple protocol to display, image, animated message, again a bouncing ball... Nice thing is that you can chain multiple ones and have a bigger display.
For now protocol doesn't include addressing info, so currently you need as many serial communication pin as module you have. That's job for a Arduino in the background using multiple NewSoftSerial.

Protocol

Very simple, expects the following commands:

• R : clears the display
• CXX : on 3 char, C is the column index (0 <= C <= 7) and XX is the hexadecimal representation of the line (1 = led on, 0 = led off)

Links

Same kind of stuff

• Connected to ethernet and displaying the news http://www.circuitcellar.com/Wiznet/winners/001166.html

Serial on ATmega 88

• The holy graal (works perfectly, nothing to change) : http://jimsmindtank.com/how-to-atmega-usart-in-uart-mode-with-circular-buffers/
• Not working, but some ideas http://tom-itx.dyndns.org:81/~webpage/how_to/atmega168/mega168_rs232_index.php