External vs. internal compass (PixHawk v.2.4.6) Help neede with config and compass variance (/inconsistency)

Hi,

happy New Year , one and all :) !

now upgraded from 3DR APM2.5 to a PixHawk FC.

Have 3D (GPS) lock.

The compass calibration is the same as with the ol'good APM, the difference is I see two coordinates rotating and taking the points.

The values obtained are good and in the range written in the WiKi.

Now I'm unsure how to assign the external compass, so the PixHawk uses the external compass in the GPS module?

1- After the calibration success (more than 2000pts) when I move the PixHawk FC, the compass in Mission Planner moves an shows the orientation.

But if I move only the GPS/compass module, (holding the FC still) nothing happens - no movement in MP.

The GPS/compass module config' is compass 1, the internal compass is nr. 2.

I'm wondering what is wrong.

2- Another strange effect is, that with nothing connected to the PixHawk, only linked to the PC via USB, I get a compass variance error (in MP) from the internal FC compass.

I hope somebody could enlighten me what I have to do to correct this compass problem. Thank you :)

Replies

- - - - Cala > Bernardo January 11, 2016 at 3:26pm
        
        If you move higher the gps module? wires are ok? orientation it's ok?
        
        Now when you move the gps module you notice a reaction in M Planner?
- MR60
  
  Hugues > Euan Ramsay January 4, 2016 at 8:07am
  
  That is useful to know however it should not compare the internal vs the external when the internal is disabled!
  - Euan Ramsay > Hugues January 4, 2016 at 8:49am
    
    Agreed!
    - Cala > Euan Ramsay January 4, 2016 at 3:35pm
      
      Be carefull because if you have only one compass enable and compass variance message it's not safe to fly, remember that copter land by default if this err appears; I learned from the worse manner ;)
ANDREA RIVOSECCHI January 4, 2016 at 5:11am

Could be...
MR60

Hugues January 3, 2016 at 10:25pm

Like Euan, I experience the same compass variance message issue independently of the fact one or two compasses are used. Obviously if only one compass is used (the external one) this message on mission planner does not make any sense. I suppose it is a mission planner issue ?
- Euan Ramsay > Hugues January 4, 2016 at 4:20am
  
  Are you still able to fly with this?
  
  Might this be a bug?
Euan Ramsay January 3, 2016 at 9:33pm

I disabled my internal one, successfully re-ran compass calibration (which still uses both compasses btw) and it still gives me orange and red EKF and "compass variance" messages when I move the copter.
Cala January 3, 2016 at 5:00pm

Bernardo: If you move the ext compass and nothing happens and the int works, perhaps you dont disable the correct one or something fails with your ext compass, check plugs and wires, It's a common fail.
- Bernardo > Cala January 4, 2016 at 10:08am
  
  yes, checked. The mx my mz and mx1 my1 mz1 data changes, so the wires should be ok
  
  Will try again.

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External vs. internal compass (PixHawk v.2.4.6) Help neede with config and compass variance (/inconsistency)

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