I wanted to report a potential bug I found when using copter 3.4.6.
I recently had an issue with my copter and was able to figure the problem out with the help of folks on this blog (thank you).
When I was trouble shooting my problem I rolled back the firmware to copter 3.3.3. I do not use GPS or Compass, the only modes I need are ALT and LND. when I used 3.3.3 I was able to set ARMING_CHECK: -5 (ignore compass) but that would still display “Bad Compass Health” on the MP HUD. I then set MAG_ENABLE: 0 which removed the warning from the HUD (perfect). everything worked as expected.
When I updated to copter 3.4.6, these settings no longer worked. Any time I tried to arm it says “Arm: Compass not healthy”.
Why would this be the case if ARMING_CHECK is set to -5. So I changed some setting and figured out that the MAG_ENABLE needs to be a value of 1 or 3.4.6 will not arm. This brings the message of “Bad Compass Health” back on the HUD, but because ARMING_CHECK is set to -5 it will arm. Its as if 3.4.6 needs to see that there is a compass installed before it will consider arming even if the arming check has been disabled. Not sure if this has ben reported or there is a good reason for this to happen but I just wanted to report it. If anyone wanted to test this its pretty simple to configure the PixHawk on the bench and see the MP warnings (Note: restart the PixHawk after changing values). I would say that 99% of people will not be effected by this but it was nice being able to remove the “Bad compass health” warning from the MP HUD allowing other issues to be displayed if needed.