Thanks for your answer, There is no gyroscope difference between NDoF and IMU mode, but there is one with GYROONLY mode. In NDoF and IMU modes, when the gyroscope is close to 0: a little higher or lower, an algorithm modifies the gyroscope data so that it oscillates around 0. In GYROONLY mode, there is no this compensation, it is therefore possible to detect on average the low speeds by having calculated and calibrated in advance the noise of the gyroscope (this noise depend to each USB stick : for two same USB stick, i got 0.06 for the pitch rate of the first and 0.18 for the pitch rate of the second). Do you have any documentation to switch from raw magnetometer to M4G mode magnetometer / angles. On the internet I found a formula where heading is determined with the magnetometer but pitch and roll are determined with the accelerometer. But yet in M4G mode, the pitch and roll seem good (they are not relative). Furthemore it is pitch and roll that I want to use because heading does not seem precise in M4G mode.
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