Internet Things

Last year, I wrote about using a tool called tuya-convert to replace the firmware on my Tuya smart plugs. The firmware in question is Tasmota, which is an open source replacement firmware for devices with Espressif ESP chips. All my Tuya smart plugs have an ESP8266 chip, which can take custom firmware.

There are two ways of flashing Tasmota onto Tuya devices – an easy way, and a harder way.

There’s also a kind-of third ‘super-easy’ way, that I’ll mention towards the end.

tuya-convert – the easy way

I mentioned tuya-convert, which is a command line tool that exploits a vulnerability in older Tuya firmware to install Tasmota. You’ll need a computer such as a Raspberry Pi that has both Wi-Fi and Ethernet, and a smartphone. The tuya-convert tool then creates a hotspot that your Tuya devices can connect to when in pairing mode, and deploys the firmware wirelessly.

The key thing to emphasise here is that it only works with older firmware. Tuya patched the vulnerability in an update that came out some years ago, and indeed I’d already installed this on my smart plugs. That meant that tuya-convert could see the smart plugs, but couldn’t deploy the Tasmota firmware. So, I had to do it the hard way.

Using a UART converter – the hard way

As you may have guessed from the photo above, the only way I was able to flash Tasmota onto these smart plugs was by taking one apart, and using a USB to UART converter with some jumper cables. If tuya-convert doesn’t work, then this is what you’ll need to do. You’ll need the following:

• A USB to UART converter – I bought this one from AliExpress for the princely sum of £1.35.
• Some Dupont Jumper cables – again, I bought these from AliExpress for £2.40. I picked up a big bag of male-male, female-female and male-female cables, but you only really need male-female cables if you want to save a few pence.
• A computer with a USB port

I would also recommend the following:

• Some electrical tape to hold things down
• A USB extension cable

For the plugs that I was working with, I didn’t need a soldering iron, but some others may require it.

Disassembly and what’s inside

Firstly, it is very, very important that your smart plugs are not plugged into the mains while you do this, unless you want to burn yourself and/or your house down. We’ll be providing power via a different method, so make sure your device is not plugged in via the usual method. With my smart plugs, the positioning of the screws means it’s impossible for them to be plugged into the mains anyway.

Next, remove the screws from the plug. There were five on mine – the central one had to be removed first, and then the remaining four. Once that was done, I carefully separated the top and bottom of the housing.

The bottom part includes the high voltage AC circuitry. We’re not concerned with this and can leave it alone. What we’re interested in is the ancillary circuit board in the top part. It’s held in place by two small screws – you can remove these if you wish, but you can easily access the five pin holes that we need with the board still screwed in place.

The pin holes are as follows, with the first closest to the edge:

• RX – data in
• TX – data out
• GND – ground
• GPI00 – the pin hole that puts the smart plug into flashing mode
• 5V – the 5 volt power input pin hole

Normally, ESP chips work at 3.3 volts, but there’s a converter chip elsewhere on the circuit board for these specific smart plug. Yours may be different, so check first to see if it’s 3.3 volts or 5 volts. The UART to USB converter that I have offers both, so we’ll use five volts for this.

Connecting the wires

Firstly, make sure your USB to UART converter is not plugged in to the computer. You’ll need to get your Dupont cables and connect them from your converter to the board. The pins on the converter should be labelled, so you need to connect them as follows:

• From RX on the board to TXD on the converter
• From TX on the board to RXD on the converter
• From 5V on the board to 5V on the converter
• From both GND and GPI00 on the board to GND on the converter

For this last one, I used three cables – two male-male cable from each of the GND and GPI00 ports on the board, and one female-male cable from the GND port on the converter – and then taped the pins at the end of the wires together. If it helps, there’s a standard wiring diagram on the Tasmota Getting Started page – although we’re connecting one additional wire (GPI00).

Getting read to flash Tasmota

Now that we’ve linked the converter to board, we can do the fun bit – flashing the device. There are several ways you can do this, of which I would recommend two:

• Tasmotizer – this is a simple Windows program for flashing. The key advantage is that it can optionally download and backup the previous firmware, just in case you want to restore it later.
• Tasmota Web Installer – this allows you to install Tasmota through your web browser, using WebSerial. As it stands, only desktop versions of Chrome, Edge and Opera support it, so you can’t use Firefox or Safari.

Personally, I had a better experience with the Web Installer, so this is what I used. Once you’ve opened your flashing tool, plug the USB to UART converter into your computer and then click ‘Connect’. Your browser will ask for your permission to link the web page with the COM port created by the converter, so you’ll need to grant permission.

Note: sometimes the COM port wouldn’t show for me in the browser. If this happens to you, try opening Device Manager, if using Windows, to ensure that the driver has installed correctly. If not, asking Device Manager to simply update the drivers should be enough. I had the most success if I opened the web page, connected the USB to UART converter and then clicked ‘Connect’ in that order.

If all is well, the web flasher will connect to your device, erase the existing firmware and then upload Tasmota. It’s a quick process – the binary file for Tasmota version 15 is only 655 kilobytes, so it’ll only take a couple of minutes at most.

If you get a connection error, try swapping the RX and TX cables over and then try again, and make sure that the light on the circuit board isn’t on or flashing. If the light is on, it’s a sign that you’ve not connected the GPI00 pin correctly.

Assuming that the flashing worked, you can take the jumper cables out and reassemble your device and plug it back in to the mains.

Configuring Tasmota

So, now that your device has been flashed, you need to configure Tasmota on the device. Get your phone out, and go to Wi-Fi settings. You should see a new Wi-Fi hotspot called ‘tasmota-something-something’, where the somethings are an alphanumeric string – connect to it. A hotspot login box should appear – if not, go to http://192.168.4.1/ in your phone’s web browser.

The first step is to connect Tasmota to your Wi-Fi network. Choose the network, or type it in, and provide the password. Tasmota will then connect, and, if successful, will redirect to its new IP address which it’ll display on screen. I suggest making a note of this.

You’ll now need to navigate to Tasmota’s new IP address in a web browser – you can do this on any device, not just your phone. The first thing we need to do is tell Tasmota what kind of device it has been installed on. The easiest way to do this is with a Template, and there are a huge range of templates listed here. I couldn’t find an exact match for mine, but the closest was this one, which gave me the following template code:

{"NAME":"Anoop SP15","GPIO":[0,0,0,0,56,21,0,0,0,17,0,0,0],"FLAG":0,"BASE":18}

To paste this template into Tasmota, I used this guide. From the Tasmota home screen, I clicked ‘Configuration’, then ‘Configure Other’, and pasted the whole string into the ‘Template’ field at the top. Tick the box that says ‘Activate’, and then the green Save button at the bottom. Tasmota will restart, and then you’ll find that your smart plug now works. Huzzah!

Integrating Tasmota with Home Assistant

If you want your newly Tasmotised smart plug to appear in Home Assistant, then there are a couple more steps that we need to take. Tasmota communicated with other devices using MQTT, so if you don’t already have MQTT set up in Home Assistant, you’ll need to do this. The easiest way is to install the Mosquitto addon; this will then suggest the MQTT integration for you.

Next, we need to create a user account for Tasmota to use with MQTT. In Home Assistant, open Settings, and then People. At the top, select ‘Users’, and then click the blue ‘add user’ button. Give them a username and password, and then save these details somewhere safe for the next step.

Back to Tasmota. Firstly, we need to change a setting to allow Home Assistant to automatically discover your new Tasmota device. From the Tasmota home screen, choose ‘Console’, and input the following command:

SetOption19 0

Press enter. Next, go back to the Tasmota home screen, and into ‘Configuration’ again. Select the ‘Configure MQTT’ option. In the first box, you’ll need to enter the IP address or local hostname for your Home Assistant installation. If you use Home Assistant OS, this is most likely to be ‘homeassistant.local’.

Next, we’ll need to enter the username and password for the MQTT account we created earlier. The rest of the fields can be left with their default values, unless you want to customise the name.

Back to Home Assistant. If this is your first Tasmota device, then you should receive a notification that a new Tasmota device was found, and that you need to install the Tasmota integration. Do this, and your device will now be available. If you add any further devices, these will automatically appear in the Tasmota integration once their MQTT settings have been configured.

And that’s it. You should now be able to control your devices without needing to use Tuya’s cloud services.

The super-easy way – pre-flashed Tasmota devices

If you don’t already own a suitable smart plug, but want to use Tasmota, my advice would be to buy a smart plug with Tasmota already flashed. Local Bytes sell pre-flashed Tasmota smart plugs, so you can skip the disassembly and flashing sections of this guide. Alternatively, try eBay, where these plugs can also be bought pre-flashed.

Personally, if I was in the market for a new smart plug, I would buy one that supports Zigbee or Matter. I’ve previously reviewed some Onvis Thread/Matter smart plugs, and some Meross Wi-Fi/Matter smart plugs.

That being said, I’m pleased to have been able to flash Tasmota on these smart plugs. I’m currently only using one of them, but I’ve been able to give them a new lease of life with about £5 of materials and an hour or so of my time. Indeed, the spare ones may well end up on eBay in due course for someone else to use. It’s far better than letting them become yet more e-waste.

What’s next

Last year I bought a Sonoff Wi-Fi RF Bridge, but was disappointed that it wouldn’t work the way that I expected it to. And getting it to work with Home Assistant was a bit of a pain, requiring a custom integration from HACS or an addon. I’ve already installed Tasmota on it, so it too has local control, and I’m looking at flashing the RF chip with a different custom firmware to make it more useful. That will probably require soldering and is for another future blog post, however.