How to firmware update a RadioMaster MT12 surface radio

 

The Radiomaster MT12 is a complex beast. There are numerous parts to the controller that need their own, separately developed, firmware updates. It’s not the easiest process to follow from a completely new user perspective as it effectively has a few hardware parts that need firmware, and the EdgeTX operating system. All of which are regularly updated. There are guides on the various project websites, but they might not be the easiest to follow because they cover the update processes for all of the compatible radio manufacturers.

I'm going to breakdown the elements of the radio version that I have and use (with the ELRS internal board and the 4-in1 external module).

Breakdown of elements:

- EdgeTX operating system
- ELRS firmware (internal module)
- ELRS backpack firmware (internal module)
- RM 4-in-1 module firmware (external module)

Edge TX is the operating system of the radio and effectively the base firmware that everything else runs on top of. It’s worth keeping this as up to date as the radio allows, as it will improve functionality and correct any previous bugs of the radio software.

First let’s see if you need to update. With the radio turned on, press SYS, then page left to page 7/7. Here you'll see the version information. This will tell you what version EdgeTX is on. In my case, in the image below, I'm on v2.10.5 and at time of writing no newer versions were available.

If it was a lower version then the update process is relatively straightforward. Go to https://buddy.edgetx.org/ and follow the instructions by selecting the MT12 from the drop down menu. You can then update directly through the USB port on the side of your radio (under the rubber cover) or through the bootloader on the SD card.

Note; On my first attempt to connect the browser through the USB port on Windows 11, the device didn't show up on the list. I had to fix the USB driver using the following link:  https://impulserc.blob.core.windows.net/utilities/ImpulseRC_Driver_Fixer.exe 

Once I'd done that the SMT32 Bootloader device  appeared as it should. I was then able to update with no problems at all. This updated both the bootloader version and the EdgeTX version.

ExpressLRS is the protocol that the internal module uses as the radio link with the vehicle receiver. It's an open source protocol that is regularly updated and is probably the most advanced radio control protocol on the market today.

To check the ELRS version press SYS and on the TOOLS page scroll down to the ExpressLRS entry (LUA script). In here are lots of configuration options for the transmitter and offers some receiver control too. Scroll right to the bottom (or scrolling up one take you there too) and you'll see the version number above the Exit option. I my case as shown in the picture below, I'm up to date on 3.5.3 and no newer versions were available at the time of writing.

If you have a lower version then it's worth updating to take advantage of new features, performance enhancements and any bug fixes since your version.

To update you'll need the ExpressLRS Configurator. This is available from: 

 https://github.com/ExpressLRS/ExpressLRS-Configurator/releases 

Download the latest version for your computer operating system, and install it. Once you've installed it, run the program and follow the instructions (quite similar to the EdgeTX process). Select your device from the drop downs (RadioMaster 2.4GHz and RadioMaster MT12 Internal).

You can go about ELRS updates in a couple of ways. I recommend to either go through the USB port (EdgeTX Passthrough) or to update via WiFi. USB is definitely faster though.

I won't go through the device options and settings here, you can probably leave them as they appear and be fine. I'll do a separate post about those later.

Once you've got your radio plugged into USB select USB Serial (VCP) and it should appear in the device COM selection as STMicroelectronics. You may have to manually select it from the drop down if it doesn't select it automatically.

Note: If it doesn't appear in the list (like it did for me on Windows 11), then go to this site: https://www.st.com/en/development-tools/stsw-stm32102.html to download the latest version. Once that's installed you should be able to select it and update your radio.

ExpressLRS Backpack is only really a feature used by other control devices to control the radio. So for example if you are using FPV goggles and want to make changes to the radio, you can see what you are doing inside the goggles. I'm not personally using this functionality, but I feel like it's probably worth having this feature up to date with your ELRS version in case you find yourself thinking about FPV. The update process is basically the same as the main ELRS update. Choose your version, then your radio, and flashing method. Then hit the Flash button and it should work. To check your installed version you'll see the "backpack" listing in the ExpressLRS settings; scroll down and you'll see the version.

RM 4-in-1 module is the module that clips onto the top of the radio and gives us multi protocol support through 4 discreet chipsets built in. There is an internal module also available in the 4-in-1 version of the MT12. This guide is for my version of the MT12 which has internal ELRS and an external 4-in-1 module.

First things first, again, we'll check the version number. With a model selected that has the external module active, press SYS and go to page 7/7 again and select Modules/RX version. In there you'll see the Ext module version. As seen in the picture to the right mine is V1.3.4.12 (which is the latest pre-release version at the time of writing).

The downloads of the latest firmware can be found here: https://downloads.multi-module.org/ 
Select your configuration from the left drop down box. In this case with the external module we will select RadioMaster RM 4in1 External Module.
Then select the options on the right to narrow down the downloads to the one you need. Once you've selected the module in the left box you'll just need to select Firmware type: Surface and Channel Order: AETR. This should bring you to the bottom of the page where the firmware version you need is listed. In this case it's called "mm-stm-serial-aetr-sfc-v1.3.4.0.bin".

To install you can connect over a couple of methods. For this I like the flash from radio method. But I'll touch on the Flash Multi app too. Basically add the .bin file you downloaded to the SD card Firmware folder by using the USB port under the flap (use the storage connection method). Once it's transferred just navigate to the SD card and Firmware folder (page 2). Hit select on the firmware file and flash to ext module, and that should start the update.

Note: The MT12 has a low character count screen. Files with too long names will be excluded from the listings, so rename the .bin file to something shorter like "4in1-fw-v1.3.4.0" so that it appears in the list. 

The other method is by using the Flash Multi app, which uses the USB port on the top of the module. Download your firmware, download the app (from here: https://github.com/benlye/flash-multi), run the app and add your firmware to the app. Select the right com port, like for the ELRS and EdgeTX update tools and hit the button. Should be quite quick.

For the very latest test builds of firmware for the 4in1 multi module go to:
https://downloads.multi-module.org/latest-test/

And there you go a fully updated controller!

 

I hope this helps a few people out as I know this is a complicated controller, but well worth perservering for the performance to price ratio! Keep an eye out for more guides to this controller.