This calculator can be used to compute cutoff frequency of Butterflight Fast Kalman filter.
Butterflight Fast Kalman filter (FKF) is active when gyro_stage2_filter_type is set to FAST_KALMAN.
Since the filter is looptime dependant, you have to provide Q and R coefficients as well as gyroscope sampling frequency. As a result you will get computed cutoff frequency. Play with Q and R values to get desired filter cutoff value.
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