ESP8266 un useable pins - Project Guidance - Arduino Forum
Reference for ESP8266 using Arduino IDE - Complete Guide
Getting Started w/ NodeMCU ESP8266 on Arduino IDE - Arduino Project Hub
For Wemos Mini D1 ESP8266 ESP32 ESP 32S WIFI Bluetooth CP2104 Development Board Module For Arduino With Pins|development board|wifi modulemodule bluetooth - AliExpress
ESP8266 – Knowing the NodeMCU GPIOs or Pinout - The Engineering Projects