Arduino and ESP8266 - Part 1: Level converters
Channel: AReResearch
Date: 2015-08-26

To connect an Arduino and an ESP8266 module, you need to convert the signal levels in order to protect the ESP8266.
Here I show you a few commonly used techniques.
My favourite is the bidirectional MOSFET level converter. You get them for cheap here: 
http://www.banggood.com/5Pcs-IIC-4-Way-Bi-Directional-Logic-Level-Converter-Module-p-951145.html?p=NT1005763073201409DA
Also see the blog article on the topic:
http://www.areresearch.net/2015/08/level-converters-how-to-safely-connect.html