I am working on a project that is going to has two parts, a fixed part and a rotating part. Rather than going into a deep description here you can check out our website that details the project if you need or want to know more.http://www.calvin.edu/academic/engineering/2013-14-team9/index.html
I want to minimize the number of wires that must cross the rotating to fixed break. I plan to use a carefully managed coiled or flexible cable to make this connection. I can't use a typical slip ring because there needs to be a 10.5 inch diameter hole for light to shine through around the center of rotation.
If I can get this cable down to 3 conductors it will make things easier and give me some more options (like coiled headphone cables. There will be an ATMEGA328 on each side of the break that can handle all of the local actions including motor driving and encoder reading, but I need to connect them in some way. If I can get the cable down to 6V, GND, and one signal line that would be ideal.
Does anyone know of an existing library that could connect two Arduinos with only a shared ground and one signal line? I could write my own protocol loosely based on the CAN bus if I had to, but I would love to avoid this if possible. The data rate could be very low(100 bits per second would be sufficient) but it must be bidirectional (Though it will clearly be half-duplex).