MotionFX quaternion; device stationary; sporadic rotation

[owain-home]

Hi,

I am just starting to use the MotionFX libraries; currently 6DOF, Accel/Mag samples at 100Hz; both propogate and update are being called at that 100Hz rate.

At a rate of 10Hz I spit out the quaternions to a quaternion viewer. All seems to be reasonable other that some of directions of rotations seem to be opposite to what I expect; this might be axes mapping related or even in the viewer; I have not checked. I am running with the library default knobs; library version is V2.8.0 6th March 2023.

The more worrying issue is that with my dev board stationary I occasionally see a sporadic rotation of the device; I have caught this on video; the rotation occurred at approx 8 mins of being stationary.

We are going to check raw sensor and quaternion data to check for any anomalies; but I just wondered if anyone else had seen similar issues?
 

[Federica Bossi]

Hi @owain-home ,

Which is your fw version? Which mode are you using? Mode 3?

Let me know so that I can help you 🙂

[owain-home]

Hi Frederica,

My issue here was overflow of timestamp registers; I had assumed a 32-bit counter; but really it is 24-bit so I had rollover at approx 420s. I have now fixed this in SW.

My current issue is one of axis mapping and interpretation of quaternions and postion (Yaw, roll, pitch).
What are conventions for yaw, pitch and roll.

I see Yaw increasing as device is rotated clockwise. Between 0-360 degrees.
Pitch this seems to go more negative as I tilt board upwards or positive as I tilt downwards +-180 degrees
(I kind of expected positive means nose up; but this seems reversed.
Roll seems to increase as I roll to left and decrease as roll to right.

Is this right or am I sitting facing towards the back of my plane?