Flashing smart plugs with tuya-convert FAIL

I purchased a Medion Life+ Smart Plug from Aldi, for the purpose of doing some experimentation, and setting up a few automation ideas I had by connecting it to my Home Assistant instance.

After getting it home, and doing a bit of I realised that these plugs were actually manufactured by Tuya, and were simply rebranded with the Aldi Medion brand.

I found that there was a Tuya component for Home Assistant that worked with the Tuya cloud, however upon doing some more reading, a more appealing solution emerged.

I realised that many people were flashing Tuya based devices with custom firmware such as Tasmota or ESPHome, which allowed local control of the devices over a local network using Home Assistant. 

Usually flashing these devices means pulling them apart and using a USB-to-serial adaptor to flash the custom firmware. But, even more searching led me to tuya-convert which makes it possible to flash some Tuya-based devices over the air.

So, I dove in.

The instructions for tuya-convert recommended using a Raspberry Pi, but as my Raspberry Pi Zero W was tied up running Home Assistant, this wasn't really an option.

So, I instead went down the path of installing Ubuntu 19.04 on an old laptop, and trying to get tuya-convert running.

The Ubuntu install process is very slick these days, and I had it installed in a dual-boot setup with Windows 10 in no time. I then downloaded the tuya-convert git repository and installed the repository using the following commands

git clone https://github.com/ct-Open-Source/tuya-convert

cd tuya-convert

./install_prereq.sh

I then downloaded the Tasmota binary sonoff.bin (in this case 6.6.0) tried to start the tuya-convert flashing process using the following command

./start_flash.sh

But, this is where the trouble started. Over the next week or two I battled with Ubuntu and tuya-convert, firstly to attempt to get tuya-convert running correctly on Ubuntu, and then after that hurdle was overcome, getting the Medion smart plug to flash successfully.

What I finally realised was that the vulnerability tuya-convert was relying on had unfortunately been patched by Tuya in a subsequent firmware update, and the Medion plug must have had the updated firmware.

Word on the street was that some devices with old firmware were still able to be flashed successfully though, so I learnt that the Brilliant Smart Wifi Plugs were also a Tuya-based device, and purchased one of those.

Alas, my efforts failed again, suggesting that the Brilliant plugs also had the updated firmware which had been patched. 

But, like all clouds there is usually a silver lining; I recalled the Sonoff S20 I had purchased over 12 months ago, and realised that there were clear instructions for flashing Tasmota on the S20 using a USB-to-serial adaptor if I was willing to pull it apart. 

So, I ordered a CH340G USB to serial adapter from eBay, and prepared for the next instalment...