How to connect the crsf receiver

I use the MATEK F405WING with BL4.1.7 firmware. And I want to connect the ELRS nano recevier.
Then I have some problems , if I use serial 4 to connect the receiver ,which protocol I choose and which baud I use ?

I use the serial 4 to connect the ELRS nano recevicer,and serial4_baud=115, serial4_protocol=23,any other param i would set?

This should generally work. Few more things to know:

  • RC_OPTIONS has a bit 9 “Suppress CRSF mode/rate message for ELRS systems”. You are likely to want to set this bit.
  • Receivers talking CRSF usually want to be set up on a DMA-enabled UART. I don’t remember whether Serial4 has it, but the official Matek documentation recommends Serial1. I believe that ELRS will be fine on either port in fact, but your mileage may vary.

Thank u for your suggestion,I have change the serial4 to serial1,and the param is serial1_baud=115,serial1_options=0,serial1_protocol=23,it still not work :sweat_smile:

  1. Does your receiver actually get power?
  2. Does it connect with the transmitter?
  3. Is the wiring correct? (e.g. the flight controller’s TX must be connected to the receiver’s RX, and vice versa).
  4. Do you power on the transmitter first, then the flight controller? I remember that in most cases if the FC does not see the ELRS receiver that is already connected to the transmitter, it does not initialize the ports properly. This might have changed in recent firmware versions, but it was this way for me in the 4.1.x era.

yes I’m sure the receiver is power on and the transmitter ti connected, and the receiver-TX to serial-RX, receiver-RX to serial-TX. The only different is my receiver is ELRS Micro RX,not LERS nano.

Did you actually flash the correct firmware to this one? It has two variants: the one that outputs PWM, and the one that talks CRSF. The first one will not be able to talk to your controller via a UART, you want the second one.

I ask the seller,he said it will change automatic. thank u very much ,i will change the firmware and try it again.