Hi julienb
I just sent you a mail, because I started a thread on the monome forum and thought you migh like to join
http://post.monome.org/comments.php?DiscussionID=1549&page=1#Item_15
Right now, I haven't made any significant progress on the arduino side, I was away in Shanghaï (yay!! great city, if you can, you must go there, especially Beijing Dong Lu, a lot of little shops selling everything you need, from ball bearings to electronic components)
I finished the max/msp patch (sends /rgb x y r g b) but now, I'm settling on the key matrix side : how can I have small sized (monome sized, I mean, not sparkfun, a bit too big) backlit pressure sensitive pads? I plan to use RGB leds but I don't yet know if i'm going with smd or through hole components.
xndr on the monome forum mentioned that we could use 2 boards, one for the leds and one for the buttons, and have holes on the top one (buttons matrix) to put the leds through.
For the pressure sensitivity, I wanted to use piezo transducers, but it'll be hard to find ring shaped piezos, so I guess I'll go with pezoresistive fabric (http://www.eeonyx.com/prodte.html). I got an email from Adrian Freed, CNMAT Berkeley, who used it to "bend" sparkfun's & monome buttons pad and add pressure sensitivity.
For the leds, I plan on using 12-channels 12bit PWM chips like Linear LT3595 or TI TLC5940. Still have to order those and understand how they work. Might be a lot easier that trying to deal with MAX7221 and some software kind of PWM.... This would have been a real pain in the a..
As usual, I'll keep you posted ^^