CRSF and ELRS
This page describes how to connect an ExpressLRS (ELRS) receiver to your BEASTX device. ELRS uses the CRSF serial protocol, originally developed by Team Blacksheep (TBS) for their Crossfire radios and now the standard on most OPENTX/EDGETX systems. Thanks to its high transmission rate and low latency, CRSF is widely used for drones, helicopters and wings alike.
If you like, here you can download the BEASTX background template for your EDGETX radio:
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Connection scheme
Control only: connect the receiver's TX line to the DI1/IO1 port of your BEASTX device. This sends control data via CRSF but gives no telemetry backlink.
Control + telemetry: additionally connect the receiver's RX line to the SYS port of your BEASTX device. If SYS is already used by an SRXL2 device (Spektrum AVIAN ESC), connect RX to the DI2 pin instead (MICROBEAST PLUS / ULTRA only).
CRSF telemetry serves two purposes: configuring the BEASTX system directly from the transmitter via a LUA script, and displaying live sensor data (voltage, RPM, temperature, etc.) on your radio. To use it, the SYS port must be set to CRSF at RECEIVER MENU point L (see RECEIVER MENU M for details).
Telemetry only becomes active if the system detects an ELRS receiver at power-up. If no RC signal arrives within 5 seconds of power-up (e.g. because the transmitter is switched off), the SYS port automatically falls back to normal operation. This is a convenience feature: it lets you connect via the StudioX Flow app over USB2SYS/BLE2SYS without having to reset menu point L manually.
| DI1 / IO1 | SYS | SAT | DI2 |
|---|---|---|---|
| TX line | - | - | - |
| TX line | RX line | ESC telemetry | - |
| TX line | SPEKTRUM SRXL2 ESC | - | RX line |
MICROBEAST PLUS
The ESC or throttle servo is connected at CH5 port. If needed the telemetry data line from the ESC is connected to the SAT port at the 5-pin JST port at side of the device using an adapter.
MICROBEAST ULTRA
The ESC or throttle servo is connected at IO2 port. If needed the telemetry data line from the ESC is connected to the SAT port at the 5-pin JST port at side of the device using an adapter.
NANOBEAST
The ESC or throttle servo is connected at CH1 port. If needed the telemetry data line from the ESC is connected to the SAT port.
Radio setup
When using a ELRS receiver make sure to enable the CRSF output using the web interface of your receiver. Using the RADIOMASTER ER-series receiver you can change the output signals of the receivers as needed. Here usually we set the CH2 and CH3 outputs of the receiver to RX and TX for the CRFS input and output. The smaller RADIOMASTER receivers only come with RX and TX outputs, so there is nothing special to do here. To access the web interface, power up the receiver, wait for one minute until the receiver flashes quickly, then connect your computer or smartphone to the new wifi network 10.0.0.1 (Password: expresslrs).
For the ELRS settings in the radio we recommend using the D500 Wide mode or 333Hz Full mode. Note that only in "FullRes" mode all channels have full resolution. When using channels 6 and above only for controling the ESC, gyro and similar control functions, the "Wide mode" should be OK as well. (Please note that CH5 is not available as this is used as binary switch channel!). We mostly use D500 mode which is working very well. The BX devices can even use the 1000Hz mode but we do not recommend this mode due to restricted radio range and lack of safety options. Also this will not give any benefit when driving servos at a much slower rate.
BEASTX setup
In order to use your CRSF/ELRS receiver you have to scan the input type in the RECEIVER MENU of your BEASTX device and set the correct channel ordering
for your radio system. By default the BEASTX system has a preset channel order that fits the AETR scheme of your OPENTX/EDGETX radio. If needed you can change the channel ordering in RECEIVER MENU of the BEASTX system.
| Channel | Function |
|---|---|
| CH1 | Roll / Aileron |
| CH2 | Pitch / Elevator |
| CH3 | Thrust / Collective |
| CH4 | Rudder |
| CH5 | - (Don't use!) |
| CH6 | Throttle |
| CH7 | Gain |
| CH8 | Attitude/Rescue (optional) |
| CH9 | Governor (optional) |
| CH10 | Aux channel (optional) |
(The optional functions are described in the section Optional features.)
MICROBEAST PLUS / MICROBEAST ULTRA
Push and hold the button on your MICROBEAST and power up the device. Menu LED A will flash instantly. Now release the button. Push again to start the scan process. When scan was successful, Menu LED B will show up. Now push and hold the button for 2 seconds and release in order to load the default channel assignments. If needed you can set up your telemetry devices at Menu LEDs L & M, if applicable; push button briefly to skip. Finally teach throttle failsafe position at Menu LED N by bringing the throttle in lowest position on your radio and push the button again. Now your MICROBEAST will start with init sequence. You can perform basic setup procedure in SETUP MENU when init sequence was completed. For further information about RECEIVER MENU setup, see next section.
NANOBEAST
Connect the TX line of the receiver to DI1 port and power up NANOBEAST. Connect the push button to SYS port. Push and hold the button for 2 seconds, then release. The Status LED will change color or go off. Push the button again to start the scan process. When scan was successful, the Status LED will flash twice. Now push and hold the button for 2 seconds and release in order to load the default channel assignments. If needed you can set up your telemetry devices at Menus L & M, if applicable (Menu L = Status LED flashes long once and then 5 times, for Menu L 6 times); push button briefly to skip. Finally teach throttle failsafe position at Menu N (Status LED flashes long once and then 7 times) by bringing the throttle in lowest position on your radio and push the button again. Now your NANOBEAST will start with init sequence. For further information about RECEIVER MENU setup, see next section. Then perform basic setup procedure in SETUP MENU.
Setup with StudioX
You can also use the StudioX app to start receiver scan and perform further setup steps. In this case open the Control menu in StudioX and click the SCAN button in this menu's screen. Please note that when the RX line of the receiver is connected to SYS port, you must disconnect the receiver from SYS temporarily, switch off your radio and power cycle your device. It will then enable "normal" SYS operation for programming purpose. For further informations please refer to the StudioX instruction notes.
(Picture sys adapter!)