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 resetFlashing
$ 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...$ esptool.py -p /dev/ttyUSB0 flash_id
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:xx:xx:xx
Stub is already running. No upload is necessary.
Manufacturer: 5e
Device: 4014
Detected flash size: 1MB
Hard resetting via RTS pin...