I have bought two Sonoff S20 wifi switches. One to control a lamp in our bedroom, the other one for "playing". Ordering them on Taobao was not expensive - if I remember right, they were ca. 60 RMB (less than 10 Euro) per piece.
From the beginning I was not so happy with the way these switches are controlled over mobile phone. You need to install an APP called eWelink, register with your phone number and then use a cloud service to control the switches. I like it more if I have full control over my own devices and data.
So now I found the time to flash the switches with the open source Tasmota firmware. The basic procedure is quite simple:
- Open the switch to get access to the serial port
- (Optional) back up the current firmware
- Erase the current firmware
- Flash the Tasmota firmware
How this is done is described in detail in the Tasmota docs for all but the Chinese version of the S20 switch. So I will not repeat the general instructions here.
But there is one difficult part: The Chinese (CN) version of the switches seems to use a different PCB than EU, UK and US versions. These versions have the power sockets separated from a small PCB. The CN version has a larger PCB where the contacts of the power sockets are directly soldered onto the PCB.