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FBUS Master

Rotorflight can be the master of a FrSky F.Bus or S.Port bus. The flight controller then polls FrSky sensors connected to it -- voltage, current, GPS, vario, RPM, ESC -- and forwards their readings to your radio with the rest of its telemetry. On F.Bus, it can also drive F.Bus servos.

F.Bus or S.Port?

F.Bus master S.Port master
For Newer FrSky F.Bus devices Older S.Port sensors
Speed 460800 baud 57600 baud
Drives servos Yes -- 16 channels at up to 500 Hz No
UART function F.BUS S.PORT Master

Both can run at once on separate UARTs.

Supported sensors

FLVSS cell voltage, FAS current/voltage, FrSky GPS, VARIO2, RPM and temperature sensors, SBEC, and FrSky ESCs. Up to 32 sensors per bus.

F.Bus master

  1. On the Configuration tab, set a UART to F.BUS. Save and reboot.
  2. Connect the UART's TX pad to the F.Bus signal wire of your sensors and servos. F.Bus is one wire, both ways, and inverted (the default).
  3. Power everything up. The flight controller looks for sensors for the first 5 seconds.

  4. Check in the CLI:

    fbus_sensors

    lists every sensor found, with its physical ID.

  5. Run a sensor discovery on your radio; the new sensors appear.

F.Bus servos

F.Bus servos are bus servos S9-S26, set up in the Bus Servo Configuration table on the Servos tab. Each can follow the mixer (e.g. for the swashplate) or pass a receiver channel straight through. FrSky XACT servos can be programmed over the same wire with the XACT Servo Programming tab.

Settings

Setting Default
fbus_master_frame_rate 500 Hz Servo/channel output rate (25-550).
fbus_master_telemetry_rate 200 Hz Sensor polling rate.
fbus_master_discovery_ms 5000 How long to look for sensors at start-up. Raise it if sensors are missed.
fbus_master_inverted ON Leave on for FrSky hardware.
fbus_master_pinswap OFF Use the RX pin instead of TX.
fbus_master_forwarded_sensors all Up to 8 physical IDs to forward to the radio; 0xFF for unused slots.

S.Port master

  1. Set a UART to S.PORT Master. Save and reboot.
  2. Connect the sensors' S.Port wire. The defaults -- inverted, pin swap on -- suit most FrSky sensors; if nothing is found, toggle sport_master_pinswap.
  3. Check with fbus_sensors, as above.

Troubleshooting

Problem Try
fbus_sensors shows nothing Check the wiring and which pin you used; toggle pin swap.
Sensors found but not on the radio Re-run sensor discovery on the radio. Check telemetry is on, and that fbus_master_forwarded_sensors includes them.
Sensors come and go Raise fbus_master_discovery_ms and lower fbus_master_telemetry_rate.

fbus_sensors clear empties the list and starts discovery again.

To use FrSky sensors as the battery meter, choose FBUS as the voltage or current source on the Power tab.