APM Up side down relative to the frame

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1

Hello all,

I just set up my quadcopter (APM 2.5) recently and everything was running smoothly before I upgraded it.

Basically, everything is still running properly unless my “roll” in neutral position is -180°.

In fact, my APM is “facing the ground” (between 2 frames plates of course ;p), so that’s where it comes from. Besides, I have an external compass/Gps which is on top of my quad. The gps is facing the sky so the compass is also facing the ground.
==> The angle between my apm and my external compass is null.

In the tutorial to install the external compass, it’s said to select ROTATION_ROLL_180 when calibrating the compass. However I’ve read that this angle is in fact the relative angle between the compass and the apm, so in my case 0°, then I chose ROTATION_NONE.

In order to set the angle between the APM and the frame, I tried to modify the parameter :
AHRS_TRIM_X
which “compensates for the roll angle difference between the control board and the frame”

This value is in radians so I set it to -3,1415 (-180°)

But I got this result :

Anyone knows how to set up parameters and calibration when the APM is upside down ?

I’m interested in any comments / help !

Thanks !!

2

ROTATION_ROLL_180 or just choose “3DR GPS module”.
In the APM, the compass is normally facing upwards, so in the GPS module, it’s facing downwards, hence 180° relative to the APM.

3

Alleluia , I found the right parameter :slight_smile:

It’s called AHRS_ORIENTATION !
copter.ardupilot.com/wiki/arduco … RIENTATION

“Overall board orientation relative to the standard orientation for the board type. This rotates the IMU and compass readings to allow the board to be oriented in your vehicle at any angle. This option takes affect on next boot. After changing you will need to re-level your vehicle.”

My bad, I didn’t find it the first couple of time I searched…

Thx a lot !
I’ll post again in this topic if I have further problem :slight_smile:

4

Cheers kiwa21 :slight_smile:

I am planning a build that might require an upsidedown install :slight_smile: