AHRS errors with limited GPS (no bug)

ArduPlane
1

Has anyone had weird pre-arm messages when testing in-doors with limited GPS?

Scenario -

  • 6X Pro with Arduplane V4.6.0,
  • 2 x M9N GPS units, one unit nearer the window has a good 3D fix, the other does not.
  • I have EK3_ENABLE set to 1 and AHRS_EKF_TYPE to 3

Pre-arm warning: “prearm warning AHRS: not using configured AHRS type”

Plus, the attitude in the HUD is moving around a few degrees in pitch roll and heading. Not good.

Then we went outside, and the HUD went rock solid and the warning disappeared. But we had not, of course, changed the AHRS config.

Pretty sure this is a bug? Is there somewhere I should report a bug other than here?

2

This is a repeatable error/bug: “prearm warning AHRS: not using configured AHRS type” when no GPS fix is presetn. Can anyone tell me how/where to report bug? Thanks!

3

That’s no bug, EKF doesn’t work without global origin set.

4

Hi @LupusTheCanine - thanks and in that case, the message “prearm warning AHRS: not using configured AHRS type” is incorrect, or maybe at least misleading? I’m not sure.

In any case, is there a way I can set a global origin without GPS fix?

5

It is correct, until EKF initializes Ardupilot is running DCM, which is backup AHRS. Since it is configured to use EKF it won’t arm.