Smart switch ESP 8266EX

Alternative firmware: https://tasmota.github.io/docs/Getting-Started/
Input for the board is from mains. It is then rectified and transformed down to 3.3V via DS1117 regulator to power the ESP8266EX chip and the relay that switches the mains relay.
Marked are 3.3V VCC and GND. The ESP8266EX UART-0 is on marked points TX and RX.
Boot message
ets Jan 8 2013,rst cause:4, boot mode:(3,6)
wdt reset
Flashing
$ esptool.py -p /dev/ttyUSB0 read_mac
esptool.py v4.5.1
Serial port /dev/ttyUSB0
Connecting....
Detecting chip type... Unsupported detection protocol, switching and trying again...
Connecting...
Detecting chip type... ESP8266
Chip is ESP8266EX
Features: WiFi
Crystal is 26MHz
MAC: 5c:cf:7f:79:e7:be
Uploading stub...
Running stub...
Stub running...
MAC: 5c:cf:7f:xx:xx:xx
Hard resetting via RTS pin...

