Espressif ESP8266 User Manual

2.Assembly
A. ESP8266 Module
There are many different modules available based on ESP8266s, they differ in a number of
aspects such as the quantity of available GPIO pins or if they can be programmed easily
without need of an additional Serial-to-USB converter. If you are a beginer I suggest you use
a developer-friendly module like the NodeMCU V1.0 or the Wemos D1 mini. They come with
a USB connector and have the maximum number of available pins ready for your usage. The
absolute minimal requirement is that your ESP8266 module has at least two free GPIO pins
to connect it to the OLED display.

Espressif ESP8266 Specifications

General

Digital I/O Pins	17
Analog Input Pins	1
Wi-Fi	802.11 b/g/n
Operating Voltage	3.0V - 3.6V
Clock Speed	80 MHz / 160 MHz
Operating Temperature	-40°C to 125°C
Dimensions	24mm x 14mm
Processor	Tensilica L106 32-bit micro controller