There are some things you have to know before using a FrSky SBUS receiver like the FrSky X4R-SB or FrSky XSR on Airbot’s OMNIBUS flight controllers with F405 MCUs.

Enabling UARTs in Betaflight UI

To enable desired UART ports you may need to take following steps after a putting the newest firmware version onto your board.

  1. Go to the configuration tab and select RX_SERIAL. After this save + reboot. Connect to the board over the same COM port.
  2. Now in the ports tab UART1 (or any other missing UART) should be visible. Select Serial RX for it. Save + Reboot. Reconnect to the board.
  3. Now again, like in step 1, go to the configuration tab and choose RX_SERIAL and SBUS for your receiver. Save + Reboot. Reconnect to the board.

After doing all of the above go to the receiver tab and take a look at stick input from your transmitter.

Telemetry

Since we can’t make use of “set telemetry_inversion = ON” on the OMNIBUS with the F405 MCU, there are 2 options to get telemetry working.

  1. Use external hardware inverter (not so sexy for tight builds).
  2. Solder a wire to your receiver to get inverted signal (see pictures for XSR and X4R-SB).

After soldering the wire connect it to TX pin of UART6 or UART3.

 

X4R-SB
XSR