Firmware Programming and Binding Between Vantac-Lite TX Module and AIO 002

1.Open the external TX Module

ExpressLRS uses the CRSF serial protocal  to communicate between radio transmitter and ELRS TX moudle. If you want to set CRSF protocol please turn to the Model Setup. In the "Model Setup" tab, enable "External RF" and choose "CRSF'' as protocol.

2.Configuration and LUA 

All TX module parameter and configurations are can be changed with the help of LUA script.

a. You can get the LUA script by firmware files. There are two LUA script: ELRS.lua and elrsV2.lua. ELRS.lua is the configuration page that can only open the TX Module of version 1.0 and elrsV2.lua is the configuration page that can only open the TX Module version 2.0.

b. Copy the LUA script file ELRS.lua to the folder \SCRIPTS\TOOLS\ on the SD card of the remote control. The remote control enters the SD card configuration interface, and then drop-down selects the ELRS Lua script from the list to run the ExpressLRS LUA configurator.

Once ERLS LUA script starts to work and you will see the following configuration options.

The first two settiing in the LUA script: Pkt.Rate(packet refresh rate), TLM Ratio(Telemetry Ratio).

Pkt. Rate: it is the frequency at which telemetry data is sent. The larger Pkt.Rate means the lower delay. Usually the flight distance within 1km. We recommend you use the highest packet refresh rate , that is 500Hz.

TLM Ratio: It ishow often telemetry data is sent. The larger number means the slower telemetry updates, for example: 1:8 means sending telemetry datas every 8 frames, while 1:128 means sending telemetry data every 128 frames. More frequent telemetry will result the delay of the control link but the less telemetry will provide you the telemetry lost warning. It's also depends on your demands, if you want the more frequent upgrades and you need to set a smaller number.

When enter "TX Module" you can set the transmit power of the TX Module.

The transmit moudle of the power transmit moudle: according to the tests, 100mW can use 2.4GHz drone to fly within 33km.

 When you enter "VAT Administrator" and you can revise the frequency group and frequency of the VTX, control the VTX to change frequency group and frequency by remote control.

After entering "WiFi Connectivity", you can let the TX Module or receiver to enter WiFi mode.

Possible causes and solutions for this problem

(1) If the screen of the LUA script only shows" Loading...?/???", it shows  LUA does not communicate with the ExpressLRS TX module.


The possible reasons and solutions of the problem:

(1).The module is not properly connected in the remote control external JR module bay. Try reinstalling the TX module inside the JR bay/chassis. A working ExpressLRS module should have the LED lit.

(2).You are using an OpenTX version earlier than 2.3.11. At least version 2.3.12 is required to use ExpressLRS.

(3). The external RF has not been set to CRSF in the model settings. Go to the model settings on the remote and double check the settings. Internal RF should be turned off.

(4). The ExpressLRS TX module is in WiFi update mode. The radio needs to be powered off to enable the ExpressLRS module in normal mode.

3. Flash/ Upgrade ExplessLRS

There are many ways that can flash ExpressLRS firmware into a TX or RX module.But these depend on the hardware you use and its functions  (is there a USB socket, is there a WiFi ESP32 chip, etc.)

The available ways for TX module are: TX update, WiFi update, UART update.

The available methods for RX module are: BF Serial Passthrough, WiFi update, UART update.

Usually if there are onboard chip for your TX and RX, they can be upgraded by WiFi. If the TX module has a USB interface, the UART update method can be used. Any RX can be updated via BF Passthrough or UART update methods.

You can find possible firmware flashing methods for each hardware program from here:

ELRS firmware download URL:

ELRS configurator download URL:

4. Compile and flash TX/RX firmware

Download and install the ExpressLRS configurator. The version of the configurator in the tutorial is 1.0.8, and the methods for other versions are the same.

The first step is to start ExpressLRS Configurator and choose the Local flash  firmware. (Take firmware version 2.0.0 as an example).

The second step, click GHOOSE FOLDER, select the local file.

Compiling the Transmitter Module (TX) Firmware

Select the hardware and update type to build the firmware for it

The methods available for the TX module are TX update, WiFi (wireless) update, UART (wired) update.

For RX modules, the available methods are BF serial pass-through, WiFi (wireless) update, UART (wired) update.

Regulatory Domains -choose 915 or 868 frequency firmware settings according to your country and region.

Binding Phrase -Basically like your VTX channel number, you should let the people you fly with know so they don't use the same phrase and cause problems. It should be a unique phrase you can remember, not a password or secret. The length must be more than 6 characters.

NO_SYNC_ON_ARM: racing = enabled, long distance = disabled

HYBRID_SWITCHES_8: By disabling it will put all your switches in 2 position. Enable this if you want to use a 3-position switch, but note that your unlock switch (AUX1) will still be a 2-position.

ENABLE_TELEMETRY : Enable additional telemetry like battery voltage, current, GPS data, flight mode (basic telemetry like RSSI, link quality always transmit)

AUTO_WIFI_ON_INTERVAL: Enable automatic initiation of WiFi updates at boot. The timeout value can be customized (default is 40 seconds).

Once everything is set, press the BUILD button (not Build and Flash). This may take a few minutes.

After the programming is completed, a window will pop up, which contains a firmware file named "firmware.bin", which is the firmware after compilation, and you can select the binary file for programming through WIFI update later.

If the ExpressLRS configurator fails to detect the TX module and you will see the following error:

In the situation, please choose "Back",select serial port manually.

5. Refresh ExpressLRS TX

First, you must put TX in WiFi update mode.

Enter the ExpressLRS.Lua script on the remote control, select "WiFi Connectivity", turn on the WiFi mode "Enable WiFi" and keep the remote control on.

Then connect to the WiFi network named "ExpressLRS TX". The password for the WiFi network is "expresslrs"

Don't make mistake with the "ESP WiFiManager" Wi-Fi network - this is the hotspot network for the ESP chip, currently (with firmware version 1.0) not in use.

After connecting to the ExpressLRS TX module WiFi network, go to the browser and open this address:

You will see the ExpressLRS WiFi Update page welcome screen.

 Drop down page, press “Choose File” to select the compiled firmware file and click the "Update" button to start the update process.


After updating the 2.0 version of the firmware, after opening the WiFi mode and entering the website, there will be a "Join Home Network" option under the programming firmware, you can add a work or home WiFi network, and the TX module will automatically connect when you enter the WiFi mode next time.

When the update is complete, the following prompt will be displayed:

After the update is finished, wait for the LED of the TX module to light up before disconnecting the power! !

If the following prompt appears:

①Check whether the TX module maintains communication with the remote control.

②Whether you have entered WiFi mode, or disconnected in the middle.

6. The setting in betaflight

In the configuration tab, under the "Receivers" section, select "SPI Receiver Support" and click "Save".

7. Binding TX Module and Receiver

Enter the SD card page, open EXpressLRS, press the "[Bind]" button below it, and the TX Module will automatically enter the frequency binding mode.

                Connect the AIO to the computer and connect it to Betafight, enter the receiver configuration page, and click on the "receiver pairing" displayed in the lower right corner of the page. At this time, the AIO's receiver indicator light will change from slow flashing to double flashing, indicating that the receiver has entered binding mode.  

When the AIO receiver indicator light changes from double flashing to slow flashing, it means that the tuner and the receiver are successfully binded, waiting for the connection, wait for a while and the TX Module is successfully connected to the receiver, and there will also be a telemetry signal connected successfully. Voice prompt, after the connection is successful, the data signal will be displayed on the main page.

The indicator light of the receiver will change from double flashing to slow flashing, indicating that the binding is successful. After a while, the indicator light will turn solid on, indicating that the connection is successful. After the binding is successful, the receiver will remember the binding information, and it will automatically connect after restarting and you needn't to connect it again.

The following is the meaning of the status of the receiver indicators:

indicator light status meanings
Always bright  bind successfully or connection successfully
Fast flashing entered WiFi mode
Double flashing entered bind mode
Snow flashing no TX module signal connection