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PX4 FAQ

Using an ELRS Receiver with PX4 Firmware

ELRS receivers use the CRSF protocol. To use an ELRS receiver with the open-source PX4-Autopilot firmware, complete the hardware connection and parameter configuration described below.

1. Connect the Flight Controller and Receiver

  • An ELRS receiver normally requires four wires: GND, 5V, Tx, and Rx. Connect the corresponding pads or connector on the receiver to the flight controller's RC port.

Notes

    1. Cross-connect Tx and Rx between the flight controller and receiver.
    1. Insert and remove connectors vertically to avoid bending the contacts. If the wires are soldered, verify that every joint is secure and insulate the connections with heat-shrink tubing to prevent short circuits.
    1. Some receiver manuals label Tx and Rx from the perspective of the connected device, so the markings may appear reversed. If the receiver is not detected, try swapping Tx and Rx.

2. Bind the Radio Transmitter and Receiver

  • Follow the instructions supplied with the transmitter and receiver to bind them. After a successful connection, the receiver indicator remains solid and the transmitter displays the receiver's returned signal strength.

3. Configure PX4 Parameters

  • Search for RC_INPUT_PROTO on the PX4 Parameters page and set it to CRSF.

  • Clear the parameter search. Under the Serial parameter group, set RC_PORT_CONFIG to Radio Controller. Set all other RC_XXX_PRT_CFG parameters (XXX represents the individual protocol) to Disabled. Even when CRSF is used, RC_CRSF_PRT_CFG must be set to Disabled; otherwise, the radio signal cannot be detected. Match the parameters outlined in red in the following image. Parameter availability varies by firmware version, so parameters that are not present can be ignored.

4. Calibrate the Radio

  • Restart the flight controller after changing the parameters.

  • Open the Radio page and move the sticks and switches. The corresponding values in the Channel Monitor should change with each control input.

  • Click Calibrate and follow the on-screen instructions.

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