ELRS Setup

With the CRSF support added to version 2.2 you can now use ELRS as a Wireless link for direct to Servo output without a Radio or as an excellent wireless link option over Bluetooth.

Version 2.2 is still in development. Please see, Git Workflow and Actionson how to download a prebuilt firmware and GUI from Git Hub actions.

ELRS

ELRS is an open source Radio Link system which has great range and fast update rates.

High-performance Open Source Radio Control Link

Re-programming a Receiver as a Transmitter

ELRS transmitters that fit in a Radio are generally fairly large. ELRS since they introduced Unified targets makes it somewhat easy to re-program any ELRS receiver as a transmitter. You will need to flash custom software to the receiver to convert it into a transmitter.

To do this,

1. Connect via Wifi to your ELRS receiver. You need to wait 60 seconds after power up for Wifi mode to start. The LED will fast blink when it's in this mode.

2. Open a web browser and navigate to http://10.0.0.1

3. Under Firmware Update: -> Choose File and select the proper firmware file. Currently only the Happy Model EP2 has been tested. The firmware is available here. https://drive.google.com/file/d/1BWsRJR1nB_NbQkrmndM0bHh-rVTPejDC/view?usp=share_link More will become available as they are tested.

4. Click update

5. You will see a warning that the Firmware is mismatched. * Make sure you have selected the proper file here. Although this won't completely brick receiver it can be a pain and you need a FTDI to flash another firmware to fix. Choose Flash anyway
6. After it reboots, reconnect to the WIFI, you should now see that it shows ExpressLRS Tx
7. Navigate again to https://10.0.0.1

8. You now need to enter a Binding Phrase. This can be anything you wish. After you set this it will only connect to other ELRS receivers with the same phrase. The receiver will need to be set to the same. After you have picked your phrase, click SAVE & REBOOT

Choosing the Receiver

When binding a receiver, be sure the Transmitter is receiving CRSF data otherwise it will appear that binding was unsuccessful. The Leds will never go solid without data being sent.

Direct to Servos

You can use any ELRS receiver you wish. If your going direct to servos a PWM receiver is a good choice. A few examples below,

ER5C 2.4GHz 5Ch ELRS PWM ReceiverRadioMaster RC

ER5C 2.4GHz 5Ch ELRS PWM Receiver

HomepageMatek Systems

EXPRESSLRS 2.4GHZ PWM RECEIVER, R24-P

ELRS Micro ReceiverBETAFPV Hobby

ELRS Micro Receiver

As a Trainer Link to a Radio

Note the below steps are probably no longer neccessary. Please watch this video on building a ELRS firmware with SBUS output directly. https://www.youtube.com/watch?v=es8MY549_hY=

We can use another micro receiver such as the ELRS Happy Model EP2 as a receiver. Since Edge and OpenTX don't support CRSF input we have to add another board that converts the ELRS output, which is called CRSF into SBUS. This SBUS input is supported on most radio that has an AUX input available.

Happymodel 2.4g ExpressLRS ELRS nano series receiver module PP RX/ EP1 RX/ EP2 RXHappymodel

HomepageMatek Systems

ELRS CRSF TO SBUS CONVERTER

The Matek one wires fairly easily to the EP2 Rx and can be attached directly to an AUX port.

The only pin that doesn't line up is the TX to the radio. I have just bent the pin over to the correct location in the above photo and it makes for a nice small adapter on the bottom of the radio.

Programming the Receiver

You can use the ExpressLRS Configurator to setup your ELRS receiver. Be sure to select the same version as the TX for best compatibility.

Installing the Configurator - ExpressLRS

Choose the option for BINDING_PHRASE and type in the same phrase as above. You can use Wifi Mode to upload it directly to the board.

HeadTracker GUI Setup

You will need to be using Headtracker Version 2.21 or newer to get CRSF support. Under the UART tab choose the following settings.

Wiring to the Headtracker

To connect the transmitter to the Head Tracker you need to connect it to the UART pins. RX connects to TX.

Shown above with the DTQSYS Head Tracker. Note that ELRS receivers need a 5V supply. If you are doing this with a Nano33BLE you will need an additional 5v BEC.

HomepageMatek Systems

Micro 5V BEC

Radio Setup

You need to setup your radio to Master/Serial as the trainer mode.

When getting everything to bind you will need to make sure that you power everything up within 60seconds, before the ELRS Rx or Tx enter Wifi Mode. On a successful connection both LEDS should turn on solid.