My autopilot is the UAV DevBoard from Sparkfun. Mine is the "old" green board which is now superseded by this red board http://www.sparkfun.com/commerce/product_info.php?products_id=9038
I'm posting this in the hope that others will share their experiences of using this board.
It has worked perfectly and I have tested each firmware update as the designer, Bill Premerlani, has released it. It is installed in a Multiplex Twinstar which is powered by two standard Speed 400 motors. The model is quite stable, quite light and flies very slowly, so it doesn't handle wind or turbulence very well.
Although the PitchRollDemo program moved the pitch servos reasonably, at first the AileronCopilot program seemed unresponsive in pitch. I increased the PITCHGAIN from 0.125 to 0.25.
I am now using the AileronCopilot program and after each flight I adjust the control gains. When I have it returning-to-launch-point nicely I will extend the program to fly a route.
My walk around testing of the RTL function was unsatisfactory. The ailerons did something every two seconds and sometimes it was as expected. I thought it was better when I walked faster, so I tried it in the air.
The manual and stabilization modes have been good from the start. In the following video you can see the plane being buffeted by the wind just before I turn the stabilization on at 20 seconds.
At first the RTL mode was taking a very long time to turn the plane, so I reduced the ROLLKP from 0.25, first to 0.1875, then to 0.125 for the video flight. I will reduce it to 0.0625 before the next flight.
This is the 2 minute video of today's flight:-
The camera always points at the plane, so it not clear that the plane is about 300 yards upwind when the RTL mode is selected. The wind's speed is about 50% of the plane's airspeed, so it always ends up downwind after the turn. Most of the time the track corrections were OK, but once or twice I thought the corrections were too small and very slow.