How to Set Up ExpressLRS on a Fixed Wing with PWM Outputs

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Introduction

If you're a hobby RC pilot or maker looking to upgrade your fixed-wing aircraft with a reliable and low-latency radio link, ExpressLRS (ELRS) is a fantastic choice. This open-source RC system offers excellent range and responsiveness. In this guide, we'll walk you through setting up ExpressLRS on your fixed wing using PWM outputs – perfect if your flight controller or receiver doesn't support CRSF or serial protocols.

What You’ll Need

Before starting, gather the following components:

  • ExpressLRS-compatible receiver with PWM outputs (e.g., HappyModel EP1, BetaFPV ELRS PWM RX)
  • ExpressLRS transmitter module (compatible with your radio)
  • Fixed wing aircraft with a flight controller or servo connections that accept PWM inputs
  • Appropriate cables and connectors
  • Computer with ExpressLRS Configurator installed
  • Basic soldering tools (if wiring is needed)

Step 1: Flash Your ExpressLRS Receiver

First, you need to flash the receiver firmware matching your hardware and desired frequency band (2.4GHz or 900MHz). Follow these steps:

  • Download and install the ExpressLRS Configurator from the official GitHub repository.
  • Connect your receiver to your PC using a USB interface or a compatible flight controller passthrough.
  • Open the Configurator, select your receiver model and frequency band.
  • Adjust the settings as needed (e.g., power level, failsafe behaviour).
  • Click Build and Flash to install the firmware on your receiver.

Once flashed, disconnect the receiver and prepare for wiring.

Step 2: Wiring the Receiver to Your Fixed Wing

Since you want to use PWM outputs, identify the PWM pins on your receiver. Typically, these are individual servo-style wires, one per channel. Here's how to proceed:

  • Connect each PWM output channel from the receiver to the corresponding input on your flight controller or directly to servos.
  • Ensure the receiver's power and ground wires are connected properly to your aircraft’s power system.
  • Double-check the signal order (usually, channel 1 is aileron, 2 elevator, 3 throttle, 4 rudder).

If your flight controller supports PWM input, connect accordingly. If you’re wiring servos directly, connect the PWM outputs straight to them.

Step 3: Bind the Receiver to Your Transmitter

Binding pairs your transmitter module with the receiver so they communicate exclusively. To do this:

  • Put your transmitter module into bind mode using the ExpressLRS Configurator or the module’s button.
  • Power on your receiver; it should enter bind mode automatically.
  • Wait for the receiver LED to indicate a successful bind (usually a solid or slow blink).
  • Exit bind mode on the transmitter and power cycle your receiver.

Step 4: Test and Calibrate

With everything connected and bound, power up your aircraft on the bench:

  • Move the sticks on your transmitter and verify the servo or control surface movement corresponds correctly.
  • If channels are reversed or mixed up, adjust your flight controller settings or swap wires.
  • Set failsafe positions in the ExpressLRS Configurator to ensure safe behaviour if signal is lost.

Once satisfied, you’re ready for a test flight.

Tips for Success

  • Always double-check wiring polarity and pinouts before powering up.
  • Use quality connectors and keep wiring neat to avoid interference.
  • Keep the firmware updated for best performance and new features.
  • Consider adding a small external antenna to your receiver for better signal quality.

Conclusion

Setting up ExpressLRS with PWM outputs on a fixed wing is straightforward and gives you a robust radio link with excellent range and latency. Whether you’re upgrading an old plane or building from scratch, this system delivers high performance without needing complex serial connections. Happy flying!

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