Arduino, Sanguino, Propeller ? – Looking at alternative microcontrollers
The propeller is certainly a capable chip as Dean Goedde is proving this with his Attopilot. The Parallax forums also seem to be quite active and there is a lot of supporting documentation. The downside to the Propeller is that the development boards are quite expensive, especially with the fall of the Australian dollar which has increased costs by 30%.
The Arduino is an open source computing platform which uses a ‘C’ like language called processing. It has a massive user base and the hardware is relatively cheap. The downside to the Arduino is the fact it uses an Atmel 168 microcontroller. This chip has limited memory, only one UART and only has around 25 mips of processing power. The biggest drawback is the single UART and as a minimum for this project I think two are necessary, one for telemetry and one for the GPS.
A software based bit banged additional serial connection is available on the Arduino but it is limited to 9600bps which I doubt will be fast enough. This is possibly where the Sanguino comes in. The Sanguino is an Arduino compatible system that uses the Atmel 644 that features two UARTs. It’s only recently been released and they are still ironing out some issues but it looks promising. The current version which uses a dip mounted chip is huge!
Another possible solution comes from Chris and Jordi at DiyDrones. They have been working for some time on their Ardupilot and Ardupilot Pro systems which are Arduino based autopilots. The standard Ardupilot is a basic autopilot that uses rudder and throttle only and requires an FMA Copilot to provide stabilisation. The Ardupilot Pro also uses IR stabilisation but does the processing itself. The way it handles the required processing power is by having two Arduino chips on the one board one dedicated to stabilisation and the other to navigation. While my project will be different and won’t use the native Ardupilot Pro software, it looks as is if the Ardupilot Pro will provide all the necessary hardware in a small form factor designed which has been designed specifically for fpv/uav development.