DSHOT and RPM Filter

calendar Jul 13, 2026 · 3 min read · fpv betaflight dshot rpm-filter bidirectional noise filtering  ·
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DSHOT is a digital ESC protocol. When used bidirectionally, it feeds motor RPM back to the flight controller, enabling the RPM filter — the single biggest improvement to motor noise rejection in modern Betaflight tunes. For the byte-level view of how the frames and eRPM telemetry are encoded on the wire, see DSHOT on the Wire.

DSHOT Variants

ProtocolSpeedNotes
DSHOT150150 kbpsLegacy; slow; not recommended
DSHOT300300 kbpsDefault; compatible with most ESCs
DSHOT600600 kbpsFaster updates; required for some 8K loops
DSHOT12001200 kbpsRarely used; few ESCs support it

DSHOT300 is the default and works on every modern ESC. Use DSHOT600 only if running 8K/8K or the ESC supports it explicitly.

Bidirectional DSHOT

Bidirectional DSHOT adds a return signal from ESC to FC — each ESC sends its motor RPM back at the same time as it receives throttle commands.

Enable in CLI:

1set dshot_bidir = ON
2set motor_pwm_protocol = DSHOT300
3save

After enabling, go to Motors tab in Configurator — each motor should show live RPM readout when spun by hand (props off). If any motor shows 0 RPM, check that the ESC firmware supports bidirectional DSHOT (BLHeli_32 ≥ 32.7, or AM32 with bidir support).

RPM Filter

The RPM filter uses real-time motor RPM telemetry to place notch filters exactly on motor noise harmonics. This eliminates the need for wide-band lowpass filters that add phase delay.

Enable:

1set rpm_filter_harmonics = 3
2set rpm_filter_q = 500
3save

The filter automatically tracks the fundamental motor frequency and its harmonics (2× and 3× typically). As RPM changes during flight, the notch positions move with it.

Effect on tune:

  • Significantly reduces motor noise in the gyro signal
  • Allows higher P/D gains without oscillation
  • Enables lower static notch filter burden (dynamic notch can be reduced)
  • Makes the tune more consistent across throttle ranges

RPM Filter and Betaflight Version

  • BF 4.1+: RPM filter available and stable
  • BF 4.2+: Improved tracking; multi-harmonic support
  • BF 4.3+: Works alongside Dynamic Notch v2 (wider, smarter notch)

Do not run RPM filter on BF versions below 4.1.

Dynamic Notch Filter (Companion)

Even with RPM filter, the dynamic notch filter handles non-motor noise (frame resonance, prop wash, bearing noise). Leave it on:

1set dyn_notch_count = 4
2set dyn_notch_q = 250
3set dyn_notch_min_hz = 100
4set dyn_notch_max_hz = 600
5save

With RPM filter handling motor harmonics, the dynamic notch can be set conservatively (fewer notches, wider Q) to avoid excessive phase delay.

Lowpass Filters

With RPM filter enabled, you can reduce lowpass filter aggression:

1# Gyro lowpass — more permissive with RPM filter
2set gyro_lowpass_hz = 0           # disable static lowpass (RPM filter handles it)
3set gyro_lowpass2_hz = 0
4
5# D-term lowpass — keep this for D-noise
6set dterm_lowpass_hz = 100
7set dterm_lowpass2_hz = 200

The Betaflight cinematic and freestyle presets set these automatically when you apply them.

Troubleshooting

SymptomCause
RPM shown as 0 in Motors tabESC doesn't support bidir DSHOT; bidir not enabled; wrong protocol
Oscillations worse after enablingRPM filter Q too high; harmonics too many
ESC beeps oddly after enablingSome ESCs need reflash to enable bidir mode

Check ESC firmware changelog for bidirectional DSHOT support before assuming hardware failure.

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