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Receiver Protocols

Control Protocols

The RF system and the flight-controller receiver protocol are related but not the same thing.

Example:

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ExpressLRS is the radio system.
CRSF is the protocol used between the receiver and Betaflight.
Protocol Typical systems Notes
CRSF ExpressLRS, Crossfire, Tracer Fast serial protocol with control and telemetry
SBUS FrSky, Futaba-style receivers Common older one-way control protocol
F.Port FrSky Combines control and telemetry
IBUS FlySky Simple serial receiver protocol
SRXL2 Spektrum Spektrum serial protocol
PWM old receivers One wire per channel, not common for modern FPV
PPM old receivers Multiple channels on one signal wire, mostly obsolete

CRSF Protocol

Betaflight Setup Pattern

For most serial receivers:

  1. Wire the receiver to a free UART.
  2. Enable Serial RX on that UART.
  3. Select the matching receiver protocol.
  4. Check channel movement in the Receiver tab.
  5. Set failsafe before flying.