This Instructable will teach you how to use those $5.00 ESP8266 modules, as well as provide you some basic knowledge about networking. I'll be using the Micromite Companion Kit in my examples which is programmed in BASIC, however all of these instructions should be adaptable easily to your favorite micro.
In short, the ESP8266 module is a TTL "Serial to Wireless Internet" device. Providing your microcontroller has the ability to talk to a TTL serial device (most do) you'll be in business! The original instructions have been translated from Chinese into cryptic data sheets. We'll try to change that with this Instructable.
The ESP8266 module is a 3v device, but it's no wimp. It draws quite a bit of power. In fact, you'll probably need to make sure that your circuit's power supply can handle at least 1 amp of power. (In my case, I was using a simple 7.5v 500ma power supply. When I started working with this module, I switched it for a 7.5v 1amp power supply and had plenty of power.) As it turns out there is good reason for this; some Youtube videos have surfaced recently with folks seeing anything from 500 meters to a couple miles of transmission capability from this module. That's a lot of horsepower for $5.00!
I obtained my module from an Ebay vendor in the United States. The shipping was faster than China, but more importantly, the vendor provides the module without the pins soldered in.
The 8266 module isn't really breadboard friendly, but it's easy to convert it to a four pin module if you purchase the pin-less version. (or take a few minutes to remove the pins if you have obtained the other version)
You'll need 5 pin connections to make the module work. (See image 1)
RX, TX, ground, and 3v connected to two positions on the module.
I sourced a 4pin female cable from my parts box and cut off one end.
I used a small amount of nail polish to carefully paint over the unused pin, then looped the 3v connection from the power pin over the unused pin into the center. (See image 2)
The end result is a 4pin module that is now breadboard friendly to plug into your project.