Inconsistent compasses’ error on Navio 2 AC-3.4rc4

Ok, starting new post on same issue as previously posted.

So, I am getting the “PreArm: Inconsistant Compass Error” after doing the Live Calibration which at the end of the process, there are zero errors for Compass 1 and 2 and 99 errors for Compass 3, which I would expect, as it’s not present.

That said, here is a screenshot of attempting the Onboard Mag Calibration, which does not appear to work.

And the error message on the HUD

Regardless of numerous reboots after the calibration step, as long as there are two compasses selected, the inconsistent compass error message appears. At least that has been my experience. Disable one of the compasses, and using only one compass, either Compass 1 or Compass 2, the error is removed, as there is nothing to be inconsistent with.

What I did find, as a workaround, is to disable Compass 1 and only use Compass 2. No more inconsistent error message.

What is the downside to operating with only one compass?

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Hi Tim,

We have reported the issue with details here:

Unfortunately, Mission Planner does not calibrate second compass correctly. You can see the Inconsistency in calibration results in X, Y and Z between the two compasses. Those values should be approximately similar.

The workaround that we recommend is to use onboard mag calibration. It is strange that is does not work for you. Could you please try a different version of MP?

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I am using MP v1.3.41, and never had the onboard mag calibration, even on previous versions. What I have always done is Live Calibration, and in this setup, disable one of them as noted above.

So, a couple of unanswered question;
1.) What is the risk/downside of using one compass?
2.) If using one compass, is there a preferred compass to use, Compass 1 or Compass 2?
3.) When will rc-7 be baked into the build/image? It released today, 10/26/16. See comments from Randy.

Copter-3.4-rc7 is now available for beta testing. Compared to -rc6 it’s only bug fixes. This may be the final release before the official release if all goes well. The only issue that I’m aware of is some difficulties people are having with compass calibration.



So what happens when you hit “onboard mag calibration”?

  1. Two compasses only add redundancy. There is no real risk in using just one.
  2. If using live calibration, do not use second compass as live calibration does not work for it in MP. You will get wrong calibration on Compass2.
  3. We are going to update everything as soon as 3.4 is released.


When selecting Onboard Mag Calibration nothing happens. Nothing has ever happened when I’ve attempted to use that method, that have always used Live Calibration.

For the time being, will use one compass. Any particular one to use, Compass 1 or Compass 2?

What are your thoughts on the issue?

And I see Randy announced the release of 3.4 today.


3.4 is already available as an update.

Regarding the compass, you should use Compass1 if doing live calibration.

I think that we need to find out why onboard calibration does not work in your case. I put in on the dev issue tracker.

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