I decided to aggregate some informations in this post, at the beginning to organize my mind, but for the worldwide too.

My way seems to follow these:
JMG website

Devon Djones website

I contacted these two skillful guys, but I guess they are busy for the moment. I completely understand that and but I have to work harder myself.

My parts are:

• 4x Sparkfun Buttons Pads
• 4x Sparkfun PCB
• 64 RGB Leds
• some MAX7221 led drivers ( datasheet here )
• some 74HC164 and 74HC165
• some transistors
• 1x Arduino Diecimila + 1x Wiring board

So, it will be a Arduino based monome clone, I guess (I’ll keep the wiring board for further electronic explorations)

1st, The Software (I mean: firmware)
I thought a lot about that and I think the easier and the more flexible way would be to use the monome firmware published on monome.org ; it works with the monomeserial and it is VERY easy to interface it with Max/Msp or Pure Data etc.
Indeed, this would provide my box to be applications monome-compliant… for further explorations.
There is a firmware altered to make your arduino working like a monome.
It works VERY fine. Of course, as the monome, it works only for one color leds.

The point is: to build a firmware that could work with 3 color data.
Work for driving 64 rgb common cathode leds + work for communicate with monomeserial (protocol has to be respected!)

2nd: The hardware
The big constraint is: each led is common cathode (3 anodes for each colors + a common cathode)
Another constraint: the PCB ; All the cathode on a row are connected. All the anode for one color on a column are connected.
These aren’t BIG constraints, but it forces to be tricky…

The hardware is my main problem.
With the max7221 led driver, no problem for driving 64 leds with just one chip… wow! great.
I could use 3 max, one for each color:
But, as I described, ground (=cathode on the lines) are shared.
For this reason, guys worked to find tips. I found 3 tips I understood. I didn’t test yet, cause my PCBs aren’t completely soldered with leds.

1. http://www.arduino.cc/playground/Main/MultiplexMAX72xx (a timer ISR cyclically power on/off each max… only one works at a time, but Persistence of vision does the job.. only tested with 2 colors and problem for SetRow and SetColumn functions)
2. http://wiring.org.co/cgi-bin/yabb/YaBB.pl?num=1211977580/8#8 (without max, only transistors! I didn’t test, i’m curious about performances)
3. http://wiring.org.co/cgi-bin/yabb/YaBB.pl?num=1211977580/9#9 (transistors to shut lines + max to drive successivemy each color)

I don’t know which is the finest way, performance and reliability speaking.

If you are interested, don’t forget: contact me here: julien.bayle@gmail.com