[NOTE/UPDATE: All the below, from long ago, has been superseded by events. Basic ArduPilot proved capable of every this described here, so we cancelled this version of the product. Thinking about what the next version of ArduPilot could be can be found here. ]
Our main entry-level ArduPilot is designed to be simple, easy to use, and cheap so it just does navigation and leaves stabilization to an stand-alone FMA Co-Pilot with infrared ("thermopile") sensors. But you can tell by our release of our own IR sensor boards the other week, the ultimate aim of this project has been to release a more advanced version that does it all: navigation + stabilization in one. But a standard Arduino isn't powerful enough for all that. So what's the solution?
A dual-core Arduino! So here it is: ArduPilot Pro, with two Arduinos, a MUX/failsafe and built-in GPS onboard. Jordi's design incorporates everything you need for a fully-functioning autopilot, with a target price of under $100, including GPS and thermopile sensors. One ATMega168 processor handles stabilization and the other handles navigation, but because they talk to each other, you get a fully-integrated autopilot, with control over all aircraft channels.
We could have just switched to a much more powerful processor, but that would have cost more, be harder to program and wouldn't benefit from the easy-to-use IDE and the software libraries available for the fantastic open-source Arduino project. The downside of doing it as a dual-core board is that we have to program each Atmega168 processor, as well as the MUX's ATTiny processor, separately, which is why there are three ICSP ports on the board. But in the commercial version, which will come with all processors pre-programmed, there will be little need to fiddle with the stabilization and MUX code, so they can be treated as black-box hardware. (The ICSP ports are just there for anybody who wants to fiddle with them anyway.)