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RC Setup

The 305ap supports several RC protocols. Which port and protocol you use depends on your receiver type.

Option A — SBUS / Single-Wire Protocols (RC IN port)​

Port: UART5 (ttyS4), labeled RC IN

UART5 is configured as a single-wire half-duplex port. The signal line is PB13. Connect your receiver's SBUS output directly to this pin.

This port works with:

  • SBUS (e.g. FrSky, Futaba)
  • DSM/DSMX (via spektrum satellite adapter)
  • Single-wire PPM

No QGC configuration is needed. The RC driver activates on this port automatically.

Option B — CRSF / ELRS (Telem 1 port)​

Port: UART4 (ttyS3), labeled Telem 1

CRSF and ELRS require a full-duplex UART. Connect your receiver's TX to the FC's RX (PA1) and the receiver's RX to the FC's TX (PA0).

Configuration in QGroundControl​

  1. Go to Vehicle Setup → Parameters
  2. Set SER_UART4_FUNC = RC Input (13)
  3. Reboot the flight controller
  4. Set RC_INPUT_PROTO = CRSF (5)
  5. Reboot again

The baud rate for CRSF (420000) is set automatically by the RC driver.

ELRS

ExpressLRS receivers use CRSF protocol. The setup is identical to CRSF above.

Option C — CRSF / ELRS (Telem 2 port)​

Port: UART7 (ttyS6), labeled Telem 2

Same procedure as Option B but set SER_UART7_FUNC = RC Input (13) instead.

Verifying RC Input​

In the MAVLink Console (QGC → Analyze Tools → MAVLink Console):

listener input_rc

This prints raw RC channel values. Confirm all channels respond correctly to stick movements.

Flight Mode Assignment​

After RC calibration in QGC, assign a switch to flight modes:

  1. Vehicle Setup → Flight Modes
  2. Assign the mode channel to your desired switch
  3. Configure at least: Stabilized, Position, Return