The Pi Co-op from Dawn Robotics is an easy to use Arduino add-on board for your Pi, on sale here
We've created a video showing what it is, and why you might want to buy one here
Also, we've published a tutorial here
From a slightly more technical viewpoint, we produced the tutorial using an extended version of PyMata
, some Python bindings for Firmata written by Alan Yorinks
. The main change we made to PyMata was to add the ability to make use of the excellent Ino
library if it's installed. This means that if PyMata can't find Firmata when it tries to connect to the Pi Co-op/Arduino, then it will automagically compile and upload the Firmata sketch for you.
Any questions, or constructive comments, much appreciated.