Bad compass issues

ArduCopter Copter 3.4
1

I just bought a Pixhawk kit from mRobotics, my 2nd one from them. It comes with their Ublox GPS/compass unit as well. I have the Pixhawk and GPS/compass unit taped to a piece of cardboard to maintain their orientations for bench testing.

The compass calibration seems to go okay, although the numbers seem high. I tried both the onboard and live calibrations with similar results.

After the calibration, I’m still getting a lot of “Inconsistent Compasses” and “Compass Variance” errors.

I can load the EKF status window and slowly yaw the system and watch the compass EKF go off the chart relatively quickly.

Any suggestions?

image.jpg2048×1152 580 KB

2

The offsets of your compass are too high.

  • Try Onboard Mag calibration
  • Disable Internal Compass

If this will not solve the problem you might have a problem with the I2C bus .

What is the batch of you Mrobotics Pixhawk (it is written on the PCB ) ?

3

Had this same problem today.
Turning off internal compass completely fixed it.

But is it a good idea to disable them?
I mean aren’t internal compasses designed to be back up?

4

Not really , since internal compass is widely unreliable it often gives readings that are contradictories compared to the one of the external compass .
The point is that if the difference between the two compasses becomes too big , then, EKF do not know which compass is right and so it display an error