Receiver Baud Negotiation

CRSFv3

Sequence:

• On boot, the receiver should start at the standard baud (416666 / 420000).
• Receiver sends request to change baud rate
  • type CRSF_FRAMETYPE_COMMAND (extended)
  • dest CRSF_ADDRESS_FLIGHT_CONTROLLER
  • src CRSF_ADDRESS_CRSF_RECEIVER
  • Command realm CRSF_COMMAND_SUBCMD_GENERAL
  • Subcommand CRSF_COMMAND_SUBCMD_GENERAL_CRSF_SPEED_REQUEST
  • command data
• Flight Controller determines if the baud rate is suitable and sends reply
  • type CRSF_FRAMETYPE_COMMAND (extended)
  • dest CRSF_ADDRESS_CRSF_RECEIVER
  • src CRSF_ADDRESS_FLIGHT_CONTROLLER
  • Command realm CRSF_COMMAND_SUBCMD_GENERAL
  • Subcommand CRSF_COMMAND_SUBCMD_GENERAL_CRSF_SPEED_RESPONSE
  • response command data
• If baud rate was not suitable, Flight Controller ends process here
• Flight controller must not change baud or send any telemetry for 4ms
• Flight controller adjusts baud rate to requested value
• Resume normal operation

NOTE: In CRSFv3 mode, the flight controller must always send heartbeat packets even if telemetry is disabled.

BetaFlight Supported Bauds: 9.6K, 19.2K, 38.4K, 57.6K, 115.2K, 230.4K, 250K, 400K, 460.8K, 500K, 921.6K, 1M, 1.5M, 2M, 2.47M (K=1000, M=1000000). Note that 416666/420K is not supported for baud negotiation after initial connection.