Coduino

The Coduino (Coprocessor for Arduino systems) will be an Arduino-compatible CPU/support on a shield, to enable multiprocessor stacks. It may also be made in multi-CPU version (2 or 4 CPUs on a shield) for really cool projects.

• Will use ATMega328p for compatibility with the Duemilanove board.
• Standard boot loader will be used.
• Serial only in the first revision, no USB-Serial on the board itself (FTDI cables are easy to get now).
• Will communicate with the master Arduino (bottom of the stack) via I2C, leaving all other pins available.
• Main headers will just 'stack-through' the master Arduino, the I/O from the Coduino will be broken out on separate headers (maybe with a 'base board' that can connect to stack shields on the Coduino via a cable?).
• Board could have capability for 1, 2, or 4 (or 3 really, but I like more even numbers) processors, and just get stuffed with the desired number for cost control.
• Local voltage regulation would be best so as to not overload the master's regulator.
  • Power can be pulled from the Vin pin, though this means (if I'm reading the Duemilanove's schematic right) that no power will be received from the master board when using USB power. Will likely want to pull from Vin if there's voltage there, otherwise pull from +5v and bypass the local regulator.
    • Need to test an actual Duemilanove to make sure this is correct.
    • Is it worth doing all this? The Duemilanove's regulator is rated to 800mA, though this would likely be de-rated somewhat due to lack of a heat sink.