We have some onboard electronics which switch on/off during flight. We know when these systems are activated they cause MAJOR issues with magnetic interference with the onboard (Pixhawk) compass. It is enough to cause a flyaway/crash when in an autonomous/loiter mode. The external compass is far enough away that it is almost entirely immune to this.

Is it possible to disable the internal pixhawk compass?  Basically we would never want to fly unless the external one was operational and if the system fell back to the internal compass it would certainly cause a crash.

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Unfortunately no sense at all :-(

Copter v.3.3.3


Any other ideas?

same here can't disable the internal compass....

Perhaps its not the latest beta update of missionplanner? The compass screen changed considerbly at some point in the last few months.

Very strange !

I disable internal compass with the GUI under compass menu : uncheck compass 2. verifying in the full parameter list that compas use2 = 0. Reboot pixhawk, double check.

Now I move gps 3dr lea 6h virtual horizon is not moving. I move the pixhawk, I have a reaction in virtual horizon. I don't understand how does it works ...

This is because the FC uses the accelerometer/gyro to determine heading change as well as using compass.

The MAG field is subject to variation and if it moves slightly without the FC sensing movement it is ignored, the accelerometer/gyro movement must match the compass reading.

You should notice that if you move the compass 90 deg without the FC moving that you get a Compass Variance warning message in the mission planner HUD.

If you really want to be sure that you FC is using your external compass then boot it up with the compass and FC aligned together and move round until you are pointing north, so you you see it points north in mission planner.

Make a note of what direction north is and disconnect the FC from mission planner and power down.

After its powered down turn the compass so it is at 90 deg to the FC, now reboot the FC and connect to mission planner, you should now see that the north heading in mission planner corresponds to the compass and not the front of the FC .

The proves that the FC has taken north from the external compass.

Not sure if I did the right thing, but in QGC I deleted the third compass ID. I'm getting a message that compass 2 not calibrated, but zero drifting and pointing the right direction too. Arming possible and all flight modes working. 

Happy days :)

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