If you are using a NodeMCU firmware on you ESP take note on the GPIO table mapping. All access is based on the I/O index number on the NodeMCU dev kits, not the internal GPIO pin.
This is a ESP8266 NodeMCU board from LoLin.
ESP8266-EVB from OLIMEX IS EVALUATION BOARD FOR ESP8266 WITH RELAY, BUTTON, UEXT, ALL GPIOS AVAILABLE ON 0.1″ HEADER ESP8266 is very highly integrated SOC which includes Xtensa LX106 core processor, RAM, RF front end and allow WIFI TCP-IP stack to be implemented
The ESP8266 from Espressif is a highly integrated chip designed for the needs of an increasingly connected world. It offers a complete and self-contained Wi-Fi networking solution, allowing it to either host applications or offload all Wi-Fi networking functions from