ExpressLRS SBUS with OMPHobby M1 / M2 Helicopter

Since ExpressLRS release v3.3.0 SBUS protocol support has been added to ELRS receivers TX output. This means you can use any ELRS receiver with OMPHobby flight controllers like M1 and M2 helicopters and S720/T720 airplanes.

The RP2 ELRS receiver is perfect for small models like M1 and M2 since it is compact and very light with compact ceramic antenna. Please make sure you have v3.3.0 or later firmware on the ELRS receiver.

You will need the SBUS receiver adapter cable OSHM2076.

Connection

Solder the SBUS receiver adapter cable to the receiver as shown in the below picture.

Soldering SBUS Receiver adapter cable to RP2 ELRS receiver

Use the heat shrink wrap provided with the receiver to cover and protect the receiver.

Connect the JST connector to the SBUS port on the Helicopter Controller.

Transmitter Configuration

Model Configuration

Use the EVO XSR model configuration from our configuration file for the respective Radio Transmitter.

Channel resolution setting

ELRS has different switch modes for different channel resolutions. We want to have at least 5 channels with full resolution. The Hybrid ja Wide switch modes are not sufficient for Helicopter use as they offer only 4 channels with full resolution. We need to use the “8 channel full resolution mode

Run the ELRS LUA script. SYS->TOOLS->ExpressLRS

Change Packet rate to 333Hz. Currently this is the maximum rate that supports 8 Channel Full-resolution mode.

Change Switch Mode to 8ch

For more details about switch mode and channel resolution Please refer to the ELRS Switch Config guide.

Transmit power

It is important to not enable Dynamic TX power. This is because of a weird logic tied to channel 5. Please keep The TX Power set to fixed. 25mW should be more then sufficient for line of sight flying for model helicopters.

Binding

It is highly recommended to remove the main and tail rotor blades from the helicopter to prevent any injury/damage on accidental motor start up.

  1. Power off your transmitter/radio.
  2. Power-cycle the receiver 3 times. This can be done by rapidly connecting and disconnecting the battery 3 times. On the 3rd time don’t disconnect the battery 🙂
  3. Make sure the LED is doing a quick double-blink, which indicates the receiver is in bind mode. LEDSEQ_BINDING
  4. Power up your transmitter/radio and use the [BIND] button on the ExpressLRS Lua script, which sends out a binding pulse. The Popup will briefly show up and then disappear.
  5. If the receiver LED turned into a solid light, it’s bound! CONNECTED

SBUS protocol selection

Run the ELRS LUA script. SYS->TOOLS->ExpressLRS

Scroll down to Other Devices and press ENT.

You will now see the currently bound receiver. Select it and press ENT.

In the receiver options Scroll to PROTOCOL and choose SBUS.

Scroll down and EXIT the receiver options. Exit the ELRS lua script.

Power cycle the helicopter and this time the Flight controller should detect the receiver SBUS and make the initialization completion beeps.

Pre-flight check and flight

Perform the pre-flight checks to see that all controls are responding correctly.

Attach the rotor blades and go for a test flight.