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

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Introduction to ExpressLRS for Fixed Wings

If you're flying fixed wing planes and want a reliable, low-latency radio link, ExpressLRS (ELRS) is a fantastic choice. It’s an open-source, high-performance RC system popular among hobbyists and makers in the UK and worldwide. This guide will walk you through setting up ExpressLRS for a fixed wing model using PWM outputs, which is common on many flight controllers.

What You’ll Need

  • ExpressLRS compatible transmitter module (TX)
  • ExpressLRS receiver (RX) supporting PWM outputs
  • Flight controller with PWM input pins (or direct servo outputs for fixed wings)
  • USB cable for programming and configuration
  • ExpressLRS Configurator software installed on your PC
  • Basic soldering tools (if wiring is required)

Step 1: Flashing ExpressLRS Firmware

Start by flashing the latest ELRS firmware on both your TX module and RX unit. You can use the ExpressLRS Configurator, a user-friendly tool that guides you through selecting your radio hardware and generating the firmware.

Remember to select the correct hardware target (e.g., "TX Module (ESP32)" for the transmitter or your specific RX model) and your preferred RF settings, such as packet rate (e.g., 50Hz or 500Hz) depending on your flying style.

Step 2: Wiring the Receiver to the Flight Controller

Many fixed wing pilots use flight controllers or standalone receivers that output PWM signals to servos and ESCs. To connect your ELRS receiver to a flight controller expecting PWM inputs, follow these steps:

  • Locate the PWM output pins on your ELRS receiver (usually labelled CH1, CH2, etc.).
  • Connect each PWM channel from the RX to the corresponding PWM input on your flight controller.
  • Ensure that the power (5V) and ground lines are connected properly between the RX and the flight controller.

Some ELRS receivers have built-in PWM outputs; others may require configuring or enabling PWM mode via the ExpressLRS LUA script on your transmitter.

Step 3: Configuring Your Flight Controller

Once wired, configure your flight controller to accept PWM inputs:

  • Access your flight controller’s configuration software (e.g., Betaflight Configurator or INAV Configurator).
  • Set the input protocol to PWM if it isn’t set by default.
  • Assign the correct channels for throttle, aileron, elevator, rudder, and any auxiliary functions.
  • Calibrate your radio inputs to ensure the flight controller responds correctly.

Step 4: Binding and Testing

Bind your ELRS receiver to your transmitter module using the binding procedure outlined in the ELRS documentation:

  • Put the receiver into bind mode (usually by holding a button while powering it up).
  • Use the ELRS Configurator or LUA script on your transmitter to initiate binding.

After binding, test all control surfaces and throttle response to verify the PWM signals are correctly received and translated.

Tips for a Smooth Setup

  • Double-check wiring polarity to avoid damage.
  • Use short and tidy wiring to reduce interference.
  • Keep your firmware updated for the latest stability improvements.
  • Experiment with different packet rates to find what works best for your flying style.

Conclusion

Setting up ExpressLRS on a fixed wing plane with PWM outputs is straightforward and rewarding. With reliable signal quality and low latency, ELRS can significantly enhance your flying experience. Follow these steps, and you’ll be ready to enjoy long-range, crisp control on your next flight!

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