ESP8266 – Low-cost Wifi Module for Embedded Applications

ESP8266 Module
ESP8266 Module

I can only read all the fun project posts on Hackaday using this cool Wifi module for so long before I have to try it out for myself.  I’m guessing this will be the first of many posts on my experience with this module.

From all that I read, this seems to be a fairly robust little chip (albeit poorly documented) and has a pretty lively community of hackers and developers willing to share their experience as well.  Many are attempting to use this as a standalone device, but my near-term aspirations are to use it with an array of my microcontroller platforms (at least all that have a USART available.)  The ESP8266 comes with a nice set of AT commands used to setup and use the integrated TCP/IP protocol stack.

My goal here isn’t to teach anyone how to use this module, but give a synopsis of what I’m doing with it, how it’s going, and to share any designs that may be helpful for those who want to give it a go as well.  There are many good websites that provide information about the module. Here, here, and here.

Ultimately, I’ll be using this device to communicate directly with the USART ports of my embedded projects, but until then, I’ll debug and develop using terminal programs from my computer or some Java code to simulate what will run in the microcontrollers.  There are several development boards out there to provide power and breakout pins so I decided to go with 2 options initially.

I liked the breakout board (ESP8266-EVB) and ESP8266 modules from Olimex to get up and running quickly.  They also break out all the GPIO from the chip in case I decide to utilize that down the road.  In the mean time, it’s done and ready for me to use while I wait for my boards to come in from OshPark.  Since I’m in the US, I purchased mine from Microcontroller Pros LLC for $11.50.  I’ll power it initially directly from my FTDI cable’s 5V supply since USB can handle up to 500mA and the ESP8266 draws peak current of around ~230mA.  If you do the same, make sure you use a cable similar to the TTL-232R-3V3 since the max voltage levels capable by the 8266 is 3.6V.  The TTL-232R-3V3 has a 5V VDD line (Red wire) and the RX/TX lines are all 3.3V.

ESP8266-EVB from OLIMEX
ESP8266-EVB from OLIMEX

For my own personal development, I wanted a certain form-factor and connectors in a certain orientation and location for prototyping.  I also wanted a fairly versatile board that I could use in the future with my embedded projects that has the requisite power supply and connections to the ESP8266 module.  I didn’t find exactly what I was looking for from the community, so I turned to my new favorite low-cost board house OshPark again to get some prototypes made up.

Here’s the schematic: ESP8266 Daughterboard R1

Boards available from OshPark, $11.40 for 3 boards: PCB Files

ESP8266_Daughter_TOP

ESP8266_BOT

Connectors J4 and J5 are wired identically and are used to plug directly into the TTL-232R-3V3 cable.  I like to add a second connector sometimes to make probing with a scope easier without splicing wires and soldering jumpers.

U1 is the 5V-to-3.3V regulator and can handle up to 1A.  The schematic has a regulator that’s rated for up to a max input of 6.5V, but I think I’m going to change it to one with a greater max input like the NCP1117ST33T3G which has a 20V input limit so I can use it on some of my automotive systems as well.

Connectors J1 and J3 break out all the ESP8266 lines and also have the input voltage from the regulator and have 0.100″ spacing to work with a breadboard for development.

Keep checking back for more updates once I get the boards and system up and running.

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