Firstly a big thanks for all the effort to make the MPU library so smoothly!
Like others, we have an MPU6050 in a different orientation to the default and we have a partial solution by applying rotations to the output. However we have noted that the DMP gets confused, that is it seems to give out inconsistent data and tries to reset itself to what I assume is datum.
In Motion Driver 6.12 – User Guide p9 it describes "The Orientation Matrix" and states that it will "reconfigure the physical hardware sensor axis to the to the device coordinates. A wrong configuration will get you inaccurate results from the sensors data." and also that "The matrixes will be pushed into both the MPL library and DMP for fusion calculations."
What I can't find is any reference to setting those, either in the MPU or the DMP - I'm assuming it might be part of the downloaded code of the DMP in MPU6050_6Axis_MotionApps20.h ( or should we be using the v6.1 version in the Arduino project... but that's a separate question ) I've no idea where to start to find the information as to where that matrix is.
Any hints or ideas welcome!