Sonoff S26 R2 Smart Plug - interior, batch change [ESP8266].

Welcome, today a brief description of the interior and batch changes of the WiFi-controlled Sonoff S26 socket/plug, available for purchase according to the socket standard popular in Poland. I will show how to upload Tasmota to it (which pin is IO0?) and give its configuration template.

Purchase Sonoff S26
Sonoff S26 at this moment can be bought for about 40 PLN on Polish auction sites and a little cheaper in China, but then you have to wait a long time for shipping and you may have to pay additional tax.
I myself bought it seemingly in China, but with shipping from the Czech Republic when it was on promotion:
. Set:

Instructions:


Interior of Sonoff S26
The chassis is held together by only three screws. No hooks.


PCB is not screwed down:

There's even a varistor on the input to protect against surges and some kind of capacitor against interference, not bad.

Transmitter and WiFi module:
Inside standard, rectifier bridge, inverter controller...

The inverter is made on BP2905:

Sonoff S26 V2.6 2021-04-28, this is the new version.

On the secondary side, there are two transistors controlling the relay and, as usual, a 3.3V LDO regulator powering the ESP.
Programming pads (but with IO2 instead of IO0?)


Changing the ESP8266 firmware Apparently all signals output to the pads are there, But if you look closely, there is an IO2 on the pad and not an IO0. For this reason, I derived IO0 directly from the WiFi module:
How did I know that IO0 was there? The pins are signed on the WiFi module itself, you can see it if you look closely.
Other than that, RX, TX, 3.3V power supply and ground are standard:

I uploaded the upload via esptool; the ESP was already in a programmable state after power connection thanks to IO0 being connected to ground beforehand:

All done, you can configure Tasmota:

Template:


. Alternative programming I haven't checked this anymore, But I have read on the web that the Sonoff S26 V2.6, the version I've shown here, however, is programmable without soldering IO0 - just enough to push a button:
So maybe I didn't solder to IO0, but I haven't checked that anymore.

Summary
Slightly better product by Polish standards. Some no-name manufacturers of such gadgets don't even give a varistor or there filter inside. Here there was even a fuse resistor.
Other than that, everything as usual, changing the firmware relatively easy, although I do not know why IO2 and not IO0 was brought out and I had to solder to the module.