Configurature LRS 4.0: What to Know Before You Buy

ExpressLRS 4.0 brings faster telemetry, smarter antenna control, improved dynamic power, and more options for FPV drones and RC aircraft. However, the upgrade also changes firmware compatibility, receiver support, and some channel behavior. Before updating, you need to know whether your transmitter, receiver, and flight controller can work together.

Last checked: October 23, 2026. Dates and figures were verified against official sources.

Is ELRS 4.0 Right for You?

ExpressLRS 4.0 makes the most sense if your existing hardware supports it and you can benefit from its new features. Pilots with reliable ELRS 3.x setups do not need to upgrade simply because a newer major version exists.

ExpressLRS is an open-source radio control link system. It connects a transmitter module, called the TX, to a receiver, called the RX, inside an aircraft or other RC model.

Version 4.0 focuses on improving the quality of that connection and the data sent back to the radio.

Upgrade when the new features solve a real problem, not simply because a newer firmware version is available.

You are a strong candidate for ELRS 4.x if you:

• Use compatible Gemini hardware and want more telemetry bandwidth.
• Want automatic receiver antenna mode selection.
• Use LR1121 hardware and need additional RF packet modes.
• Fly fixed-wing aircraft or use advanced PWM receiver features.
• Want more flexible arming controls with supported EdgeTX firmware.
• Are building a new radio system and prefer the current 4.x firmware family.

You may be better off staying with ELRS 3.x if several existing aircraft use unsupported receivers or upgrading would require expensive hardware replacement.

For a mixed fleet, the cost and effort of updating every receiver may outweigh the performance improvements.

What Breaks Compatibility in ELRS 4.0?

The biggest compatibility change is the radio protocol itself. ExpressLRS 4.x cannot establish a normal control link with transmitters or receivers running ExpressLRS 1.x, 2.x, or 3.x.

This incompatibility is confirmed in the official ExpressLRS 4.0 release notes.

ExpressLRS 4.0.0 was released on February 6, 2026. The update introduced a new over-the-air protocol structure along with changes to supported hardware and configuration storage.

Four compatibility issues deserve attention:

1. Different major firmware versions: A V4 transmitter cannot connect to a V3 receiver, even when the binding phrase matches.
2. Unsupported STM32 devices: The V4 firmware removes support for older ExpressLRS hardware built around affected STM32 targets.
3. SPI receiver firmware: Integrated receivers need flight controller firmware that supports the correct ELRS V4 protocol.
4. Changed configuration storage: Custom settings may disappear during migration because the internal filesystem changes.

There is an important distinction between major and minor versions. Devices in the 4.x family can communicate with one another when their radio hardware, RF modes, and other link settings are compatible.

For example, a supported receiver running 4.0 does not automatically need the identical 4.1 firmware release to communicate with a 4.1 transmitter.

Which TX and RX Must You Update?

Every transmitter and receiver that you want to connect through an ELRS 4.x link must support that firmware family. This includes both internal radio modules and external transmitter modules.

If one receiver remains on ELRS 3.x, it cannot connect to a transmitter running ELRS 4.x. That receiver must be upgraded, replaced, or used with a compatible older transmitter.

Update Both Sides

For a conventional ExpressLRS setup, updating means flashing the transmitter module and the receiver with compatible 4.x firmware.

The two devices do not need identical minor releases, but they must support the same major protocol generation.

1. Identify the exact transmitter module and receiver models.
2. Check that both have supported 4.x firmware targets.
3. Record the current firmware versions and binding configuration.
4. Prepare the correct firmware files for both devices.
5. Update both ends before attempting to use the radio link again.

Keep the radio link out of service while only one end has been upgraded. A transmitter running V4 will not control an aircraft with a V3 receiver.

After flashing, confirm that both devices connect and that stick movement reaches the flight controller.

Unsupported Legacy Hardware

ExpressLRS 4.0 removes support for STM32-based ExpressLRS targets that were available in older firmware generations.

Affected hardware includes:

• Older FrSky R9M transmitter modules running ExpressLRS.
• ImmersionRC Ghost hardware previously supported by ExpressLRS.
• Legacy ExpressLRS PP receiver targets, including affected Happymodel PP hardware.

These devices should not be treated as compatible simply because they work with ELRS 3.x.

Also, do not assume that every older receiver is unsupported. Hardware based on supported ESP platforms may still have valid 4.x firmware targets.

The exact device model and firmware target matter more than the product’s age alone.

What to Check Before Buying ELRS 4.0

Before buying a transmitter or receiver for ExpressLRS 4.x, check its firmware target, radio frequency, receiver type, and supported features. A device advertised simply as ELRS-compatible may ship with older firmware or lack the hardware needed for certain V4 features.

Use the following checks to avoid buying a device that cannot work with your existing radio.

Hardware Compatibility

The ExpressLRS Configurator is the main place to identify supported firmware targets for conventional TX and RX hardware.

The project explains in its hardware selection guidance that supported targets are added after manufacturer collaboration and validation.

Check these details before purchasing:

• Exact product model: Confirm the manufacturer, hardware revision, and firmware target.
• Radio frequency: Make sure the transmitter and receiver support the same band or compatible dual-band operation.
• Receiver connection: Determine whether the receiver uses UART, SPI, PWM, or another supported output arrangement.
• RF chip: Verify whether your hardware uses an LR1121 or another supported radio chipset.
• Antenna configuration: Check whether the receiver has one RF path, antenna diversity, or true Gemini capability.
• Firmware availability: Confirm that a suitable official V4 target exists.

Do not select a generic firmware target for ordinary retail hardware unless the project’s device-specific instructions require it.

When a product is missing from the supported target list, ask the manufacturer for its exact ExpressLRS firmware support details before buying.

Firmware Update Requirements

Most conventional ExpressLRS receivers can be updated through supported methods such as Wi-Fi, USB, or flight controller passthrough. The available method depends on the receiver hardware.

The official receiver updating instructions explain how to choose the device category, firmware target, flashing method, regulatory domain, and binding phrase.

Before you start, confirm that you have:

• A computer with ExpressLRS Configurator or another supported flashing tool.
• The correct firmware target for each device.
• A reliable USB connection or the required Wi-Fi access.
• The binding phrase used by your transmitter and receivers.
• The correct regulatory domain for your location.
• A copy of the existing configuration.

If your aircraft uses an SPI receiver, the process is different. Its receiver code is part of the flight controller firmware, so you cannot update it like a separate UART receiver.

Backup and Migration

Back up the current configuration before upgrading to ExpressLRS 4.0. The firmware changes its internal flash filesystem from SPIFFS to LittleFS, which can erase customized settings.

The most important files are hardware.json and options.json, where applicable.

Also record your receiver settings, including:

• Binding phrase and model matching configuration.
• Serial baud rate and protocol settings.
• Wi-Fi credentials and network preferences.
• Regulatory domain selections.
• Custom hardware pin assignments.
• Packet rate, telemetry, and antenna preferences.

The ExpressLRS 4.0 release notes specify that some PWM mappings and serial protocols are preserved, but you should still check them after flashing.

For Betaflight flight controllers, saving a configuration backup is equally valuable before changing flight controller firmware.

Keep copies of the previous firmware and configuration so you have a practical recovery path if a device needs to return to its earlier setup.

What Do You Gain From ELRS 4.0?

ExpressLRS 4.0 improves telemetry throughput, link synchronization, antenna handling, and transmitter power control. It also introduces features for fixed-wing aircraft, PWM receivers, and compatible DJI Air Unit setups.

The improvements are most noticeable when your hardware supports the specific feature and your existing setup can benefit from it.

Faster and More Reliable Telemetry

Telemetry is the information sent from the aircraft back to the radio. It may include receiver signal quality, battery voltage, GPS information, and flight controller data.

ExpressLRS 4.0 increases telemetry bandwidth in Gemini mode by using both downlink packets for useful data instead of relying on redundant transmission.

The project’s release measurements also show a 30% bandwidth increase for standard telemetry at 500Hz in applicable non-full-resolution modes.

In its example of receiving 14 Betaflight telemetry items, the measured time improves from 6.6 seconds to 5.1 seconds. The combined Gemini improvement reduces the example further to 3.1 seconds.

Faster telemetry delivery can reduce delayed sensor updates. However, an interrupted downlink can still cause telemetry warnings, and improved throughput does not guarantee that all warnings disappear.

Automatic Antenna Selection

ExpressLRS 4.0 can coordinate supported antenna modes between the transmitter and receiver.

For example, a compatible true-diversity receiver can select an appropriate diversity or Gemini arrangement based on the transmitter configuration.

When the receiver cannot use Gemini mode, compatible transmitter setups can fall back to antenna switching.

This reduces manual configuration mistakes when operating aircraft with different receiver capabilities.

Smarter Dynamic Power

Dynamic power allows the transmitter to adjust its output based on radio link conditions.

Version 4.0 introduced statistical power control that estimates the signal quality needed to maintain a strong link.

This can reduce unnecessary high-power operation, although actual battery savings depend on the equipment and flying conditions.

ExpressLRS 4.1.0, released July 17, 2026, further refined this behavior so the transmitter could reduce output power more readily when conditions improved.

The official ExpressLRS 4.1 release notes also confirm compatibility within the 4.x firmware family.

More Flexible Arming and Channels

ExpressLRS 4.0 introduces an alternative arming method that can free Channel 5 for another function.

With EdgeTX 2.11 or newer, supported setups can use a selected switch source to signal arming instead of relying on the traditional CH5 method.

The official radio preparation documentation explains the available arming methods and configuration requirements.

There is also a channel mapping change to understand. In 8-channel and 12-channel full-resolution modes, the firmware now provides exactly the selected number of channels instead of adding an extra channel around CH5.

CH14 carries the arming flag in those modes. Existing channel assignments may need adjustment after upgrading.

Expanded LR1121 Packet Modes

ExpressLRS 4.0 expands the radio modes available on compatible LR1121 hardware.

Examples introduced in the release include:

• K1000 2.4: 1000Hz FSK operation, requiring a suitable module baud rate of at least 921k.
• DK250 2.4: 250Hz redundant FSK operation.
• D50 LoRa 900: 50Hz redundant LoRa operation.
• 25Hz LoRa 900: A lower packet-rate option for compatible 900MHz hardware.

These modes are not universal features of every ELRS receiver or transmitter. They depend on the supported RF hardware.

The newer firmware also brings improved synchronization logic, a redesigned WebUI, and additional receiver output options.

What ELRS 4.0 Still Does Not Support

ExpressLRS 4.0 does not support mixed links with earlier major firmware versions or the legacy STM32 targets removed from the project. It also cannot make unsupported receiver hardware use advanced RF features through software alone.

These limitations matter when upgrading older fleets or building a system from mixed components.

• ELRS 1.x, 2.x, and 3.x links: These cannot communicate directly with an ELRS 4.x link.
• Unsupported STM32 devices: Affected R9M, Ghost, and PP targets cannot be upgraded to the V4 firmware family.
• Unsupported RF modes: A receiver without the necessary hardware cannot use LR1121-specific or Gemini-only features.
• Unsupported antenna arrangements: Single-path receivers do not become true Gemini receivers after a firmware update.
• Older SPI receiver implementations: Flight controller firmware using the V3 protocol cannot communicate with a V4 transmitter.

Can SPI Receivers Work With ELRS 4.0?

Yes, compatible SPI receivers can use the ELRS V4 protocol when their flight controller firmware supports it. This was not available in the same way when ExpressLRS 4.0 first appeared.

The Betaflight 2026.6 release notes confirm ExpressLRS V4 protocol support for SPI receivers.

However, Betaflight keeps ELRS V3 as the default protocol for newly flashed firmware in that release.

To enable ELRS V4, the firmware must be built with the ELRSV4 build flag.

That changes the receiver protocol compatibility. A build configured for V4 cannot connect to an ELRS V3 transmitter.

This is why the original advice that all SPI receivers are unsupported by ExpressLRS 4.0 is no longer correct.

The practical limit is whether your particular flight controller and firmware build support the required protocol.

How to Upgrade to ELRS 4.0 Safely

A safe ExpressLRS 4.0 upgrade starts with identifying compatible targets, saving your settings, and preparing firmware for both sides of the link. Complete the migration before flying again.

These steps apply mainly to conventional ExpressLRS transmitter modules and standalone receivers. Integrated SPI receivers require a different flight controller firmware process.

1. Identify the hardware. Record the exact transmitter and receiver models, including their hardware revisions.
2. Check firmware support. Confirm that each conventional device has a compatible ExpressLRS 4.x firmware target.
3. Back up the settings. Save hardware.json and options.json where available, along with your binding and radio configuration.
4. Choose the firmware release. Select a supported stable 4.x version from the official firmware tools.
5. Configure the firmware. Select the correct device target, regulatory domain, and binding phrase.
6. Flash the receiver. Use its supported update method and wait for successful completion.
7. Flash the transmitter. Update the internal or external TX module before using the radio link again.
8. Update the Lua tool. Install the appropriate elrs.lua script and remove duplicate older ExpressLRS Lua tools if needed.
9. Restore and inspect the settings. Check the saved configuration against the new WebUI options.
10. Test the complete system. Verify binding, stick inputs, auxiliary channels, telemetry, arming, and failsafe operation.

Using Wi-Fi to Update ExpressLRS

Many supported ExpressLRS devices provide their own Wi-Fi hotspot for configuration and firmware updates.

The official Wi-Fi updating guide explains how to enter this mode and upload firmware.

Depending on the device, the network may appear as ExpressLRS TX or ExpressLRS RX.

When connected directly to the device hotspot, the WebUI is commonly available at http://10.0.0.1/.

If the device has previously been configured to join your home Wi-Fi network, its hotspot may not appear. In that case, use the appropriate network access method described in the device documentation.

Choosing the Right Packet Rate

Packet rate controls how often the transmitter sends radio control data. Higher rates generally reduce latency but may trade away receiver sensitivity and usable range.

The official ExpressLRS Lua settings guide provides recommendations for different flying styles.

• General FPV and freestyle: 250Hz or faster is a practical starting point.
• Racing: 500Hz or faster modes may suit pilots prioritizing responsiveness.
• Fixed-wing aircraft: 100Hz Full Resolution is recommended for many setups that need more proportional channels.
• Long-range flying: Choose a supported mode based on receiver sensitivity, antenna setup, RF conditions, and legal power limits.

Do not assume 1000Hz is always better. A lower rate with a stronger link may be more useful than maximum update speed in difficult RF conditions.

If the Transmitter and Receiver Will Not Bind

When devices fail to connect after upgrading, start with firmware compatibility and binding settings before changing hardware.

1. Confirm that the transmitter and receiver both use compatible ELRS 4.x firmware.
2. Check that the transmitter and receiver support the selected RF frequency band and packet mode.
3. Verify that both devices use the intended binding phrase or compatible manual binding method.
4. Confirm that Model Match settings are not preventing the connection.
5. For SPI receivers, verify that the flight controller firmware uses the ELRS V4 protocol.
6. Recheck the firmware target if the device behaves unexpectedly after flashing.

A successful bind should be followed by a receiver input test. Moving the sticks should change the corresponding channels in the flight controller or receiver monitor.

Finally, perform a controlled failsafe test using the manufacturer’s recommended procedure before returning the aircraft to service.

Frequently Asked Questions

Is ELRS Better Than FrSky?

ExpressLRS is often a better choice for pilots who prioritize low latency, long-range capability, and flexible firmware features. However, FrSky systems may still suit users with existing compatible equipment. Actual performance depends on the specific radio protocol, receiver, antennas, and operating conditions.

What Is the Difference Between ELRS and 4-in-1?

ExpressLRS is a dedicated radio control link protocol designed for responsive communication and strong range performance. A 4-in-1 module uses multiple radio chips to support many older RC protocols, including selected FrSky, FlySky, and Spektrum systems. Standard 4-in-1 modules do not replace a dedicated ExpressLRS transmitter.

What Is the Recommended Packet Rate for ELRS?

A 250Hz packet rate is a practical starting point for general FPV flying. Racing pilots may prefer 500Hz or faster, while fixed-wing users may benefit from 100Hz Full Resolution. The best setting depends on the receiver, RF environment, range requirements, and control needs.

What Is the Password for ExpressLRS Wi-Fi?

The default ExpressLRS Wi-Fi hotspot password is expresslrs. Supported transmitters and receivers use this password when creating their own access points unless the configuration has been changed. If the device connects to a saved home network instead, use its configured network settings to access the WebUI.

Can ExpressLRS 4.1 Connect to ExpressLRS 4.0?

Yes, ExpressLRS 4.1 is compatible with devices running supported ExpressLRS 4.x firmware, including 4.0. Both devices must still support compatible radio bands and packet modes. A transmitter using 4.1 cannot connect directly to a receiver that remains on ExpressLRS 3.x.

Does ELRS 4.0 Work With SPI Receivers?

Yes, supported SPI receivers can work with ExpressLRS V4 through compatible flight controller firmware. Betaflight 2026.6 adds V4 protocol support, but V3 remains the default. The ELRSV4 build flag must be enabled for the V4 protocol, and the specific flight controller must support the required firmware build.

Conclusion

ExpressLRS 4.0 offers meaningful improvements in telemetry, antenna control, power management, and advanced receiver features. The main requirement is a compatible transmitter and receiver setup.

Before upgrading, confirm your firmware targets, save your configuration, and account for any SPI receiver or channel mapping changes. If your current ELRS 3.x system works well and the new features are unnecessary, keeping it is a reasonable choice.

For a new build or a compatible existing system, the ExpressLRS 4.x firmware family provides a stronger foundation for future upgrades.

Sources

1. ExpressLRS 4.0 Official Release Notes: Major-version compatibility, removed STM32 support, telemetry improvements, firmware storage changes, and new features.
2. ExpressLRS 4.1 Official Release Notes: Compatibility within the 4.x firmware family and dynamic power improvements.
3. Betaflight 2026.6 Release Notes: SPI receiver ELRS V4 support and the ELRSV4 build flag.
4. ExpressLRS Hardware Selection: Supported firmware targets and hardware validation guidance.
5. ExpressLRS Receiver Updating Guide: Firmware target selection, receiver flashing methods, and configuration requirements.
6. ExpressLRS Radio Preparation: EdgeTX configuration, alternative arming, and channel setup.
7. ExpressLRS Lua Script Guide: Packet rates, telemetry settings, RF modes, and flying-style recommendations.
8. ExpressLRS Wi-Fi Updating Guide: Device hotspots, default Wi-Fi credentials, and firmware updating.

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