I've been mentioning a desire to do this for a few weeks now, but I now have a prototype up and running.
I'm working on an approach to individually addressable RGB LEDs. There are a couple of similar projects out there:
MPH/JEC's current project - Based on what I have read, depends too much on nodes sourced from an unnamed Asian manufacturer who refuses to even document the protocol used (they had to reverse engineer it!)
MPH/JEC's last project (the pixels) - Each pixel was DMX-aware, this drives cost quite a bit.
Matt Edwards' project at http://doityourselfchristmas.com/for...0250#post80250 - Similar in concept to MPH/JEC's original pixels, but it was AVR-based. Like the original pixels, they were DMX-aware, driving cost up quite a bit. The RS485 receivers I have seen cost nearly as much as my entire parts BOM as it currently stands.
Atmel ATTiny85 AVR - Final design will be a Tiny25.
RGB LED - The unit I currently have is common cathode, final design will be common anode. (My order of 50 units didn't arrive on time, I had to pay $5 for a single unit in a local store today!)
Three current limiting resistors for the LED
One pullup resistor for the Tiny's RST line
Power supply bypass capacitor
The units respond to data sent over I2C. Each unit is sent three bytes at its I2C address - one for each color. I2C means that the nodes do not need any additional interface hardware. (Somewhat similar to MPH/JEC's Asian nodes)
I currently have it prototyped on a breadboard. I only have a single one at the moment, additional units probably won't happen until after the new year (no more RGB LEDs).
Right now I'm driving the I2C bus with a PJRC Teensy loaded with the Micropendous Serial-to-USB firmware:
Eventual goal would be a DMX-to-I2C converter.
I2C only allows 127 nodes per chain, however since a DMX universe could only control around 170-180 nodes (brain is fried after working this all da...), this isn't too much of a limitation.
The firmware is GPL licensed. See the README and comments for known issues with the code. Known issues with the hardware are not documented in this file, but I have mentioned some in subsequent posts. It has been tested on an ATTiny85, but should work without any modifications other than the Makefile and the avrdude programming command in an ATTiny25.
Included is a small Python test script for those who have a USB AVR to play with.
Update: Demo of two nodes on breadboard uploaded to YouTube, see http://doityourselfchristmas.com/for...9&postcount=46
Firmware update released. It is not attached here, all future firmware updates will be in my github repository for this project at http://github.com/Entropy512/I2C_RGB