DEV-12757 Datasheet PDF - SparkFun Electronics

Introduction
   The ESP8266 is a popular, inexpensive WiFi/microcontroller system-onchip (SoC). Although it can be programmed like any microcontroller, the ESP8266’s popularity was gained as a simple, serially-controlled WiFi gateway. Using an AT command set, any microcontroller with a UART can use the ESP8266 to connect to WiFi networks, and interact with the rest of the Internet world over TCP or UDP. It’s an easy (and cheap!) way to get your Arduino on the Internet!

   There are a variety of designs based around the ESP8266, including tiny, modular boards and more accessible development boards like the SparkFun ESP8266 Thing. The ESP8266 WiFi Shield finds a middle ground between the Module and the Thing – it comes pre-flashed with an AT-command firmware, so it can be controlled by any UART, but it also breaks out and provides command access to all of the ESP8266’s I/O. It comes in the familiar Arduino Shield shape, and should work with any similarly-sized Arduino-compatible development board out there.

   Whether you want an introduction to the ESP8266 – without leaving the comfortable hardware confines of your Arduino – or you just have a backstock of Arduino’s that need an inexpensive gateway to the Internet, the ESP8266 WiFi Shield may meet your needs.