Yes another compass thread but this is different

The last couple of weeks I have been trying everything under the sun to make my quad fly in loiter without either spinning into a toilet bowl or starting to move all by itself into various directions. Since there is no way of getting it to not go in a toilet bowl with the internal compasses (I followed the docs to the letter and still get the toilet bowl even when the offsets are green on both or at least on one) and this has been an issue for many of us on 3.4rc1, I tried my last resort, the external 3rd compass.

The setup is as follows:
Navio2 with 3.4rc1
RPi3 with wifi disabled
External HMC5883L compass mounted on a 16cm pole.

I read all the threads pertaining the compass issues we have with the current release, so I think I covered all bases but I am really having trouble understanding why I cannot even get it to work with an external compass.

Here is my setup:

Here is the external compass on my quad:

I ran through the calibration process, have solid offsets there, ran through the compass MOT calibration and got around 30% there, so all good according to Arducopter and with these settings my Pixhawks work flawlessly. Vibe values are low, and the quad flies super stable in stab and alt hold mode. I can literally fly it hands off if there is no wind!
The GPS has a super low HDop (below 1), sat count is well above 9, I mean what else is there???

Short of taking a pixhawk and putting it onto thew same frame, I tried what I know so now I am really stumped. Im also attaching my log from my last test flight.
6.log (1.9 MB)

So please, please, somebody put me out of my misery!

Update: I did swap it for a Pixhawk with the 3dr GPS and compass on a pole, and suprise, similar issues in loiter. So now I was really questioning my sanity but then I decided to take both setups out of our area, drove out onto a wide open field where I did the compass dance and set the compass nr.2 as primary (for the Navio2).

Well what do you know? Finally stable loiter! Of course I still have compass variance errors and the offsets on the 2nd compass are nearing total distance 600 but its a partial success at least.

So clearly something in my area must have been influencing the compass massively - maybe a new radio tower went up since the last time I set up a quad, no idea. But that seems to have been the nr1 issue for me. I will post here if I get the old errors again - if not, consider this the solution.

I will try the 3rd compass too, calibrating it on the same field tomorrow, so lets see what surprises that will bring.

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To get rid of the compass variance error, try to enter the declination for your location in the compass setup screen. The auto declination feature seems to cause the compass variance error.

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Update: There was no way I could get rid of the compass variance, manual declination, on board calib, etc. I now use my external compass only (primary) and disbaled the Navio2 compasses. That works.

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How is the 3DR GPS/compass working for you? Did you follow these setup procedures? Other procedures?

I’m installing one tomorrow…



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I’m curious about the 3DR GPS/compass as well. Over this last weekend I had a bit of a mishap that resulted in a need to replace the GPS puck. Cost is of little concern if use of the 3DR GPS/compass results in a more stable system.

I guess another good question would be, is there any way to make the on-board compasses more stable, or are they just doomed to interference due to the near proximity of the Navio2/RPi? It seems unfortunate that Emlid chose the route of having the compasses built into the FC itself; perhaps the Navio3 will not have this design flaw?

And yes, despite my systems recent troubles, I’m a total fan of Emlid/Navio and can’t wait to see where this project leads :slight_smile:

Mine has been flying smoothly ever since I installed the 3DR GPS/compass…! Get it!!

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It depends on a build. Sometimes external compass would be better, but there are plenty of builds that fly well on internal ones. If you still like to use the external compass, 3DR combo is not the only choice, there are a lot ~10$ boards with HMC5983 chip that could be used.


@mikhail.avkhimenia, now considering the cost of the 3DR GPS/Compass @ $90, what are your thoughts on this Usmile Beitian Ublox NEO-M8N GPS Module? I’m considering it since it carries the same HMC5883L digital compass as the 3DR uBlox GPS with Compass, but at a cost of only $30. I know that often one gets what one pays for, but 1/3 the cost is quite enticing.

And I’m still curious, is there any way to make the on-board compasses more stable, or are they just doomed to interference due to the near proximity of the Navio2/RPi3?

The proximity to high current wiring is what is most important, not RPI or Navio. You do not need to get an external GPS, a single board with compass is sufficient. They go for a few $.

Yup, correct. The GPS from the Navio is just fine. Its the compass you need. I am using arducopter release 3.4 stable btw.

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@igor.vereninov, would the GPS/GNSS antenna MCX not be considered an external compass? I just order a replacement GPS/GNSS antenna MCX since my previous one was lost in a cash over this last weekend. I’m considering the Usmile® Beitian Ublox NEO-M8N since it would cover my need for a GPS as well as an external compass, and as I had mentioned, the Usmile® Beitian Ublox NEO-M8N is 1/3 the cost of the 3DR uBlox GPS with Compass.

Frankly, I’d prefer to minimize the number of masts protruding from my craft as I have a profound appreciation for both form & function :wink:

@jlrogers2 GNSS antenna is not an external compass, it’s just an antenna that connects to the Navios onboard GNSS receiver to allow it to track satellites. Compass is usually a separate chip (in 3DR GPS it’s HMC5883), but on Navio2 we have them bundled with accels and gyros.

If you’d like an external compass and you did order an antenna already you can simply use a board with HMC5883\HMC5983 like this one. It can be connected to the same mast that holds the GNSS antenna (just not on top of the antenna).

The GPS you linked can also be used with some wiring. It won’t be much different from the 3DR GPS (and probably a little bit better since it has a newer chip).

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Right on, thank you for the feed back! :slight_smile: