Gyro¶
The Gyro tab configures gyro signal filtering: removing airframe/motor vibration noise from the gyro signal before it reaches the PID loop, without adding so much delay that the filtering itself starts to hurt tracking.
There are four different tools here, each catching noise a different way. It's tempting to turn all of them up "to be safe," but every filter trades noise removal for delay, and that delay comes straight out of how sharp and locked-in the plane feels -- so the goal is the least filtering that keeps things cool and quiet, not the most.
Which filter should I use?¶
- If you can read real motor RPM (bidirectional DShot, or an RPM/frequency sensor) -- turn on the RPM Filter first. It uses the motor's actual RPM (and any gear ratio) to place notches exactly on the noise it's currently producing, so it introduces far less delay than guessing at a fixed frequency. ESC telemetry alone isn't fast/precise enough for this; it needs bidirectional DShot or a dedicated sensor.
- If you don't have an RPM source -- the Dynamic Notch Filter is the next best option. It watches the gyro signal itself, hunts for noise peaks, and places notches on them automatically. More flexible, but reacts a beat slower than RPM Filter since it has to detect the peak first.
- The Lowpass Filters are the safety net underneath either one -- they don't need to know anything about your setup, they just cut everything above a cutoff. Leave Lowpass 1 on at its default; it's doing useful work even alongside RPM/Dynamic Notch filtering.
- The fixed Notch Filters are for one specific, known resonance you can see in a Blackbox log that the other three aren't already handling -- not a first thing to reach for.
Quick troubleshooting¶
| What you're seeing | Try |
|---|---|
| Servo/motor heat, high-frequency buzzing or growling | Enable RPM Filter or Dynamic Notch; if already on, raise RPM Filter Strength or lower Dynamic Notch Q |
| Mushy, laggy, "flying through jello" | Filtering is too aggressive for the setup -- try a lower RPM Filter Strength, raise Dynamic Notch Q, or raise the Lowpass cutoff |
| Twitchy at a specific throttle/RPM despite otherwise clean filtering | Look for a peak in Blackbox at that condition and target it with a fixed Notch Filter |
RPM Filter¶
Uses the motor's real RPM (and configured gear ratio) to track exactly where vibration is coming from and notch it out, rather than guessing -- this introduces substantially less delay than any filter that has to infer noise from the gyro signal itself. It needs bidirectional DShot or an RPM/frequency sensor; ESC telemetry isn't fast or precise enough. Strength (Low/Medium/High) trades more aggressive noise removal for more delay -- start at Medium and only go higher if you're still seeing heat or noise in Blackbox.
Dynamic Notch Filter¶
Tracks peak noise frequencies in the gyro signal and places notch filters on them automatically -- the best option when there's no RPM source available. Notch Count is 4-6 if this is the only filter running, or 2-4 if it's working alongside an RPM Filter (which is already handling the main, predictable noise). Notch Q controls how narrow/selective each notch is -- 2.0-4.0 is the recommended range; going below 2.0 makes notches much wider and adds significantly more delay. Min/Max Hz should bracket the actual noise band -- Min just below your lowest-RPM noise frequency (but never under 20Hz), Max about 10-20% above the highest noise frequency you expect.
Lowpass Filters¶
Lowpass 1 is the one filter left on by default: a straightforward cutoff that attenuates everything above its frequency, 1st or 2nd order. It can also run in Dynamic mode, sliding its cutoff between a Min and Max frequency instead of sitting fixed, so it can stay tighter at low noise/RPM and open up (less delay) when there's less to filter. Lowpass 2 (expert mode) is a fixed second stage -- generally only needed around 100Hz if RPM Filter or Dynamic Notch is already doing the main work; without either of those, two second-order lowpass stages are the recommended setup.
Notch Filters¶
Two fixed notches for known, specific resonances that aren't already handled by RPM/Dynamic Notch filtering -- each has a Center Frequency (where attenuation is strongest) and a Cutoff Frequency (where the notch starts). For example, a Center of 260Hz with a Cutoff of 160Hz attenuates roughly 160-360Hz, strongest at 260Hz. Find the frequency to target from a Blackbox gyro FFT rather than guessing.