Introduction
The BETAFPV Micro RF TX module is based on the ExpressLRS project, an open-source RC link for RC applications. ExpressLRS aims to achieve the best possible link performance in terms of speed, latency, and range, making it one of the fastest RC links available while still offering long-range performance.
Github Project Link: https://github.com/ExpressLRS
Facebook Group: https://www.facebook.com/groups/636441730280366
The official ExpressLRS project currently does not support the OLED function. The BETAFPV team has submitted a pull request on Github and awaits the official merge. Until ExpressLRS official support is available, please obtain firmware from the BETAFPV Github repository: https://github.com/BETAFPV/ExpressLRS
Specifications
- Frequency bands (2.4GHz version): 2.4GHz ISM
- Frequency bands (915MHz/868MHz version): 915MHz FCC/868MHz EU
- RF output power: 25mW/50mW/100mW/250mW/500mW (2.4GHz), 100mW/250mW/500mW (915MHz/868MHz)
- Packet refresh rate: 50Hz/150Hz/250Hz/500Hz (2.4GHz), 25Hz/50Hz/100Hz/200Hz (915MHz/868MHz)
- Input voltage: 5-12V (2S)
- USB port: Type-C
Diagram showing the module's ports: XT30 (2S), USB Type-C, Fan+RGB, OLED Screen, 5D Button, and GH1.25 (GND, 5V, CRSF).
Note: Please DO NOT use a 3S or higher voltage battery to power the TX module. Doing so will permanently damage the power supply chip.
Compatibility and Basic Configuration
The BETAFPV Micro RF TX module is compatible with radio transmitters featuring a micro module bay (AKA JR/SLIM module bay), such as the Frsky Taranis X9D and TBS Mambo.
ExpressLRS utilizes the Crossfire serial protocol (AKA CRSF protocol) for communication between the radio transmitter and the RF TX module. Ensure your radio transmitter supports the CRSF serial protocol. The following steps demonstrate how to set up the CRSF protocol and LUA script using a radio transmitter with an OpenTX system.
Diagram illustrating the connection of the RF TX module to a radio transmitter's module bay, showing the SMA-KE Port and internal connections like NC, 5V-12V, GND, and CRSF Serial Port.
Note: Please assemble the antenna before powering on. Failure to do so will permanently damage the PA chip in the RF TX module.
CRSF Protocol Setup
To configure the CRSF protocol in OpenTX:
- Enter model settings.
- On the "MODEL SETUP" tab, turn off "Internal RF".
- Enable "External RF" and select "CRSF" as the protocol.
The "MODEL SETUP" screen typically displays:
- Use global funcs: Checked (✔️)
- Internal RF: OFF
- External RF: CRSF
- Channel Range: CH1-16
- Receiver: 00
LUA Script Usage
ExpressLRS uses the OpenTX LUA script to control the RF TX module, facilitating operations like binding and setup.
- Save the ELRS.lua script files onto the radio transmitter's SD Card in the Scripts/Tools folder.
- Long press the "SYS" button (on radios like RadioMaster T16) or the "Menu" button (on radios like Frsky Taranis X9D) to access the Tools Menu, where the ELRS script can be launched with a single click.
The following shows the LUA script running successfully:
ExpressLRS Obf0d9 0:250
Pkt Rate: 250Hz (-108dbm)
TLM Ratio: 1:64 (78bps)
Power: 500 mW
RF Freq: 2.4G ISM
[Bind] [Wifi Update]
The LUA script allows pilots to check and configure various settings of the RF TX module.
Module Interface and Operation
The module features a 5D button. Note that only the vertical movement of the button is functional; the other four directional inputs are invalid. Below are the basic operations of the button and OLED display.
Diagram showing the 5D button on the module and a hand pressing it.
- Long Press: Enter menu page or change the value of the current row.
- Short Press: Move to the next row.
Note on Menu Navigation: When the RF TX module enters the menus page, the binding between the module and receiver will be temporarily lost. Binding will automatically recover upon exiting the menus. If you change the Pkt Rate, you must re-power the receiver.
Note on WIFI Upgrade: When the RF TX module enters WIFI Upgrade status, the button will be unresponsive. Please re-power the RF TX module after completing the firmware update via WIFI.
Binding
The Micro RF TX module supports the officially released V1.1.0 protocol and does not include a Binding Phrase. Ensure your receiver operates with the V1.0.0~V1.1.0 protocol and has no Binding Phrase set. The module can enter binding status via the ELRS.lua script (as described in the "LUA Script" chapter). Alternatively, use the button and OLED to navigate to the BIND position and long press the button to initiate binding.
Binding Confirmation: Long press the button. The RF TX module will then enter binding status.
Note on Binding LED: The LED will NOT flash during binding status. The module will automatically exit binding status after 5 seconds.
Note on Binding Phrase: If you reflash the RF TX module firmware with a custom Binding Phrase, ensure the receiver uses the same Binding Phrase for automatic binding.
Output Power Switch
The Micro RF TX module allows switching output power via the ELRS.lua script, as detailed in the "LUA Script" chapter. Alternatively, use the button and OLED to navigate to the "Output" position. Long pressing the button will cycle through the available output power settings.
Example LUA script display for output power:
ExpressLRS
Pkt. rate: 500hz
TLM Ratio: 1:128
Power: 100mW
RGB: White
[Bind] [Update]
Long press the button to switch the output power.
Note on LED and Fan: The RGB LED status does not change with output power. The fan will spin automatically when the output power is 250mW or higher. The Micro RF TX module does not support 1W or 2W output; switching to these values will automatically set the output to 500mW.
More Information
As the ExpressLRS project is subject to frequent updates, please refer to BETAFPV Support (Technical Support -> ExpressLRS Radio Link) for the most current details and manuals.
https://support.betafpv.com/hc/en-us
- Newest user manual;
- How to upgrade the firmware;
- FAQ and troubleshooting.
