Filter tuning: gyro/dterm lowpass, dynamic notch, RPM filter
Filters decide motor heat and latency. The goal: filter just enough to keep noise off the motors — and not one bit more, because every filter costs delay.
The trade-off: noise vs. delay
More filtering removes noise but adds phase lag, which hurts tracking and encourages propwash. Good filter tuning is finding the point where the noise is gone but latency stays minimal.
RPM filter first
With bidirectional DShot, the RPM filter places precise notches on the motor harmonics and removes motor noise at the source. Because it's so targeted, you can then set the lowpass filters higher (faster).
The dynamic notch
The dynamic notch tracks the strongest remaining peaks in the FFT. Count, Q and the frequency range matter — they should cover your actual noise peaks. PIDoctor checks exactly that and suggests dyn_notch values.
Gyro and D-term lowpass
The lowpass filters are the last stage for residual noise. Set them as high as possible without letting noise reach the motors. PIDoctor compares filtered and unfiltered gyro and recommends cutoffs that balance noise against delay.