I spent a not so successful morning out on the field trying to get my copter to fly.
With the latest emlid raspbian image, I used apt-get update/upgrade to get the latest compass fixes. No joy, no second compass present.
Downloaded the latest apm.deb with wget and now it has a second compass.
2nd compass set to external and roll 180°, all goes well.
Heading out to the field, powering up the copter, GNSS fix with 15sats, great!
Wait a moment, the compass is off 180° now, what´s that?
Setting the 2nd compass to pitch 180°, recalibrating, everything fine with the compass again.
AHRS_Orientation is set to 4 (yaw 180°) for my copter and as far as I know, the external compass must be set relative to the AHRS_Orientation, but in this case I had to add the AHRS_Orientation to the compass orientation myself. I hope it is clear what I am trying to say.
Another reboot, compass is working and… no GNSS fix…
Tinkering with the GNSS settings, I was able to get a more or less stable fix with 12 sats max, but the copter icon was moving around the map all the time. My Mini Skyhunter with a pixfalcon and a M8N GNSS has a fix with up to 19 sats in the same spot.
First flight, stabilize mode worked, but was undertuned and sluggish. Tried althold mode and it was constantly rising and falling. I changed throttle hover to 0.46 because the copter was hovering with a little less than half throttle. (This method worked with my overpowered pixhawk copter).
Althold was suddenly really agressive, but not able to hold an altitude.
I thought I had done something wrong, had a look at the arducopter wiki and I am pretty sure, they describe the procedure for throttle hover setting the wrong way around. Have a look if you like:
http://ardupilot.org/copter/docs/basic-tuning.html#throttle-tuning
Next I wanted to tune the PIDs to get it to fly more stable, but all the boxes were greyed out in mission planner (except for a few I never really needed before) and even the slider for roll/pitch sensitivity was not present.
I just had enough then and went home.