MotionFX output stuck at zero on STM32L476 Discovery

[HakamYoussef]

Hi everyone,

I am struggling to get MotionFX (9-axis sensor fusion) working on an STM32L476G-DISCOVERY board using the onboard LSM303C (Acc/Mag) and L3GD20 (Gyro).

The Problem: Despite the library being initialized and updated in the main loop, all outputs (data_out.rotation, quaternion) remain strictly at 0.0.

Current Status & Observations:

• Hardware CRC: Enabled and verified. The CRC->DR register changes value constantly, proving that MotionFX_update is processing data.

• Timing: The loop is running at 100Hz. I've tested with both a calculated dt and a fixed dt = 0.01f, but the output remains zero.

• Input Data (data_in):

  • Acc: ~1.0g on Z-axis when flat (normalized to g).

  • Gyro: Normalized to dps (values around 0-5 dps at rest).

  • Mag: Values around -500 µT (normalized using 0.58f LSB for 16G scale).

• Memory: mfx_buffer is 2450 bytes and aligned to 32-bit (uint32_t array).

• Configuration: * mfx_knobs.output_type = MFX_ENGINE_OUTPUT_NED;

  • Library enabled in both 6X and 9X modes.

[Saket_Om]

Hello @HakamYoussef 

I suggest to you to give a look at the source code of the "DataLogFusion" example to see how to use MotionFX library. 

You can refer also to the UM2220