Ah, after some testing, it looks like these both refer to the same IMU, DeviceUsage=3 is for the accelerometer and DeviceUsage=9 is for the gyroscope. The seria

Ah, after some testing, it looks like these both refer to the same IMU, DeviceUsage=3 is for the accelerometer and DeviceUsage=9 is for the gyroscope. The serial number is also the same for both.