Possibly bug or just tradition?

[hyonlim]

Describe the bug
See above link. It is trying to swap x,y. Not z.

https://github.com/PX4/Firmware/blob/83e532d3399720b9bf10c2ed68adacd9ab4591a0/src/drivers/imu/mpu9250/mpu9250.cpp#L741

What is the purpose of this?

If you see another code, the intention of axes swapping is to make default sensor orientation (sensor on the PCB top, pin 1 toward west direction) to NED.
https://github.com/ArduPilot/ardupilot/blob/2a3676003aadf9fe3b2475b72e9687d77379e099/libraries/AP_InertialSensor/AP_InertialSensor_Invensense.cpp#L424

This code is trying to make ENU (Invensense sensor default axis orientation) to NED (PX4 default axis)

Is this a bug or tradition? Because this makes unnecessary rotation happened during sensor acquisition. What do you think?

[mcsauder]

Hello @hyonlim , this was intentional due to legacy, see comments above the line you linked. the discussion in #9459 sheds a little bit of light:

X and Y were rotated 90, hence the Y negation. Z axis remained with the same orientation. Hopefully this helps clarify. Good work combing through the code with an eye for possible errors!