Discussions

APM Copter 3.3.2 help with Compass variance

Posted by Michal Paal on February 7, 2016 at 9:43am

Hello,

I'm having a battle with my compasses. I use pixhawk clone and M8N GPS with compass.

I'm unable to find orientation setting, where I will not have EKF compass variance errors.

I think that this is not mag interference problem because this happens when disarmed.

I've disasembled external GPS/compass puck and there are following axis markings:

x axis

z axis O------->

| y axis

My APM configuration is in the attachments, and also example values when facing north.

Do I have faulty compass? or I've tried wrong Orientation settings?

compass1.png

compass2.png

You need to be a member of diydrones to add comments!

Join diydrones

Email me when people reply –

Replies

Arshish Maneckji February 14, 2016 at 2:37am

I had a very similar problem with my M8N & Pixhawk

Here is what I noticed:

1. When indoors and you do not have a GPS FIX and you have the internal compass also enabled you get the compass variance message. Once you get the GPS fix the message goes away.

2. For al practical purposes I always disable the internal compass. I think the general consensus is that its useless. Once you disable it you should stop receiving the compass variance message even when you do not have a GPS fix.
- Michal Paal > Arshish Maneckji February 22, 2016 at 10:56am
  
  Finally the weather and work allowed me to go out. Compass health is much better when GPS is Locked. So i assume this issue is fixed now.
  
  Thank you for tip with disabling internal compass :)
Max Patissier February 7, 2016 at 11:28am

please send pictures of our quadcotper

ps : Boulanger and Patissier, good team !
David Boulanger February 7, 2016 at 10:32am

Michal,

Is your compass mounted upside down?

Regards,

David R. Boulanger
- Michal Paal > David Boulanger February 7, 2016 at 12:32pm
  
  I don't think its upside down. Pixhawk is inside the frame mounted pointing at front, and compass is with arrow forward. The board inside is mounted (as it came from factory) 45 degrees turned (like an diamond) but compass chip has also arrows pointing as I wrote in original post with Y axis backwards and X axis to the right.
  
  IMG_3596.JPG
  
  IMG_3595.JPG
  - David Boulanger > Michal Paal February 7, 2016 at 12:53pm
    
    Well... In the screen shot you posted you had roll set to 180. You may want to change your COMPASS ORIENT Parameter to 0 and see if that helps. I'm not sure why the Y axis arrow is backwards or if it has anything to do with the problem. If it did then when you pointed north it would say south.
    
    Regards,
    
    David R. Boulanger
    - Michal Paal > David Boulanger February 7, 2016 at 1:05pm
      
      Thank you David for such quick responses :)
      
      I've set Compass_orient for compass1 to 0, and raw values from both compasses seem pretty close, but EKF does not aproove.
      
      compass3.png
      
      https://storage.ning.com/topology/rest/1.0/file/get/3702807195?profile=original
      - David Boulanger > Michal Paal February 7, 2016 at 1:22pm
        
        I'm not sure but I noticed you did not have a Gps fix. Is the big square part of the GPS (Antenna) pointing up . I honestly don't know if not having a good GPS fix will cause the variance error to appear. The EKF may require a good fix to prevent the error.
        
        Regards,
        
        David R. Boulanger
        
        P.S. Just trying to help the best I can
        
        Michal Paal > David Boulanger February 7, 2016 at 1:41pm
        
        By the way is there any method how can I find out what is correct compass_orient setting for my compass?
        
        I've tried the hard way - change compass_orient - reboot - calibrate compas - reboot and compare both compass raw values via status page.
        
        Max Patissier > Michal Paal February 7, 2016 at 1:51pm
        
        Usually, there is a small hole in the compass component to mark a direction - it's depend of the manufacturer but if you know the reference, you should be able to find it.