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Compass cal on pixhawk compass strange offsets between compass 1 and 2.

Posted by Francis Chan on December 21, 2015 at 10:30pm

I have an Iris that I've put the GPS on a mast.  Orientation is both facing forward.

  1. After dealing with APM Planner 2.0 hanging up on getting CoA (this really was frustrating...) I ditched AP 2.0 and switched to Mission Planner to upgrade the firmware to the latest (I believe 3.2.1).
  2. I received compass not calibrated so I've spent the past 3 hours trying to "solve" this compass calibration using both AP 2.0 and MP.
  3. Using AP 2.0 live calibration at the end, it tells me that there is discrepancies in the compasses and fails pre-arm... so I tried MP instead.
  4. Using Mission Planner, I do the whole top, bottom, left, right thing several times and get the following values:
    1. Compass 1 (the mast): -4, -6, -29
    2. Compass 2 (pixhawk): 239, -332,-372
  5. I still get compass discrepancy pre-arm failure.

I know with the Iris, the GPS is mounted under the shell upside down facing forward (I think).  Moving it right side up and away from the Pixhawk does that change orientation and therefore I need to change the compass 1 orientation param?

Also what's with the weird pixhawk offsets?  From Randy' youtube video where he gets 19's, 200's seem wrong odd plus with the two compasses disagreeing, I think the pre-arm has the right to fail the arm...

Thanks in advance.

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Replies

  • 3D Robotics
    Chris Anderson December 21, 2015 at 10:33pm

    Best thing is to go to the Full Parameter List tab in MP and reload (and write) the default IRIS parameters from the list on the right. That will eliminate the chance that you had accidentally changed compass orientations in APM Planner. 

    • Francis Chan > Chris Anderson December 22, 2015 at 10:13am

      As an experiment I loaded up the latest APM into another Pixhawk, loaded in the Iris.params, disabled second compass and set compass 1 to internal (since there's no GPS) and ran the compass calibration and got wildly different numbers at:

      • -81, 238, -87
      What values should I be seeing?
      It seems the most "accurate" compass is the one on the mast on my Iris.
    • Francis Chan > Chris Anderson December 22, 2015 at 9:42am

      I loaded in the Iris.params and notated the expected param changes:

      • LOG_BITMASK 26622 to 65535
      • MNT_ANGMAX_TIL 4500 to 0
      • MNT_ANTMIN_TIL -4500 to -9000
      • RC9_REV -1 to 1

      None of them suggest I bumped the orient param, in either case I applied the changes and redid calibration

      Compass 1: -21,-34,-19

      Compass 2: 224,-341,-360

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