ExpressLRS is an open-source RC system that has gained popularity due to its affordability, ultra-low latency, and long-range capabilities. However, setting up ExpressLRS can be quite a daunting task for beginners. That’s why in this tutorial, we will guide you through the process of flashing and setting up ExpressLRS 2.4GHz transmitter module and receiver on OpenTX/EdgeTX radio and Betaflight.
New to ExpressLRS? This article explains the advantages of ExpressLRS over other radio control systems and why I prefer to use 2.4GHz than 900MHz.
ExpressLRS 2.4GHz Hardware Selection
All transmitters and receivers with ExpressLRS firmware are compatible regardless the brand.
Radios with Built-in ELRS
Getting a radio with ExpressLRS built-in means you can enjoy this great radio control link without the need for an additional module. It simplifies the setup process and reduces the cost of upgrading your radio system. Some radios with internal modules only go up to 150-250mW, while some may go up to 1W.
|Lite Radio 3||T-Pro||T-Lite V2|
If you have a radio without built-in ExpressLRS, you will need to purchase an ExpressLRS transmitter module in order to use the system. Your radio must have a compatible module bay to install this module to.
Choosing a transmitter module might seem daunting due to the abundance of options available. However, most of them are based on the same open source design by ExpressLRS. The main differences lie in the build quality, features such as screen, maximum output power, and cooling. Opt for one of the reputable brand featured below.
The transmitter module fits into the external JR module bay. Smaller radios might have lite module bay, you will need to get the right size module.
|Full Size Module (JR)|
|Happymodel ESTX24 Pro TX||BetaFPV ELRS Micro TX||Radiomaster Ranger|
Other full size module options:
- Radiomaster Ranger Micro: https://oscarliang.com/product-y4th
- AxisFlying Thor: https://oscarliang.com/product-j7yn
- HGLRC Hermes: https://oscarliang.com/product-jssq
- HiYOUNGER ELRS 2.4GHz: https://oscarliang.com/product-58mr
- Namimno Flash: https://oscarliang.com/product-ie8s
- Happymodel ES24TX: https://oscarliang.com/product-a3r9
|Happymodel ESTX24-Lite TX||Radiomaster Ranger Nano||Jumper AION|
Other Lite module options:
- BetaFPV ELRS Nano TX: https://oscarliang.com/product-c635
- FrSky VANTAC: https://oscarliang.com/product-50wh
- Happymodel ES24TX Slim Pro: https://oscarliang.com/product-xi1z
TX Antenna Upgrades
Stock antennas often have lower gains as they are designed for general use, and their build quality is not always the best. To increase your range, consider upgrading to an aftermarket antenna with better quality and higher gain. With a wide range of sizes and shapes, you can find one that suits your needs and environment.
|HappyModel Moxon (4.2dB)||Namimno Black Pearl Loop (2.8dB)||BetaFPV Moxon (5.6dB)|
|VAS Diamond (2.8dB)||TrueRC True-MOX (2.1dB)||Turbowing Fishbone (7.5dB)|
All ExpressLRS receivers and transmitter modules are cross-compatible, regardless of brand, since they are based on the same open source design. The main differences are build quality, size, and WiFi support for firmware updates and configuration. Lastly, consider the type of antenna that comes with the receiver, as some have a built-in antenna which is more compact, while others come with a U.FL connector for an external antenna which normally provide better range.
When it comes to hardware, consider receivers with “PA” and “LNA” for better range performance. Look for receivers with “TCXO” as they offer a more stable link.
PA (Power Amplifier) and LNA (Low-Noise Amplifier) are components that improve the performance of the receiver. The PA provides a more solid telemetry link for long-range flying, while the LNA significantly increases the sensitivity of the receiver and gives you better range.
TCXO (Temperature Compensated Crystal Oscillator) is a type of oscillator that provides a far more stable frequency with a much wider temperature range. This is important because when components heat up or cool down, it can cause frequency shift in the oscillator, and if that frequency shift is outside of a certain margin, your receiver will lose connection with the transmitter. So, having a receiver with a TCXO will ensure optimal performance and reliability.
|Radiomaster RP1||Radiomaster RP2||x|
|BetaFPV Nano RX||BetaFPV Lite RX||Flywoo EL24E/P RX|
|Happymodel EP1||Happymodel EP2||Happymodel PP|
Diversity offers better range and signal strength. There are two types of diversity receivers. “Antenna Diversity” uses a single radio chip connected to 2 antennas, while “True Diversity” uses 2 independent RF chips, each with its own antenna. True Diversity is more expensive than Antenna Diversity, but makes more effective use of the dual-antenna setups therefore provides better performance. More info on Diversity Receivers.
|BetaFPV SuperD||Radiomaster RP3||x|
|Skystars ELRS Diversity||MATEKSYS ELRS R24 D Diversity||HM EP1 Dual|
|Radiomaster ER5A/ER5C||Matek R24-P||BetaFPV PWM Micro|
Other receiver options:
- HGLRC Hermes: https://s.click.aliexpress.com/e/_DnBCRbn
- JHEMCU RX24T (has PA/LNA amplifier capable of transmitting telemetry data with 100mW, good for long range): https://oscarliang.com/product-x2xp
- JHEMCU SP24S (almost identical to EP1): https://oscarliang.com/product-srb0
- AxisFlying ELRS Receiver: https://oscarliang.com/product-jaxm
RX Antenna Replacement
- BetaFPV Dipole T Antenna: https://oscarliang.com/product-o5vm
- Radiomaster T Antenna: https://oscarliang.com/product-r4t0
Is It Necessary to Update ExpressLRS Firmware?
You don’t have to but you should.
With each update, the open-source project provides bug fixes and performance enhancements, ensuring optimal functionality.
ELRS firmware uses a three-part version number system: A.B.C
- A: major version number
- B: minor version number
- C: patch number
All releases with the same major version number are cross-compatible, but not with different major versions. For instance, 2.0 will work with 2.1, 2.2, 2.5 etc, but 2.x firmware won’t bind with 3.x.
If you have OpenTX on your radio, consider flashing EdgeTX. EdgeTX is a newer, more cutting-edge fork of OpenTX with frequent updates and many additional features. Plus, it offers specific benefits for use with ExpressLRS, such as 500Hz gimbal polling. Check out our guide for flashing EdgeTX to your radio.
If want to continue to use OpenTX, make sure you update to 2.3.12 or newer before attempting to flash ELRS firmware to your transmitter module (the new versions support CRSFShot which is essential for ELRS to work). Our step-by-step guide for flashing OpenTX can help you get started.
How to check whether you have OpenTX or EdgeTX on the radio? Press the “SYS” button, then press the PAGE button until you are on the last page “VERSION”, and you can see the firmware and version there.
Download ExpressLRS Configurator
ExpressLRS Configurator allows you to build, compile and flash firmware for the receivers and transmitter module.
For Windows, click the link with this name: ExpressLRS-Configurator-Setup-X.X.X.exe
Your computer must be connected to the internet while using the Configurator.
Install LUA Script
A LUA script is a mini program on the radio. The ExpressLRS LUA script allows you to change radio link settings, enter binding mode, enable WiFi etc.
If you have the latest version of EdgeTX installed, it comes with ExpressLRS LUA script and you don’t need to do anything.
You can open it by pressing the SYS button, and select “ExpressLRS”.
If you can’t find it, you can download it in the ExpressLRS Configurator by selecting a release version and target, and the “Download LUA Script” button will appear.
The downloaded file should have “.lua” file extension, put that file in this directory on your radio’s SD card: \SCRIPTS\TOOLS\
Identify Hardware and Firmware Version
There are many manufacturers making receivers and transmitter modules for ExpressLRS. You need to know the brand and model of the hardware in order to flash the correct firmware. Flashing the wrong firmware might brick your device.
The easiest way to check is by going to the WiFi webpage. Here’s how to do it.
Firstly, enable WiFi on your device by going to the ExpressLRS LUA script, select WiFi Connectivity.
Then enable WiFi on the desired device.
For receivers, you can also just wait 60 seconds without turning on your transmitter, and it will go into WiFi mode automatically.
On your laptop, you should see a WiFi network called ExpressLRS TX (or ExpressLRS RX). Connect to this network, the password is expresslrs.
Open the browser, and type 10.0.0.1 in the address bar, it will open up a website which will tell you which firmware target it’s using. You can also check the firmware version here.
If you previously setup the device to join your home WiFi network, then you won’t see this WiFi network. Instead, stay connected to your home WiFi, and enter http://elrs_rx.local/ or http://elrs_tx.local/ in the browser address bar.
Alternatively, for ELRS transmitter modules, you can also find the maker, model and firmware version in the LUA script (at the top and bottom of the page). For receivers, go to “Other Devices” in the LUA script, and click on the receiver, firmware version should be displayed there (only works since V3).
Compile and Flash TX Firmware
You can flash the TX module using one of these methods:
I found WiFi to be the easier and more reliable method, I will demonstrate how to do it here. You can also use USB which I will explain shortly later.
Building ELRS TX Firmware
Before flashing, you need to compile the firmware first using the ExpressLRS Configurator.
Under Releases, choose the latest firmware.
Under Device Target, select the brand, and device. In this example, I have the BetaFPV Micro 1W TX, so the Target Device selections would be:
- Device Category: BetaFPV 2.4 GHz
- Device: BetaFPV 2400 TX Micro 1000mW
Let me explain what some of the settings mean.
Regulatory Domains – depending on where you are, the second option “EU_CE” is for people in the EU, anywhere else please select the first option “ISM”.
Binding Phrase – it’s like the key to your car, be creative and make a unique phrase, so people you fly with don’t accidentally use the same phrase and cause problems. Note that other people CAN control your drone if they use the same binding phrase.
Network => Auto WiFi On Interval: how many seconds it turns on WiFi mode if no radio link is established. Default is 60 but I personally prefer to set it to 20. If the receiver goes into WiFi mode you just need to unplug LiPo and plug in again.
Network => HOME_WIFI: See here for more detail.
The Configurator remembers your choices, so you don’t need to select them again the next time.
Flash TX Firmware via WiFI
Once you are happy with the firmware options, select WiFi under Flashing method.
Click the BUILD button (NOT Build and Flash) to compile the firmware. It can take a few mins depending on your internet speed.
When it’s done, a windows should pop up containing two files, one named “firmware.bin” and the other named after the module type you selected. Note that the two files are identical, just different names. You can use either file to flash your TX module.
Plug in the TX module to your radio module bay and power on radio.
On your radio, setup a new model profile, in Model Setup, under External RF, select CRSF in Mode. If your module is an internal module (i.e. built into the radio), then you need to select CRSF under Internal RF.
Open the LUA script by pressing the SYS button, under Tools, select ExpressLRS.
Select “WiFi Connectivity“.
Select “Enable WiFi” and leave the radio powered on.
Go to your computer’s WiFi, you should find a new network called “ExpressLRS TX Module“. The WiFi password is: expresslrs
Open browser and go to 10.0.0.1
Click “Choose File” and select “firmware.bin” generated from the ExpressLRS Configurator earlier.
Click Update. That’s it!
Flash TX Firmware via UART/USB
You can use the USB port on the TX module to flash firmware.
You might need to install CP210x Driver (Download: https://www.silabs.com/developers/usb-to-uart-bridge-vcp-drivers). I tried standard windows driver as it comes with an installer, version 6.7.6 seems to work fine.
This process will work for almost any ExpressLRS transmit module. On some newer modules, you can just plug in the USB cable and it will flash straight away. However some older modules have dip switches, you need to put them in the right position in order to flash. Consult the manual if you see those switches. For example the BetaFPV Micro TX module has those dip switches.
Plug in the USB cable to the TX module, a new COM port should appear on your computer.
In the ExpressLRS Configurator, under Flashing method, select UART. When you are ready, click the BUILD and FLASH button (not Build). The flashing will take a few minutes.
Connect ELRS Receiver to FC
Here’s the pin-out of the PP, EP1 and EP2 receivers.
Connect TX and RX pins to any spare UART on your flight controller. DO NOT use soft-serial because it’s too slow.
Connect TX to RX, and RX to TX.
Here’s the pinout for the BetaFPV ELRS Nano RX.
Build and Flash RX Firmware
For receivers with WiFi built-in, you can flash firmware via WiFi, just like flashing the TX. But personally I found using Betaflight Passthrough easier for flashing RX, and I will demonstrate it here.
Open ExpressLRS Configurator, select the same firmware version as your TX module and choose the device target based on the brand and receiver type. For example:
- For PP receiver, the Device is: HappyModel PP 2400 RX
- For EP1 and EP2 receivers, the Device is: HappyModel EP 2400 RX
Make sure to set the binding phrase as your TX, your RX will just bind with the TX automatically after flashing firmware. If you don’t set a binding phrase, you can bind it manually as described here.
Flash RX Firmware via Betaflight Passthrough
Before proceeding, make sure to configure Betaflight first as described in this section.
Now connect the USB cable to your quad to power the FC and RX.
In ExpressLRS Configurator, choose the COM port of the FC (if not sure, check the COM port in Betaflight Configurator, but remember to disconnect/close it afterwards).
Hit BUILD & FLASH. It will take a few minutes.
Flash RX Firmware via WiFi
Basically the steps are the same as flashing the TX module via WiFi. Some receivers don’t have WiFi capability, so make sure you check before proceeding.
In the ExpressLRS Configurator, hit the BUILD button to compile the firmware.bin file.
By default, if you power the receiver without turning on the radio, after 60 seconds it will enter WiFi mode (LED will be flashing rapidly to indicate that). The RX’s WiFi signal is fairly weak so place the RX close to the WiFi antenna to your computer.
Connect to the WiFi network “ExpressLRS RX“. The WiFi password is: expresslrs
Go to 10.0.0.1 in your browser, and upload the firmware file.
Flash RX Firmware via UART
In the rare event, if neither of the above methods work, you can try UART flashing as described here.
Flashing RX via FDTI
If for whatever reason you bricked your RX, which could happen if you lost power or connection during flashing, you can bring it back by flashing via FDTI: https://www.expresslrs.org/2.0/quick-start/receivers/hmep2400/#flashing-via-ftdi.
Flashing SPI ExpressLRS Receiver
Some whoop flight controllers have ELRS receiver integrated on the same board, and it normally uses SPI connection instead of an UART connection. A good example would be the Happymodel X12 AIO 5in1 FC in the Mobula7 ELRS Edition.
The good thing is that you don’t need to worry about wiring as the receiver is just part of the flight controller.
But flashing the receiver is a bit tricky. In order to update the RX firmware, you have to flash the latest Betaflight firmware, because ExpressLRS firmware is embedded in the Betaflight firmware for that flight controller. All the build options (such as domain, switch mode etc) are in Betaflight CLI (type “get expresslrs” will list them all).
To check if you have a SPI ELRS receiver, simply go to Betaflight Configurator, Receiver tab, and see if it’s set to SPI RX / ExpressLRS.
Here’s how to bind ELRS receivers to a transmitter. There are two ways.
Binding with Binding Phrase
If you’ve set the Binding Phrase when flashing both TX and RX, you shouldn’t have to do anything, because they just automatically bind when powered on. When binding is successful, the status LED on the receiver should stay solid. You can also set the bind phrase on the receiver using the WiFi interface.
When the receiver first powers up, it looks for the transmitter with the matching binding phrase. Once the connection is established it will get synced up, and another device won’t be able to connect to it.
However if someone else uses the same bind phrase on their radio and has a stronger signal than you, it’s possible your receiver will bind to theirs first, and they can take control of your quad. This would be an extremely rare scenario and even if someone wants to do this on purpose it would be very hard to pull off, still, it’s best if you keep your bind phrase a secret and as unique as possible.
Binding Procedure Without Binding Phrase
If you didn’t set a Binding Phrase, you can manually bind your receiver to the transmitter following these steps:
- Power cycle the receiver 3 times in a row will put it in bind mode (power on receiver, then immediately disconnect power. Repeat again). When the RX is powered on for the third time, the LED will start to double-flash, indicating the RX is in binding mode
- Plug in the ELRS TX module to your radio, and enable External RF and select CRSF protocol in Mode. Execute the ELRS lua script in System Settings, Tools. Select [Bind], the LED on the RX module will become solid if bind successfully
If the receiver doesn’t enter bind mode, chances are you flashed the receiver WITH a binding phrase. Try to flash RX firmware again with binding phrase disabled.
When the receiver and transmitter are bound, you should see a “C” in the top right corner in the LUA script when you power them on. However when they are powered off or not bound, you will get a “–“.
Receiver LED Status Indicator
Monochrome LED meaning:
- Solid LED means bind successfully or connection established
- Double-flash means it’s in bind mode
- Flash slowly means waiting for TX module connection
- Flash fast means it’s in WIFI hotspot mode, you can connect to the RX’s WiFi network to upgrade RX firmware by visiting 10.0.0.1 in your browser (password: expresslrs)
- Triple blink then pause – Model Mismatch (make sure Model Match is either disabled on both TX/RX, or the ID are the same at both ends)
Color RGB LED meaning:
- Rainbow fade effect: Starting up
- Green heartbeat: Web update mode enabled
- Slow blink: Waiting for connection from transmitter
- Red rapid flashing: Radio chip not detected
- Orange double blink then pause: Binding mode enabled
- Orange triple blink then pause: Connected to transmitter, but mismatched model-match configuration
- Solid single color: Connected to a transmitter, color indicates packet rate and mode
Betaflight Setup for ExpressLRS Receiver
To setup ExpressLRS RX’s:
Go to the “Ports” tab in the Betaflight configurator, and enable “Serial RX” for the UART you’ve connected the ELRS receiver to. Press “Save”.
In the Receiver tab, under the “Receiver” Section, select “Serial (via UART)“ as the Receiver Mode, and select “CRSF” in Serial Receiver Provider. Enable “Telemetry”, and click the “Save” button.
Your RX should be working now.
To verify, go back to the “Receiver” tab, you should see response from stick movement. If the channels are in the wrong order, just try a different “Channel Map”.
Check if the end points (1000 or lightly lower / 2000 or lightly higher) and mid points (1500) are correct, see this guide on how to adjust if they aren’t correct.
To make sure Telemetry is working, go to the Telemetry page in the radio, and select the option “Delete all sensors“, then “Discover new sensors”.
Asterisk flashing means telemetry is updating.
In the Modes tab, you MUST set AUX 1 as your arm switch (AUX1 is always a 2-position switch, designed specifically for arming in ExpressLRS).
Display LQ and RSSI in OSD
Further Reading: What are LQ and RSSI?
In a nutshell:
- RSSI – Signal strength, how loud the signal is (value from -130dBm to 0dBm)
- LQ – Link Quality, how well your receiver can understand the signal (value from 100% to 0%)
Both indicators are useful, but if you have to pick one, LQ is probably more important.
To display LQ properly you should use the latest version of Betaflight (4.2 or newer), where they introduced a new RFMD:LQ% format for the LQ OSD element.
- In the Receiver tab, Disable RSSI_ADC, set RSSI Channel to Disable
- In the OSD tab, enable Link Quality and RSSI in dBm
It’s useful to have both measurements. For example:
- High LQ, high RSSI = healthy radio link
- Low LQ, high RSSI = noisy RF environment
- High LQ, low RSSI = If you are very far away, caution is needed as you are approaching the end of range; If the receiver is very close to the transmitter, that can be an indicator of antenna problem
- Low LQ, low RSSI = the end of range, you should turn back as failsafe is likely to happen
Mounting Your Antenna
My recommendation is to mount your RX antenna vertically if possible. You can also mount it horizontally if you only fly short range. See this post for more detail.
Digital RC protocols typically contains a failsafe flag in the data packet that the flight controller can detect automatically, so there’s no need for manual setup on the radio. However, it’s crucial to review the Failsafe tab in Betaflight and determine what action the drone should take in the event of a failsafe.
To ensure failsafe is working properly, conduct a props-off test. Arm the quad, remove all propellers, and turn off the radio. The motors should stop spinning within a couple of seconds. Be prepared to unplug the battery in case of any issues.
ELRS LUA Script Settings
There are 3 main settings you should know in ExpressLRS Lua script: Packet Rate), Telem Ratio (telemetry ratio) and TX Power.
Most modules support at least 250mW, some are even capable of up to 1W. Tests have shown that 100mW can achieve a range of 33km with stock 2.4GHz gear, which can outperform a 5.8GHz video link. However, higher power consumption can significantly reduce radio battery life, and increase the risk of overheating without proper cooling. Turning on the fan is recommended when using an output power higher than 250mW (set fan threshold to 250mW).
By enabling the option Dynamic Power, it allows the system to automatically adjust output power based on signal strength. Dynamic Power uses SNR (signal to noise ratio) instead of RSSI to determine power as RSSI doesn’t factor in the noise floor or if the receiver has an amplifier. This can potentially save battery life as it will lower the power when the receiver is close by, it only increases power when it’s needed. If you have Dynamic Power on, MAX Power will be the upper limit.
The appropriate power level for your FPV drone depends on the desired packet rate and range. Running ExpressLRS at 50Hz can provide extraordinary range, even at 100mW. However, if you plan to use a higher packet rate, like 500Hz, your range will be significantly reduced, and you may need more output power to maintain the same range. Familiarize yourself with dB and you can perform calculations using receiver sensitivity and output power to determine the range difference between various packet rates and power levels, this will help you make a decision. 250mW should be enough for most people flying within a couple of miles of range even at 500Hz, but of course higher power will give you better signal penetration too, not just range. Regardless the power, if you want the most reliable link or want to fly long range, it’s generally advisable to stick to a lower packet rate such as 50Hz as it offers higher signal sensitivity.
Packet rate is a compromise of range and latency, you just can’t have both. Higher packet rate has lower latency, but less range.
In ELRS V3, the packet rate modes available are:
- 500Hz, 250Hz, 150Hz, 50Hz – This is normal mode, using LoRa modulation which has longer range and better resistance to RF interference
- F1000, F500 – This is F mode, or FLRC, it offers faster modulation and lower latency, but shorter range than the normal mode. It supports 500Hz and 1000Hz. Great for racers. The F1000 mode has the lowest latency. It’s not about “feel”, I doubt most people can even tell the difference between 150Hz and 500Hz, but sending your command even just 1ms faster means you could react 1ms sooner which is crucial when reacting to critical situations like racing and might help you to avoid a crash
- D500, D250 – This is D mode, or DVDA (Deja Vu Diversity Aid), provides better link connection in complex interference environment by sending the same data packet multiple times to reduce the chance of data loss. D500 and D250 indicate that the same data packet is sent twice and four times respectively. D mode keeps your LQ high and prevent chance of jitter at the cost of slightly higher latency. Great for racing. It works at the FLRC mode (F1000) therefore range will be less than normal mode
- 333Hz Full, 100Hz Full – up to 16 full resolution (10-bit) channels in 100Hz and 333Hz packet rates
FLRC at 1000Hz is the best mode for racing, since it has the lowest latency. LoRa modes (normal mode) have the best range. Slower update rates have higher latency, but longer range. FLRC D modes have reduced jitter, but higher latency than FLRC F modes. Note that 500Hz or higher update rates are not available in some radios, for example the Tango 2 only supports up to 250Hz.
Telemetry is a feature commonly available in radio links. It allows the receiver to send data back to the radio, such as battery voltage, signal link quality, RSSI, GPS coordinates and so on.
Telemetry is enabled by default in ExpressLRS, it sends radio link related data like RSSI and LQ back to the radio. If you intent to use Telemetry to send info about your drone back to the transmitter, such as battery voltage, you have to enable “Telemetry” feature in Betaflight’s Receive tab.
Telemetry Ratio in ExpressLRS settings is how often telemetry data get sent. A larger number means slower telemetry update, e.g. 1:8 means telemetry data is sent every 8 frames, while 1:128 is every 128 frames (e.g. 1:8 is more frequent update than 1:128).
More frequent telemetry will increase latency to the control link, so you can choose to lower telemetry rate or even disable it entirely in the LUA script if you want more consistent packet rate. But I recommend having telemetry if you fly long range.
If you get “Telemetry lost” warnings while your link quality is still looking good, it could be that your telemetry rate is set too low. Try increasing Telem Ratio one step at a time until the “Telemetry Lost” warning disappears.
ELRS supports up to 12 channels.
The first 4 channels are for your sticks – roll, pitch, throttle and yaw. These channels are 10-bit full resolution and their commands are sent every transmission.
The rest of the 8 channels are AUX channels, typically used for switches on a radio. ExpressLRS has two switch modes: Hybrid and Wide. This determines the resolution of these channels and latency.
The first AUX channel, AUX1 (channel 5) is designed to be used for the arming switch, and it’s always a 2-position channel (when OFF it sends 1000, when ON it sends 2000) regardless switch mode, and is sent over the radio every transmission.
AUX2-8 are designed for general uses, they are 6 or 7-bit, meaning they support 64 or 128-positions respectively. Only one of these channels is sent per transmission, so each one is only sent every 7th transmission.
The Switch Mode setting controls how the channels AUX1-AUX8 (channel 5 to 12) are sent to the receiver (the first 4 main channels are always 10-bit). The options are Hybrid & Wide.
With Hybrid mode, most of your channels will only be 2- or 3-position, this is done to reduce latency.
The “Wide” option makes your channels 64- or 128-position which is more than enough for most things we want to do, and that’s what I recommend to use.
Additional Receiver Settings
There are more settings when you connect to the receiver via WiFi (on the page where you flash RX firmware).
First, power on the receiver and wait until it goes into WiFi hotspot mode. It does it automatically after being powered for 60 seconds by default (LED flashing rapidly when it’s in WiFi mode). Or you can also force the receiver to go into WiFi mode in the radio’s LUA script.
Now, connect to the WiFi network (the WiFi password is: expresslrs). In your browser, go to 10.0.0.1
On this page, scroll down and you will find the additional settings like Model Match. For PWM receivers, you will also have settings like PWM Output and Failsafe Positions for each channel, and the option to invert the channel outputs. These setting are not yet available in the LUA script.
Performance Enhancement Settings
In Betaflight, you should apply the suitable RC_Link preset for the particular packat rate you are using. Failure to do so will result in problems with feedforward.
See my Betaflight Tuning guide for more info.
Adding Home WiFi Network
It makes it much easier to flash firmware when you setup “Home WiFi Network” in ExpressLRS. When you put your ELRS transmitter module or receiver in WiFi mode, it will connect automatically to your home WiFi network, then you would be able to flash firmware on a browser from your computer. Easy!
To set it up, you first need to flash your TX module and RX with “HOME_WIFI_SSID” and “HOME_WIFI_PASSWORD”. These are your home WiFi network name and password. Even if you are already on the latest firmware, you have to re-flash to let your transmitter module and receiver know your network login for this to work.
Once that’s done, you can turn on WiFi mode. You can do this in the LUA script.
Open ExpressLRS Configurator, and it will automatically detect your ELRS device. Click on DNS (elrs_tx.local or elrs_rx.local), or the IP address (192.168.0.XXX), if it doesn’t work just try the other, one of them should work.
This will bring you to the page to upload the firmware, same as flashing using the WiFi method we covered before.
How to Use Model Match
Model Match is a number you can assign to a receiver, this allows you to use a model profile on the radio to only control a particular receiver.
If you normally use one model profile to control all of your models (because they are all using the same type of radio receiver and setup the same way) instead of having individual profile for each model, you probably don’t want to use “model match”. But model match is useful for models the requires trims, for example for planes and wings.
To use model match in ExpressLRS, go to Model Setup on your radio, scroll down to Internal RF (or External RF if you are using an external ELRS module). In Receiver, set it to a unique Model ID (any number between 0 and 63, in this example, I will use 2).
Put your receiver in WiFi mode, go to the webpage configuration, Model, and enable Model Match. Set Model ID to the same number you entered in Model Setup on your radio.
Go to ExpressLRS LUA script, and enable Model Match.
Now your receiver can only talk to this particular model profile with Receiver ID 2. That’s it.
If you have a SPI receiver, or a receiver that doesn’t have WiFi capability, you can set Model ID in CLI. You can’t set the ID by just rebinding while model match is on, so i had to go to betaflight CLI and enter:
to show me its ID and i had to:
set expresslrs_model_id = "your ID number"
Tips for Long Range
- Set the highest legally possible transmit power
- Select a lower update rate, e.g. 50Hz will have better range than 500Hz at the same power
- Choose a true diversity receiver with PA and LNA capability
- Use high-quality antennas on your receiver, preferably half-wave dipole (T-shaped) ones. Avoid using ceramic antenna for long range
- Optimize antennas placement as explained here: https://oscarliang.com/antenna-positioning/
- Get a higher gain antenna for your transmitter
- Consider using 900Mhz instead of 2.4Ghz for ultimate long range. (2.4GHz is still very capable though)
- For more tips on long range check out my tutorial: https://oscarliang.com/long-range-fpv-flying-mini-quad/
Same radio controlling multiple receivers simultaneously
What happens if you power up multiple drones that are all bound to the same radio?
You can control all of these drones at the same time, but telemetry won’t work properly as they all trying to send telemetry back to the radio and they will interfere with each other.
To avoid this from happening, you could use model match (each receiver would require an unique ID and a separate model profile). See “How to Use Model Match” in this guide for instructions how to set it up.
Radio keep saying “Telemetry Lost”
You radio system is bi-directional, your transmitter sends commands to the receiver, while the receiver sends telemetry data back to the transmitter. However the receiver has a much lower transmission power compared to the transmitter (e.g. telemetry power is typically less than 100mW, compared to the maximum transmitter power of 500mW or even up to 1W). When your radio is not receiving telemetry your radio will shout “Telemetry Lost” at you, but you might still have full control.
Sometimes you might get constant “telemetry lost” warning even though you are very close to the model. To fix that you can set Telemetry Ratio to standard, a more frequency telemetry might help.
Lua Script just keep Loading
When your run the ExpressLRS LUA script and “loading…” appears on the screen and nothing else happens, make sure you have enabled Internal RF (or External RF if you are using an external module), and set it to CRSF 400K in the model setup.
“Bad Size Given” Error
V2 and V3 handles partition differently (as they moved towards unified target), so when you flash V3 firmware to your module with V2 firmware, the file size get messed up and you get “Bad Size Given” error.
The fix is to download “repartitioner.bin“, on WiFi page, upload this file instead of firmware file. It’s going to say target mismatch, select flash anyway.
Now flash the V3 firmware again, it should go through this time.
Receiver Update Warning: ”Not enough data uploaded!“
If you try to flash firmware of a different target, and force update, you will get this error “Not enough data uploaded”.
It’s a bug/feature in ELRS 2.5 that prevents target changing. If you still want to go ahead and flash a different target, you first need to revert the RX firmware back to 2.0 (on the original target), then flash the different target you wish.
LUA script only shows “Connecting…”
That’s an indication of the ExpressLRS TX module is not talking to the LUA script
Possible causes of the problem:
- TX Module is installed, or is installed incorrectly (pins in the module bay are not making proper contact or broken)
- Maybe the TX module is in WiFi update mode, restart the radio and try again
- Make sure you have set RF protocol to CRSF
- If you are running OpenTX, make sure the version is not too old (it has to be 2.3.12 or after)
How to Install Cooling Fan on Happymodel TX Module
There is no fan plug for the Happymodel 2.4GHZ TX module, you need to solder it directly. I found 3.3V and GND at this capacitor. Make sure you confirm voltage with a multimeter before connecting to avoid damaging the board.
I am using a 20x20x6mm 5v fan which fits perfectly in their new module cover. The fan can be bought on Amazon (affiliate link): https://amzn.to/3ixZpE0. The fan should act as an exhaust and take the hot air out, not blowing onto the PCB to avoid dust building up inside the module. Current draw is quite low so that shouldn’t be an issue. At 5V, 0.05A.
Inconsistent Packet Rate – CRSFShot Not Working
In the ELRS lua script top bar, there is an indicator (e.g. 0:200) which tells you how many packets per second it’s getting from the radio. You can use it to confirm the consistency of the RC link.
Ideally it should always show a stable number that is the same as the packet rate you select. For example: 0:50, 0:150, 0:250, 0:500.
If it shows an inconsistent number like 0:63, or is stuck at 0:250 at every packet rate you select, then your radio does not have CRSFShot working properly.
The latest official release of OpenTX (2.3.12 or newer) already includes CRSFShot, so double check if your OpenTX version is outdated.
Using ExpressLRS Logo as Model Image
I made a logo you can use as model image in the TX16S/T16. You can learn how to use it here.
Image download: google drive.
Install USB to UART Driver
You might or might not need to install this driver on your PC if you want to update your TX via UART: https://www.silabs.com/developers/usb-to-uart-bridge-vcp-drivers
For Taranis QX7 users, if you are running OpenTX, you’ll need to perform this mod in order to run 400k baud rate on your radio. It’s not needed, but it is recommended if you want to get the most out of ELRS: https://www.youtube.com/watch?v=mHfQe05XJn8&ab_channel=edrone
If you run EdgeTX you won’t need to do this mod as the bug has been addressed in software.
For more detailed explanation of the system, visit ExpressLRS official wiki, I barely scratched the surface here: https://github.com/
- Jun 2021 – Updated guide: OpenTX 2.3.12 has been released, no longer need to flash nightly
- Jul 2021 – Updated: ExpressLRS 1.0 official release
- Aug 2021 – Added info for BetaFPV ELRS Nano TX and RX
- Nov 2021 – Updated product list
- Feb 2022 – Updated the complete TX, RX and antenna options currently available on the market
- May 2022 – Updated instructions for version 2.5, added info about adding home network, updated screenshot of LUA script (V2)
- Oct 2022 – Updated guide for ELRS V3 release, added PWM receiver products
- Mar 2023 – Added info about model match, added more FAQ, updated product links
A Complete Guide to Flashing and Setting Up ExpressLRS
I’m running ELRSConfig1.5.6 Trying to flash some new Radiomaster receivers: Target = Radiomaster RP1/2 2400RX. The build generates firmware for HappyModel_EP_2400RX, which is not the right target. I believe it should build RM_RP_2400RX which is the correct target.
I’ve searched all over with no luck on this problem. Any insight, or places I should search?
Hello Oscar, thanks for the instructions.
It is the best
Buongiorno, ho una TX16S MARCK 2, con Edge Tx 2.8 ELRS 3.1.2, non ho capito quando devo scaricare lo script lua e inserirlo nella scheda sd, se mi funziona tutto regolarmente, quando devo sostituire lo script lua
Hello Oscar, is it possible to mount an ELRS reciever on an AIO board of a Mobula7? can u tell me how???
If there’s a spare uart on the board you should be able to do it. Connection and seutp are the same as a full size flight controller really.
Sir can u please help me…i have new elrs happymodel ep2, and the 2.5.1 firmware version, the problem is i have my remot and 3 other rx is 2.3.0 version, can i downgrade my happymodel ep2 to 2.3.0…how can i do that??? Thx…
Your remote on 2.3 should work with your receiver on 2.5.1, there’s no need to downgrade. See explanation here: https://oscarliang.com/setup-expresslrs-2-4ghz/#Should-I-Update-ExpressLRS-Firmware
When ever I need answers quick, I can count on this site for all of them. Just started with ELRS and couldn’t figure out why I couldn’t upload both files to the receiver, kept saying not enough space after trying to upload the second file. Came here and discovered Configurator creates two identical files with different names, firmware.bin and another .bin with the name of the receiver. Firmware.bin uploaded fine and I didn’t realize that receiver name.bin wasn’t needed. I was pulling my hair out till I came here. Thanks Oscar!
I am having trouble flashing my jumper t18 and my happy model ES24_Pro_series_tx, I had no problem a week or so ago flahing both my radio and modual,I just bought a Flywoo 2S firefly and flashed that with no problem, COM 3,I get a “Failed to connect to ESP32, The last thing it said was com1, and that error,
firmware.bin is 1422k for my HappyModel ES24TX Express LRS TX Module. My Jumper T18 Pro has Open TX 2.3.15 installed. The Lua script is installed and appears to work perfectly. My PC connects to b 10.0.0.1 and the WiFi firmware update commences with the horizontal bar graph showing the percent installed. At the finish I receive a Firmware Update Failed Not Enough Space error. What are my options?
My beta fpv pwm rx i use firmware tx rx of lite rx to fly, signal lost and fall from a distant area about 330 feet how do fix it.
Thank you for this brilliant and comprehensive guide.
Hi Oscar….thanks for sharing lot of tutorial. It’s really help me to learn. Many thanks….success always for you
Great tutorial!! Another reason the Lua script may be stuck “Connecting…”: if you have another Lua script running that interferes with it. I had Yaapu telemetry running and it kept ELRS Lua from connecting.
There is no way in hell I could have set this up without you. Thanks
Hi Oscar, my name is Paul and I’m from Argentina. Thanks to your tutorials I was able to install edge tx on my taranis qx7s. Pass from Frsky R9m to beta 1W elrs. I followed your tutorial and luckily I was able to do everything. Perfect flight, but I constantly have the telemetry lost alarm, telemetry recovery and the screen of the taranis flickers. Never fail safe. The values I have are: 500mhz, 1:128 in the beta module, 400 bauds and onebit option activated in the taranis. Lq and Rssi Db perfect. It makes me suspicious to fly like this and I looked for information but I didn’t find anything. I don’t understand what’s going on and I would appreciate some help.
Thank you very much in advance and I love his videos because they are the clearest thing I have seen so far.
See my reply in the last comment.
Hello Oscar. I love how he explains things.
I followed all your tutorial to the letter and it works perfect on my taranis qx7s. The problem I have is that the alarm sounds constantly telemetry lost, telemetry recovered. Perfect flight and Rssi db and LQ are maintained, but that doesn’t stop sounding.
I use 500mhz and telemetry ratio 1:128, 400baud and onebit option…………thank you and I hope you can solve that.
Did you see the FAQ regarding QX7? https://oscarliang.com/setup-expresslrs-2-4ghz/#taranis-qx7
The easiest fix is to flash EdgeTX: How to Flash EdgeTX to Your OpenTX Radio (TX16S)
Thank you very much…I will try again
i liked the EXPRESSLRS setup
Any ELRS TX Module is plug and play for the FRSKY Taranis QX7 access requiring at most firmware update?
Do any of them require any adaptation or physical modification on the FRSKY Taranis QX7 access?
Hello! My receiver can’t bind with the transmitter. The LED of the receiver is flashing all the time(the period is about 1.3s), and the WIFI of the receiver is always on. I’ve set the same binding code, but they can’t bind automatically. What’s more, the “binding” button on the transmitter is also not working.
And the version of my transmitter is “unknown”, I’m considering if this is the problem.
Try to flash all your hardware to the latest version see if that fixes it?
That includes your TX and RX firmware and EdgeTX
Using zorro elrs. My packet rate is 500. Telem ratio is 1:128. I would constantly get telem lost, telem found while flying. Should it turn it off or lower the ratio?
Try lower it (more frequent telemetry updates).
I have three quads running on ELRS now, but am confused by the LUA on my FrSky X12S Horus. It seems to take forever to run, though it does in the end complete, and the quads bind and run.
Hello Oscar, thank you so much!
Can you tell us how to set to (Radiomaster Tx16S) a telemetry setup warning etc?
Like on what RSSI etc. you should get worried to not failsafe etc….
i have found something like that once for Crossfire but i switch completly to ELRS so that would be great!
Thank you so much for all your work!
I see there is now a HappyModel ELRS PWM receiver module. Any difference in setting that one up?
Did not bind and work for pass through (obviously?) but did work for wireless at VERY close range
Thanks for your info. My TX16S max v2 is on order and I just received my ELRS module. Looking forward to getting it all working and this guide will be invaluable.
Just FYI, the happy model version of the elrs module seems to have a JST plug for a 5v fan on the board – no need to go off the resistors.
Brilliant, clear and concise instructions Oscar. Thanks you!
What is the current draw at 1000mw, 500mw, 250mw, and 100mw? You mentioned that it is only 50ma but at which power level? Thanks!
Hi Oscar, I followed your steps in setting up my Jumper T-Pro TX. When I reached the step on performing a BootLoader on my TX; I could not locate the right buttons on my Jumper T-Pro. Wonder if you could advise. Thanks a million.
if you type in “jumper t-pro bootloader mode” you will find a ton of tutorial on how to do this :)
Can anyone help me out I’ve installed elrs beta fpv 2.4 on my 5 inch with the jbf7 and a succex 45a esc with a tx16s everything works great until I try and do punch outs at full throttle I get rx loss for about a second and then the signal comes back and if I keep the throttle at 100% the signal doesn’t come back and it just falls out of the sky. I’ve tried switching 5v regulators ground wires and tried changing the uart. I’ve got a capacitor on it 1000mf. I have also tried moving the receiver to different places with no luck
If you have a module with ELRS 1.x installed, you need the 1.x version of the LUA script. You can use it to install the latest firmware, then install the v2 LUA script.
hello there… is it possible tu use an elrs rx on silverware lite 2s?
Thanks Oscar, very helpful!
I am having trouble flashing my RX/TX via the Express LRS configurator. When I get to the Build and Flash stage, I get an error message stating that my Mac is using an outdated version of Python (??), that I need to have Python 3 installed. I’ve tried to upgrade Python but have been unsuccessful with my older Mac OS. What should be my next move?
i am not sure as i am not a Mac user, can you use something like Virtual Machine or Wine and run Windows on it?
Will try. Thanks Oscar for the reply.
As always Oscar nice tutorial! but I would love to see how you setup your ELRS telemetry widgets please share a link if you already have done this.
Merci pour ce guide qui m’a été très utile pour flasher mon betafpc micro TX 1000mw ,flashe en 2.2.0
I am running TX16S with 2.3.14. I am unable to get the expresslrs Lua to work. It just shows “connecting” and all question marks. I did find that I am able to use the elrs module if I use the crossfire setup Lua.
For those having similar issues to me give the crossfire Lua a try
For 500hz, in 4.3 feedforward averaging should be set to 2_point, feedforward_smoothing to 65, and jitter reduction of 5.
For 250hz, in 4.3 feedforward averaging should be set to 2_point, feedforward_smoothing to 45, and jitter reduction to 6.
I’m running OpenTX 2.3.14. I installed the Lua Scripts as instructed and as soon as I did, all my models were deleted. When I tried “executing” the Lua, like BS below all I get is a loading screen.
Same here,… how did you pass the step with the infinite loading ?
Had a question ..
When we use two radios and intend to fly a model / quad that has an ELRS receiver installed , is it possible to bind both radios as long as we use two separate ELRS TX modules installed on each radio ?
On the Frsky R-XSR this was possible by using TX cloning method . Is this possible or straightforward for ELRS ?
I’ve had 2.3.14 loaded on my TX16S running FrSky and just got the HappyModel ELRS24 module. Two weird issues. When I select “noheli” in the build options and flash the TX, it will not boot. If I build without that selected the TX will boot. For now leaving that unchecked.
When I go to SYS > TOOLS on the TX and select ExpressLRS all I get is a loading screen and nothing appears. I’ve left it for quite a while and the module is not loading. Any thoughts?
If that’s the same Aio that resides in Tina whoop and c25, you can hook up a hm ep Rx the way you explained/ identically to crossfire.
That is for elrs 1.0.2.
For other brand receivers and other firmwares this might not be possible.
Ideal way is a set of full uarts where no inverted pads or sbus are used on)split off.
So you might need to change wiring so you take the UART that is controlling your VTX now.
i go into tools on my radiomaster tx12 and i only have spektrum there, and i updated my open tx to the newest version what did i do wrong?? please ive been at this for over 4 hours
followed things step by step …. 3 times … I get telemetry just fine, but no response in radio setting in betaflight …enough to drive an old man over the edge … any ideas ??
Hi, have you solved your problem? the same thing happens to me using literadio 2 elrs, binding happens but I have no answer in the betaflight receiver tab.
Did you find any solution to this problem? I have the same issue with EP1 and Literadio 3 ELRS.
Thanks for the great info Oscar, maybe a dumb question but
do you know if this will work with Spektrum transmitters? They use the SRXL2 or CRSF/2 protocols.
For an ELRS RX to work with a Mamba F411 AIO, would I use the SBus+TX1 to TX+RX in the same way the diagrams show a crossfire tying SBus+TX1 to CH2+CH1? The Mamba docs aren’t particularly clear on whether SBus pin can be used as a generic uart RX1 unless I missed something.
If that’s the same Aio that resides in Tina whoop and c25, you can hook up a hm ep Rx the way you explained/ identically to crossfire.
That is for elrs 1.0.2.
For other brand receivers and other firmwares this might not be possible.
Ideal way is a set of full uarts where no inverted pads or sbus are used on)split off.
So you might need to change wiring so you take the UART that is controlling your VTX now.
Tapping voltage that way for the fan seems dubious to me without understanding of the circuitry there. Obviously something is being filtered by the capacitors, and adding a fan may disturb the filtering with the voltage spikes/drops it causes. I can’t see the traces, so I couldn’t figure out out the circuitry works, so I opted to simply not use the fan: that’s probably less risky.
Hello, my EP2 RX blinks the led slowly and doesn’t go into wifi mode. What should I do?
first, it takes 20 seconds to go into wifi mode so make sure your waiting long enough, if its not going in i would try firmware via uart or betaflight passthrough
Hi there,my lua script is showing up instead i am getting “attempt to compare with nil” message.
Anyidea how to solve this?
What betaflight build version is ELRS supported from? Ie how old a betaflight build? The reason I ask is that I build my own betaflight versions.
Talked to HappyModel today. According to their support there is no need for cooling fan when running at the max output, 250mW, for the ES24TX. There is soon coming another version of the ES24TX that is called ES24TX Pro that has built in fan and capable of 1000mW.
Hey! Where could one find that cover with the mount for the fan? Looks 3D printed. Are there STL files anywhere?
Will it work with jumper t8sg plus?
Thank for the rewiew :)
Can you use ES24TX with FRSky XD9+?
Because no can see the module in the XD9+
Yes it should be compatible with Frsky X9D+.
What would be the procedure please for the XD9 + because I have been trying for weeks but I still do not see the module
what do you mean you don’t see the module?
how to enable external module and set it to CRSF and disable internal module? i did everything right but i still have this issue. i’m using frsky taranis x9d+.
Please follow this instruction: https://oscarliang.com/setup-expresslrs-2-4ghz/#:~:text=under%20External%20RF
Two important additions that I ran into during setup:
serialrx_inverted and serialrx_halfduplex need to be OFF
If the elrs receiver LED stays on solid after powerup, without ever turning off, it is stuck in the bootloader, caused by the elrs rx pad being pulled low during boot.
Common reason: F4 boards with an inverter for SBUS on one of the serial ports do this, even if you dont use the inverted pad. Use an entirely different serial port for elrs and it will work.
Shoutout to Alessandro for telling me this because I could not find any help in any of the elrs guides or forums.
Yes I have that exactly same problem on a mamba f411 aio with an jhemcu ep24s receiver.
But it works fine on happymodel ep1.
i have a xilo f4 board how do i know if the pad is inverted or not?
Hi, what do you mean by “serialrx_inverted and serialrx_halfduplex need to be OFF”
Where must I find this option? (yes i’m a noob?)
Is there possibility to use ExpressLRS TX/RX on old PPM radios? Of course with former setting on OpenTX radio/
Hi, thanks for all your work is a great help for everybody.
I’m having trouble with finding sensors with ExpressLRS 2.4? I can only get it to find 10 sensors: (1RSS, 2RSS, RQly, RSNR, ANT, RFMD, TPWR, TRSS, TQly, TSNR) I already tried updating the RX and TX to the latest firmware 1.0.1 with the telemetry option, I also deleted all sensor and discover new sensor, and also increase the Packet Rates but still doesn’t seems to work, any suggestions? could it be that I’m missing to configurate something in betaflight?
thank you Oscar for another page packed with info!!
I have the same issue RODRIGO C has, cant get battery voltage (rxbat i believe) on the sensor list.
using DIY 2.4 ghz Tx and happymodel on version 1.2 telemetry enabled. (have the issue with a foxeer F7 on betaflight and F405 wing on arduplane- both latest FW)..
Did you figure this out. I can’t get the battery voltage either
I had a similar problem: I only saw 10 sensors in telemetry. I cleared the Softserial2 assignment and found 23 sensors.
FC: Matek F411 WSE
Same issue here. I’ve just installed BetaFPV F4 1S 5A AIO Brushless Flight Controller (onboard ELRS 2.4G). I’m using Taranis x9lite, TX module is BetaFPV nanoTX, latest v1 firmware 1.3.x (FC does not support ELRS 2.0). I can see only 10 sensors you mentioned, nothing more. Had no problems with voltage readings using Frsky R-XSR receiver.
Is there a foldable antenna for the ES24TX available? It is annoying, for the T-Lite to have this stock-antenna.
can Express lrs es24tx lite module in jumper t lite be Connected with frsky r xsr receiver? will it give gud range? How to connect and bind these?
No. ExpressLRS TX only binds with ExpressLRS RX.
Can we flash frsky r xsr receivers with Express LRS firmware so that it can act as a ExpressLRS RX??
For the 5V fan connection, could you connect the fan wires to the ground and 5 volt pins in the module bay that power the module?
If so, does voltage become present when external module is selected in the model menu?
If this is the case, it might be easier to connect to these points via the ELRS pin receiving socket as opposed to trying to solder to the point that you did on the board.?
Hi I’m also thinking the same if you hear anything let me know it seems strange they designed the box for a fan but no one knows what to do with it.(Anyway)
The external bay has the same voltage as the battery so that wouldn´t be a good idea. Only the internal Multi-Module is powered by 5V.
EP1 Rx – after initial flash – i get 0:0 Link Quality in my OSD – yet i bind correctly, have 99 RSSI, and can seem to fly (have not tested long range) but at least around a 2 acre yard no range issues. Still shows 0:0 LQ. I can’t figure out why.
I tried to reflash my Rx – but it won’t let me. Every time it WIFI connects, it instantly disconnects me and I can’t get to 10.0.0.1 (however my Tx can get to 10.0.0.1 no problem).
I can’t reflash via UART either — i get this error message all the time like the Rx is not opening its port to accept the reflash? I downloaded the STM files and the VCP files and the Impulse RC Driver fixer. So frustrated!
What the heck? Pretty disappointed. I have good LQ signals and readouts on a different EP1 flashed with the exact same build. I also had good LQ readout on a Happy Model ELRS 5in1 board for the 1s Whoop setup.
Hello, another great tutos.
I learned a lot from you, your explanations are clear.
Thank you so much for sharing!
How often do we need to update elrs LUA ? Seems like weekly we get new firmware for the tx and RX.
Not very often, check firmware release log, it should tell you when LUA script update is necessary. So far (V1.0) I think it’s not necessary yet.
Hi bro, btw thank for tutorial, its clear all step by step.
I just try, tx up-to-date rc9, rx up-to-date rc9, bind completely, rssi telemetri good working on radio.
But, in receiver tab, not respond, port uart good, serial crsf.
Can you suggest me, what wrong or what should i do ?
What i miss here xD
Attempting to detect FC UART configuration…
** Serial RX config detected: ‘serial 5 64 115200 57600 0 115200’
Enabling serial passthrough…
CMD: ‘serialpassthrough 5 420000’
======== PASSTHROUGH DONE ========
======== RESET TO BOOTLOADER ========
* Using full duplex (CFSF)
Serial port COM3
A fatal error occurred: Failed to connect to ESP8266: Timed out waiting for packet header
*** [upload] Error 2
========================= [FAILED] Took 20.02 seconds =========================
Environment Status Duration
———————————————– ——– ————
HappyModel_EP_2400_RX_via_BetaflightPassthrough FAILED 00:00:20.024
==================== 1 failed, 0 succeeded in 00:00:20.024 ====================
I’ve the same problem.
Have you found a solution?
I had that error because I tried to flash on USB-only, but my flight controller (TinyHawk III AIO board) did not turn on the UART and thus the RX. After plugging in a battery and retrying, it worked.
This particular page is bookmarked and has been referred to many times as I swapped my fleet over. Thanks, this a well-thought out resource!
So far I had “toys” MJX Bugs 6, Fimi A3, and I’m thinking about Eachine Novice 4 RTF, so I started studying lots of new things (betaflight, opentx…), but now the question is – wait a while for some nice RTF package with ExpressLRS…? That is going to happen sooner or later I believe…?
Excellent articles and videos, thank you.
Thanks for the great guide! Just followed it to get it working on my QX7 and EP1 RX. Only thing that might need an update is the target that is listed for the RX, it said to use the “HappyModel_EP_2400_RX_via_BetaflightPassthrough” even though you (and I as well) ended up using the WIFI version so it might be good to mention to use the wifi target instead.
It doesn’t seem to matter. You still get the same WiFi capability with the Betaflight Passthrough target.
So are EP1 and EP2 equal in Range? If Yes, why should someone choose EP1?
It depends, EP1 allows you to extend the antenna outside of the frame so it doesn’t get obstructed, so in reality it might give you more reliable signal.
Ok. Thank’s. So for an airplane it might be better to take the EP1…
I tried to solder the fan you suggested, and yes It was the same happy model board , I was getting 3.3 volts. The capcitor I soldered it to blew AFTER I got it to work. When that little capacitor blew all the lights on my TX board went out , and it no longer works. Awesome.
As always a great tutorial, would you have one for the ExpressLRS 900Mhz TX and RX
Maybe, but I think ELRS 2.4GHz would be more popular so I did it first.
What would have happened if FrSky hat skipped Access and ACCSTv2 and had stayed the opensource route. If they would have been the first who builtin ExpressLRS into their Transmitters than they still would be the leading elephant. Even if they are more expensive – the Gear Akquisition Syndrome of many people would habe bought the First Implementation of new stuff.
Thanks for this tutorial.
Helped me get my T-Lite / Tinyhawk communicating. Really appreciate the care to not skip steps and consider us n00bs who might not have done this type of RC link upgrade before.
Mr. Liang, you are a beautiful human being. Your info above about moving the jumpers on the Happymodel TX in order to flash the TX via UART saved me. This information can’t be found anywhere but here. Thank you so much for your efforts.
Hi, could you kindly change rx pinouts names?
Its writren vcc and can be confusing for newbies that’s 16.8v, whereas its onły 5v
Updated over UART QX7 won’t connect with the LUA script. I get ???????? 0:0
I’m also having this issue. Were you able to find a fix?
Here are a couple of things I’ve learned fighting with my QX7.
first update the QX7 to latest and greatest OpenTX
create a model with the internal radio off, and the external set to crsf
Unless you’ve done the QX7 crossfire mod (soldering a small board to the motherboard of the QX7) long press the menu button (3 bars on it), “Page” over to hardware, and set the baud rate to 115200.
How do you write a binding phrase to an spi rx, like the Mob7 1s?
I had this same issue. I was trying to update a Happymodel TX module that came with ELRS v1.0 to 2.0, so put the v2.0 lua script onto my SD card. This was incorrect, an ELRS module running V1 firmware won’t be usable with the V2 LUA script. I replaced the LUA file with the V1 LUA, and it ran just fine. I was then able to update the TX module to V2, and then replaced the V1 LUA with the latest V2 one.
These are my RSSI settings in Betaflight for ExpressLRS (2.4Ghz EP1 RX) in order to use the full 0 to 100% range of RSSI in my OSD:
set rssi_scale = 255
set rssi_offset = -48
set osd_rssi_alarm = 13
set osd_rssi_dbm_alarm = 99
You can decide whether to use RSSI alarm and/or RSSI Dbm alarm in the OSD tab.
You’ll notice that RSSI drops off very fast in the beginning but slower the lower it gets. Only at about 15 – 20% RSSI will you notice frames being dropped in the LQ but the connection will still be solid. You can go slightly below 10% RSSI without worries as the RSSI is not as erratic there as with most other receivers. Pay more attention to your Dbm and LQ though in the beginning to get a feel as to which RSSI values are safe. LQ does seem to drop off more rapidly the further down it goes. I’d say below 85 is the danger zone.
I would like to set osd_link_quality_alarm but in Betaflight 4.1 the range is 0 – 300, whereas in ExpressLRS LQ varies (and is usually above that range) depending on your frame rate (600 – 700 for 250Hz)
Thanks for sharing Craig, that’s some useful info!
btw, how did you get the rssi_offset = -48
One mistake though: Under the section where you describe how to flash the TX via uart. There is no boot button on the tx that you have to press. Just move the jumpers and install the cp210x drivers and hit “build & flash”.
Excellent article, will help a lot of people including me. Very informative and well put together. Thank you.
Great Work – thank you!
OPENTX 2.3.12 has a bug that it does not fully support 500hz as of 19 June 2021 and falls back to 250hz Sampling rate
If you are somebody who must have 500hz then use the 2.3.10 ERLS version of OpenTX or the latest RC of EDGETX
Need tutorial how to flash TX via USB, since my module stuck with syntax error mesage and can’t access tx menu (always return to ELRS tools menu) . It happened when I change telemetry ratio to 1:4.
Thanks for USB update firmware tutorial, my module is coming back online
Great guide and easy to understand explanation, the best so far, thanks Oscar ! On Opentx 2.3.12 stock firmware seems You’ve been limited in choice to 25Hz. That’s what I’ve read on FB.
OpenTX 2.3.12 supports all speeds except 25hz
If you want to use 25hz you will need EDGETX currently on GitHub as version 2.4 RC1 as 16 June 2021
Lite module is only for Jumper t lite. To use it in x-lite or tango 2 you have to print adapter and solder special connector.
Thank you I just updated the post.
Open tx 2.3.12 has an issue and currently can’t run 500Hz
Amazing documentation. I am really impressed with the quality of your work.
Oscar is doing great job and helping lots of people in the hobby. Consider to support him on patreon. Thx!
Nice guide! Opentx 2.3.12 stock firmware is released.may be no need to flash nightly build
Hahaha.. I knew I would have to update the post the moment I publish it!
I will check it out tonight, thank you.
Where can i buy an adapter to go from the MINI to JR bay?
I got mine from here: https://oscarliang.com/product-v6qi
But it’s only the pins and PCB, you need to get the case 3D printed.