ExpressLRS 4.0 Released: New Features, Compatibility Changes & What You Should Know Before Upgrading

ExpressLRS 4.0 is finally here. This is a major update with meaningful improvements in performance, flexibility, and reliability—but it also introduces important compatibility changes you need to understand before upgrading. If your current setup is working perfectly, you may not need to upgrade. But if some of the new features and improvements are appealing to you, make sure to backup your config before proceeding.

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Not Compatible with Older Versions

If you install ExpressLRS 4.0, it will NOT work with:

• Devices still running ELRS 3.x, 2.x, or 1.x
• Older STM32-based hardware, including:
  • FrSky R9M modules
  • ImmersionRC Ghost
  • Happymodel PP receivers

You must update both your transmitter (TX) and receiver (RX) to V4 for them to connect. They will not communicate otherwise.

Doesn’t Work with SPI Receivers (Yet?)

Some AIO flight controllers used in whoops have built-in SPI receivers. These are still running ELRS 3.x code and will not work with V4 yet.

Since SPI ELRS firmware is integrated into Betaflight, support depends on a Betaflight update first.

There is no mention in the 4.0 release note that SPI receivers are being abandoned, so I presume it’s only temporary. If you are using SPI receivers, do not update to ExpressLRS 4.0 yet.

What’s New in ExpressLRS 4.0

Get the full release note here: https://github.com/ExpressLRS/ExpressLRS/releases. Here’s a summary.

Choose Your Own Arming Switch

Previously, Channel 5 had to be used for the arm switch.

Now:

• With the alternative arming method, you can assign a specific switch for arming.
• Channel 5 becomes a normal usable channel again.
• Setup is more flexible and convenient.
• Requires EdgeTX 2.11.0 or higher

Better Dynamic Power

ExpressLRS now uses a smarter algorithm for dynamic power.

This means:

• Power adjusts more intelligently.
• Your signal stays strong without constantly blasting maximum output.
• Better battery life on your radio.
• More stable Link Quality (LQ) when using dynamic power.

Automatic Antenna Mode

Before, you had to manually select antenna modes (Gemini, Ant1, Ant2, Switch).

Now, the transmitter and receiver figure it out automatically. No more guessing or manual adjustments—it just works.

What’s Gemini Mode? https://oscarliang.com/expresslrs-gemini/

Full Power DJI Air Unit Without a Flight Controller

This is a big one for fixed wing users who don’t use a flight controller.

It’s known that DJI air units don’t use full power when it doesn’t detect an arm signal (even though when power is set to max). ExpressLRS receivers can now send an arm signal directly to DJI Air Units to trigger full transmission power—no flight controller required.

Faster Telemetry

Telemetry is the data your drone sends back (battery voltage, GPS, signal strength etc).

V4 improvements:

• Telemetry speed is faster.
• Data transfer is more reliable.
• “Sensor Lost” warnings are reduced.

When using Gemini mode, telemetry bandwidth is nearly doubled.

New Web Interface (WebUI)

The configuration webpage has been redesigned:

• Cleaner layout
• Easier to use
• Better organized

Functionality remains similar—just more polished and user-friendly.

Expanded Servo & Output Options (Advanced Users)

For pilots using PWM receivers or special setups:

• Wider servo output range (500–2500µs)
• Expanded failsafe range
• DSHOT 3D support
• More packet modes (especially for LR1121 hardware)

If you don’t know what these are — you probably don’t need them

Lua Script Change

You should also update the ExpressLRS LUA script in your radio.

The lua script is now called: elrs.lua

Delete older versions such as:

• elrsV3.lua
• elrsV3.luac

This prevents duplicate ExpressLRS tools from appearing on your radio.

Important: Settings May Be Wiped When Upgrading

Upgrading to V4 changes the internal filesystem. As a result, changed settings in WebUI may be erased.

You should back up your configuration before updating. To do this, download the hardware.json file from the webUI before updating and then replaced after updating.

Final Thoughts: Should You Update?

ExpressLRS 4.0 is a major update with significant improvements and new features. However, it also breaks compatibility with older firmware versions and certain hardware (such as STM32-based devices, and SPI receivers for now).

Before upgrading:

• Make sure your hardware is supported.
• Back up your current configuration.
• Update both TX and RX together.

If your current setup works perfectly and none of the new features are essential to you, there’s no urgent need to upgrade. Keep flying and avoid hassle. If you decide to update, do it carefully—and make sure everything is compatible first.