Copter yaws in all modes with external mag connected

I have a Pixhawk powered quad here which will slowly yaw clockwise or counterclockwise, depending on the current heading. It seems if the heading is less than 180 degrees, it will yaw anticlockwise, and if it's more than 180 degrees it will yaw clockwise. This happens in stabilize, alt hold etc. I'm running AC 3.1.3, but it happened on 3.1.2 too.

I've tried two different mags, a hmc5883L and a 5893L, and they both produce the same yaw rotation. If I disconnect the external mag, I don't get this rotation.

Has anyone seen this or know what is going on?

I have attached a dataflash log showing the behaviour.


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  • 3D Robotics

    Pixhawk is designed for the 3DR GPS/mag. If you're rolling your own mag, you'll have to change the orientation to match the 3DR one or change the settings in the MP. 

    • I understand that, I had my compass board oriented so that the lettering on the mag chip was oriented in the same direction as the mag mounted onboard the APM 2.5. Surely this would mean that I would run my external mag with rotation set to none?

      I can do some testing with the orientation set differently to see if it changes this behaviour.

      • Sorry I didn't mean that. With the 3DR external mag connected, rotation would be set to roll 180, but I've been running my mag with rotation none, because the orientation of my mag chip is the same as an onboard mag would be. I'm sure i'll get to the bottom of this if it's just a rotation problem though. Cheers

      • 3D Robotics

        No, the external GPS mag is not the same orientation as the mag on APM 2.5. 

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