I have an APM 2.6 set up on a hexacopter but facing backwards. I have the GPS/Compass also facing backward, so both white arrows on the APM and GPS point toward to the rear of the craft. The GPS is the 3DR uBlox. The only way I have been able to calibrate everything correctly was to set the board orientation to YAW 180 as expected, but I had to change the compass orientation from ROLL 180 (external 3DR compass) to PITCH 180. The docs seem to indicated this is incorrect.

My question is, shouldn't this be set to ROLL 180 or did my calibrations correct my backwardness error? My compass offsets all seem reasonable (between +/-50). I have tried this on several recent versions of MP and on ArduCopter 3.01 and 3.1rc2, wiping prom and firmware several times and loading default values.

It seems to work, as I got my first 2 seconds of air time today, but I wonder if this is set correctly or not. Any guidance would be appreciated.

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You cannot put autopilot wrong way. If you have compass wrong way you can still fly but navigation does not work, If you have whole autopilot wrong way it just does not work as it expects that it's facing forward. So best solution is to fix orientation of your autopilot. ArduCopter software supports different orientations only for compass.

 Thanks for the reply. I guess that makes sense.

 What does AHRS_ORIENTATION do?

AHRS Orientation is fully in use on ArduPlane but ArduCopter does not use that yet as we have limited memory on ArduCopter. But yes you are on right track with it. I need to check from Randy that was there any plans to implement it fully on copter software too.

Jani,

The AHRS code is the same on copter, plane and rover. The same AHRS_ORIENTATION parameter works on all 3. They also use the same COMPASS_ORIENT parameter.

Cheers, Tridge

Ok I was not sure about current status on copter. So we are only missing setting tab at Mission Planner as it does not have it other than on advanced list. For Compass orientation we have dropdown menu. We should have dropdown for APM orientation too. 

 So just to clarify, this means that the APM 2.6 can be oriented "backwards" and this will work with the current arduCopter code? Does that mean there is a bug?

 Thanks for your time.

 I think the pull down with options is already under the advanced section in the latest MP.

I put the APM (3.1RC2) up in the air today in the backward orientation and it flew correctly. Does this mean that the compass orientation is not relative to AHRS_ORIENTATION or is PITCH 180 mapped to the wrong value internally?

I'm setting up a new fixed wing model and, due to wiring constraints, need to orient the external GPS with compass with arrow backwards. The APM2.8 is in its normal orientation.  On a previous install, my GPS/compass was oriented with arrows toward the front of the plane, so everything worked will with compass roll  of 180.   But now, I also have a change in Yaw of 180 degrees, yet Mission planner does not have this option, i.e. Roll 180, Yaw 180.  Can anyone help me with this please?



Dieter Preiser said:

I'm setting up a new fixed wing model and, due to wiring constraints, need to orient the external GPS with compass with arrow backwards. The APM2.8 is in its normal orientation.  On a previous install, my GPS/compass was oriented with arrows toward the front of the plane, so everything worked will with compass roll  of 180.   But now, I also have a change in Yaw of 180 degrees, yet Mission planner does not have this option, i.e. Roll 180, Yaw 180.  Can anyone help me with this please?

So after a nice cool bottle of beer and some serious thought and experimentation, I found that I can just change the pitch rotation by 180 degrees to accomplish the same thing.  Problem solved.

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