I've been working on setting up a new gimbal on an ArduCopter/Orange-Cube quad-copter.
I'm using the Extended controller, and encoders.
I've discovered that the controller always initializes it's heading as "north" and does not update to the frames attitude-heading after that.
If I startup the gimbal when I have it and the copter facing "north" - the gimbal controller heading stays correct. Any other heading at startup will produce errors in commanding the gimbal to point to a lat/long.
I've tested this by using the "point camera here" function in Mission Planner.
I've posted a query about this on the Ardupilot forum - but it seems prudent to bring it up here in case someone knows a solution.