Connecting ELRS Receiver to Pixhawk 2.4.8 under PX4 Pro - Possible or Not? Need Guidance

PX4 Autopilot
1

Hello,
I wanted to ask some questions about the connections to be made with Pixhawk 2.4.8 (sorry, but I’m new).

I have Pixhawk 2.4.8 and ELRS receiver.
Recently I have successfully paired them following the guide on the ELRS site Elrs guide, but it works only for ardupilot.
So i’m just struggling to find analog of SERIALx_PROTOCOL = 23 (RCIN) and
RSSI_TYPE = 3 settings in PX4

Thanks!

2

ELRS receiver communicate with FMU through CRSF protocol. PX4 does not support this protocol. So, in order to do this you need to include a CRSF to SBUS converter.

3

Short answer, yes it’s possible.
How to do it?
You need to set RC_CRSF_PRT_CFG parameter to the serial that you’re using. BUT You can’t use prebuilt PX4 release (or main) firmware for this, as it depends on PX4 modules crsf_rc. To add RC_CRSF_PRT_CFG to parameter list you need to create your own PX4 build

  1. Get PX4 repo and needed items for build (Follow this guide - Building PX4 Software | PX4 User Guide), i recommend using ubuntu or WSL ubuntu
  2. Build firmware for pixhawk 2.4.8, to do it run “make px4_fmu-v3_default”
  3. Change config by command “make px4_fmu-v3_default boardconfig”.
    a)In the PX4 board config tool, navigate to the drivers submenu, then scroll down to highlight rc_input.
    b) Use the enter key to remove the * from rc_input checkbox.
    c) Scroll to highlight the RC submenu, then press enter to open it.
    d) Scroll to highlight crsf_rc and press enter to enable it.
    e) Save and exit the PX4 board config tool.
  4. Run build again “make px4_fmu-v3_default”
  5. Get your build in “\build” folder and install it to your pixhawk
  6. Set RC_CRSF_PRT_CFG to serail that you are using, in my case Serial 4/5 port

PS: I have connected my receiver to the Serial 4/5 port.
Useful links: Reptile Dragon 2 (RD2) Build | PX4 User Guide