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BLHeli_S to Bluejay

Small electric helicopters often use BLHeli_S multirotor ESCs. Out of the box, BLHeli_S can't report RPM back to the flight controller, which Rotorflight needs for the governor and the RPM filter. Flashing the ESCs with the open-source Bluejay firmware adds bidirectional DShot, so the RPM comes back on the throttle wire.

Bluejay also lets each ESC have its own settings -- important on an all-in-one board where the main and tail ESCs share one connection -- and can turn off damped light (active braking), which a helicopter without a one-way bearing needs off on the main motor.

Or from the Configurator

In 2.4, the ESC Programming tab can change Bluejay settings directly. Flashing the firmware is still done with ESC Configurator, as below.

Flashing with ESC Configurator

ESC Configurator runs in Chrome or Edge and connects through the flight controller.

  1. Close the Rotorflight Configurator (it holds the USB port).
  2. In ESC Configurator, open Settings and tick Disable common settings, so each ESC can be set separately.
  3. Click Connect, power the ESCs from the flight battery, and click Read Setup.
  4. Click Flash All and choose:
    • Firmware: Bluejay
    • ESC: leave as detected -- it's specific to your hardware
    • Version: the latest
    • PWM frequency: 24 kHz suits most helicopters; very small tail motors (e.g. the K110's) can use higher.
  5. Click Flash. When it's done, click Read Setup again.
  6. Settings:
    • On both ESCs, turn off Brake on stop.
    • On the main motor ESC, set Maximum Braking Strength to 0. This disables damped light, so the rotor freewheels instead of being braked in throttle hold. Leave braking on for the tail motor.
  7. Click Write Setup.

Then in Rotorflight

On the Motors tab:

  • Throttle Protocol: DSHOT300 (or DSHOT600).
  • Dshot RPM Telemetry: on.
  • Main Motor Pole Count: the number of magnets in the motor.

Then check the RPM reads correctly -- see RPM Measurement.