Compass cal way off

Archive
1

I’m having trouble setting up my external compass/GPS with my Pixhawk. Some data:
Brand new Pixhawk (not sure on the firmware)
3DR external ublox GPS & Compass
Quad ‘V’ pattern
Using a spektrum satellite for RC Rx.
3DR 900MHz telemetry radios
APMplanner 2.0 on Mac

So I’ve watched the videos on the compass dance, tried it at three different locations around town, outdoors and away from buildings and stuff. I keep getting offset values in the hundreds. I think the Z axis was over 500. Sorry I don’t have the exact numbers handy.
As a result, the copter won’t arm. I did change the param to ignore compass for pre-arm check, and have successfully flown just fine. I get full GPS lock. It loiters just fine.

When I review the graphs data, I can see raw mag data for all three axis, and they do vary values as I rotate around. Seems like good data, but the range is 0-1000. If I unstick the external compass and rotate manually, the data does not change. But it I move the Pixhawk, the data does change. This tells me it is not using the external compass. As far as I can find on the net, merely plugging the external compass into the Pixhawk should automatically use the external compass. I’ve tried different settings under initial setup for compass, tried on board PX4, also tried manual roll 180, no differences.

Is this common? Is my compass defective?

2

On Pixhawk you need to set Orientation 0 and the external compass will be automatically detected.

If it is not being detected I would suspect the cable not the unit itself.

3

Thanks Craig! My mind would have gone there eventually but not sure why I had not double checked it earlier. Turns out I had the compass plugged intot he CAN port, not the I2C port. Moved the plug, and got it to calibrate with the highest value around 70.
Thanks for you pointer.