This pin is on the rear of the ESP8266 module, and on many development boards, it isn’t even connected. That’s because its internally hooked up to the ESP8266’s SPI flash chip, and using it ...

Onboard the WiFi232 is an ESP8266 module emulating the Hayes AT command set. Baud rates from 300 to 115200 are supported, with power provided through a USB mini jack or solder terminals.