Using With Sonoff T3 EU 3 Gang¶
ESPHome can also be used with Sonoff T3 EU 1/2/3 Gang wireless switches. These devices are basically just an ESP8266 chip with up to 3 relays to control power output and three backlit capacitive touch buttons to control the relays.
This guide will step you through setting up your Sonoff T3 EU 3 Gang and flashing the first ESPHome firmware
with the serial interface. This should also work for the T1 EU 3 Gang and T2 EU 3 Gang with PCB version
T1EU TOUCH V1.0 from 2018.
After that, you will be able to upload all future firmware updates with the remote
Over-The-Air update process.
If you’ve previously installed Sonoff-Tasmota on your Sonoff T3 EU 3 Gang, you’re in luck 😀 ESPHome can generate a firmware binary which you can then upload via the Tasmota web interface. To see how to create this binary, skip to Step 3: Creating Firmware.
Since firmware version 1.6.0, iTead (the creator of this device) has removed the ability to upload a custom firmware through their own upload process. Unfortunately, that means that the only way to flash the initial ESPHome firmware is by physically opening the device up and using the UART interface.
Opening up this device can be very dangerous if not done correctly. While the device is open, you will be a single touch away from being electrocuted if the device is plugged in.
So, during this entire guide never ever plug the device in. Also, you should only do this if you know what you’re doing. If you, at any step, feel something is wrong or are uncomfortable with continuing, it’s best to just stop for your own safety.
It’s your own responsibility to make sure everything you do during this setup process is safe.
For this guide you will need:
Sonoff T3 EU 3 Gang 😉
A USB to UART Bridge for flashing the device. These can be bought on Amazon for less than 5 dollars. Note that the bridge must be 3.3V compatible. Otherwise you will destroy your Sonoff.
Jumper wires to connect the UART bridge to the header pins and to connect GPIO0 to the Ground.
Computer running ESPHome or the Home Assistant ESPHome add-on.
Screwdriver to open up the Sonoff T3 EU 3 Gang.
Have everything? Great! Then you can start.
Step 1: Opening up the Sonoff T3 EU 3 Gang¶
The first step is to open up the Sonoff T3 EU 3 Gang. Note that you do not have to run the original firmware supplied with the Sonoff T3 EU 3 Gang before doing this step.
Just to repeat this: Make absolutely sure the device is not connected to any appliance or plugged in before doing this step.
While the device is not plugged in, turn the device face down and put a narrow flat screwdriver into the slot at the bottom. With careful twisting motion detach the faceplate.
After that, use the same screwdriver to carefully lift the top PCB off of the switch. This PCB contains the ESP chip and what’s left inside the switch body are relays.
Step 2: Connecting UART¶
Now we need our computer to somehow establish a data connection to the board. For this we will have to connect the four wires on the UART to USB bridge to the UART pins of the Sonoff T3 v1.0.
Fortunately for us, these pins on the ESP controller have dedicated solder pads on the PCB (
J3). You can identify
these by the
GND markings on the silk-screen.
Now go ahead and connect these pins to your UART to USB bridge as seen in below image. Make sure
that you connect these correctly, especially the
GND parts as you can otherwise
destroy the chip.
VCC33 should be connected to the
3V3 (not 5V) pin of the UART bridge,
and the same with
There’s no need for soldering - for quick job like one time firmware flashing you can just hold pins in respective holes by hand provided you are not touching any live contacts, only the wires.
If your upload fails with an
error: espcomm_upload_mem failed message it’s most likely due
to the pins being swapped. In that case, just swap
TX and try again - you won’t break
anything if they’re swapped.
Step 3: Creating Firmware¶
The Sonoff T3 EU 3 Gang is based on the
ESP8266 platform (technically it’s the
ESP8285, but for our purposes
they’re the same) and is a subtype of the
With this information, you can step through the ESPHome wizard (
esphome sonoff_t3_us_3gang_v1.0.yaml wizard),
or alternatively, you can just take the below configuration file and modify it to your needs.
esphome: name: <NAME_OF_NODE> esp8266: board: esp8285 wifi: ssid: !secret wifi_ssid password: !secret wifi_password api: logger: ota:
esphome sonoff_t3_us_3gang_v1.0.yaml compile to validate the configuration and
pre-compile the firmware.
After this step, you will be able to find the compiled binary under
<NAME_OF_NODE>/.pioenvs/<NAME_OF_NODE>/firmware.bin. If you’re having trouble with
uploading, you can also try uploading this file directly with other tools.
Step 4: Uploading Firmware¶
In order to upload the firmware, you’re first going to need to get the chip into a flash mode, otherwise
the device will start up without accepting any firmware flash attempts.
To put ESP8266 into flash mode you need to connect
GND when the device is powering up.
This is a tricky process with T3 and the best is to hold the ground wire to the right side of the
R19 Resistor which is connected to
GPIO0 connected for 2-4 seconds. The T3 EU 3 Gang should now be in a flash mode and should not blink with any LED.
The touchpads may light up.
Now you can finally run the upload command:
esphome sonoff_t3_us_3gang_v1.0.yaml run
If successful, you should see something like this:
Hooray 🎉! You’ve now successfully uploaded the first ESPHome firmware to your Sonoff T3 EU 3 Gang. And in a moment, you will be able to use all of ESPHome’s great features with your Sonoff T3 EU 3 Gang. Now you can put your T3 back together and fire up.
While now your T3 will start up and connect to your WiFi network if you power it up from UART it will not behave normally, it may flash random LEDs, turn on and off touchpads’ backlight and not react on touching touchpads. This will all be fixed once you re-assemble your T3 and power it up from the mains power once safe to do so.
If above step does, however, not work, here are some steps that can help:
Sometimes the UART bridge cannot supply enough current to the chip to operate, in this case use a 3.3V supply you have lying around. A nice hack is to use the power supply of NodeMCU boards. Simply connect the NodeMCU’s 3.3V to VCC and GND to GND. Do not attempt to plug the device into a socket to overcome this problem while troubleshooting.
In other cases the
RXpin are reversed. Simple disconnect the device, swap the two pins and put it into flash mode again.
Step 6: Finishing Up¶
If you’re sure everything is done with the T3 EU 3 Gang and have double checked there’s nothing that could cause a short in the case, you can put the T3 back together.
Now triple- or even quadruple-check the UART bridge is not connected to the T3 EU 3 Gang, then comes the time when you can connect it.