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Flashing Frsky R9 Modules


Flashing via OpenTX (Requires OpenTX 2.3.12 or newer)

Flashing the Bootloader

The bootloader is required to be flashed first prior to flashing the ExpressLRS firmware as the bootloader will replace the factory-bootloader, and enable the hardware to instead use the ExpressLRS code.

Using an OpenTX transmitter, you flash the bootloader, and then flash ELRS.

Here is a quick 2 minute demo if you would rather watch a video than read the steps:

With the previous step (Preparing your Radio) done, you should now readily flash your R9 Transmitter Module.

Copy r9m_elrs_bl.frk onto the SD card of your radio, in the /FIRMWARE folder.

Flash r9m_elrs_bl.frk (14kb) to your TX module:

  • Navigate in OpenTX to the TOOLS menu (hold SYS button)
  • Page to the SD-HC CARD page, then the FIRMWARE folder
  • Flash the frk file by holding OK and selecting "Flash external module"

Flashing the firmware


  • Frsky_TX_R9M_via_stock_BL
  • Frsky_TX_R9M_LITE_via_stock_BL

In the ExpressLRS Configurator, select the correct target for your module and set your Firmware Options.

Click on Build and wait for the firmware to be compiled. After that's done, ExpressLRS Configurator Log should show the Success Message, and it will automatically open the folder where the firmware.elrs can be found. Put (copy-paste) the firmware.elrs to your Radio's SD Card (preferably to the /FIRMWARE folder for easy access). Once on your radio, navigate to the /FIRMWARE folder, select the firmware.elrs and click-hold the Enter button and select "Flash External ELRS".

By this point, the bootloader (r9m_elrs_bl.frk) should've been flashed already. Wait for the flashing to finish, and if your module is equipped with a speaker (full size R9Ms), you should hear the tune and two beeps (if external module is now set to CRSF protocol).


  • Frsky_TX_R9M_via_STLINK
  • Frsky_TX_R9M_LITE_via_STLINK
  • Frsky_TX_R9M_LITE_PRO_via_STLINK

This method is an irreversible one. You will not be able to go back to Frsky firmwares with this method. You have been warned!

This method also involves taking apart your module and soldering wires directly into its board. If you're not comfortable doing this, STOP now.


R9M STLink Connection

R9M Lite

R9M Lite STLink Connection

R9M Lite Pro

R9M Lite Pro STLink Connection

Wire up your module as shown above to your STLink device. This is important before any of the steps below.

Before flashing, disable 'Readout Protection'. To do this download the ST-LINK Utility and follow this quick how to video. After such, you can now disconnect (Target -> Disconnect) and close the ST-Link Utility.

With the module still connected to the STLink, and your Firmware Options set, hit Build & Flash in the ExpressLRS Configurator and wait for the process to finish. Once that's done, and the Success Message showing, you can now remove/unsolder the STLink, and re-assemble the module, and put it into your Radio's Module Bay. The ExpressLRS tune should play and then two beeps after that can be heard, for units that has a speaker (R9Ms) and if the External Module is set to CRSF Protocol.

Verification can be done using the ELRS.lua script. It should show the Version Hash at the top, as well as the options you can set. If it's showing "Connecting", check if External Module is set to CRSF for the selected model in your radio, and that internal RF module is set to off. See general Troubleshooting section for other ways to determine your module is flashed and ready for flying.