The ESP8266 is a system on a chip (SOC) Wi-Fi microchip for Internet of Things (IoT) applications produced by Espressif Systems.

Given its low cost, small size and adaptability with embedded devices, the ESP8266 is now used extensively across IoT devices. Although it’s now been succeeded by the newer generation ESP32 microcontroller chip, the ESP8266 is still a popular choice for IoT developers and manufacturers.

In this article, we’ll explain the main features of ESP8266 modules and development boards and their application within the world of IoT.

What is the ESP8266?

The ESP8266 module enables microcontrollers to connect to 2.4 GHz Wi-Fi, using IEEE 802.11 bgn. It can be used with ESP-AT firmware to provide Wi-Fi connectivity to external host MCUs, or it can be used as a self-sufficient MCU by running an RTOS-based SDK. The module has a full TCP/IP stack and provides the ability for data processing, reads and controls of GPIOs.

ESP8266 Specifications

This is based on the ESP-12 module, which we discuss below.

ESP8266 Functions

ESP8266 has many applications when it comes to the IoT. Here are just some of the functions the chip is used for:

• Networking: The module’s Wi-Fi antenna enables embedded devices to connect to routers and transmit data
• Data Processing: Includes processing basic inputs from analog and digital sensors for far more complex calculations with an RTOS or Non-OS SDK
• P2P Connectivity: Create direct communication between ESPs and other devices using IoT P2P connectivity
• Web Server: Access pages written in HTML or development languages.

ESP8266 Applications

The ESP8266 modules are commonly found in the following IoT devices:

• Smart security devices, including surveillance cameras and smart locks
• Smart energy devices, including HVACs and thermostats
• Smart industrial devices, including Programmable Logic Controllers (PLCs)
• Smart medical devices, including wearable health monitors

Chip versus Modules versus Development Boards

As discussed above, the ESP8266 is just the name of the chip. There are essentially three formats you can buy this in:

• ESP8266 Chip: This is the basic chip manufactured by Espressif, which comes unshielded and needs to be soldered onto a module. This is unsuitable for most users, apart from perhaps volume device manufacturers that can factor this into the production process under the unit cost of a module.

• ESP8266 Modules: These are the surface-mountable modules that contain the chip, which are ready to be mounted onto an MCU, produced by Espressif, Ai-Thinker and certain other manufacturers. They are usually shielded and pre-approved by the FCC for use. This means they’re a good option for device manufacturers looking to scale production.
• ESP8266 Development Boards: These are the complete IoT MCU development boards that have the modules preinstalled. They’re used for developers and manufacturers to create prototypes during the design stage, before they start production. Development boards are produced by several different manufacturers and the specifications differ between models. Some core specifications to be aware of when assessing ESP8266 IoT development board options include:
  • GPIO pins
  • ADC pins
  • Wi-Fi antennas
  • LEDs
  • Shielding*
  • Flash Memory

*Many international markets require shielded Wi-Fi devices, as Wi-Fi produces considerable Radio Frequency Interference (RFI), and shielding minimizes this interference. This should, therefore, be a key consideration for all developers and embedded-device manufacturers.

Manufacturers of Modules and Boards

Some of the largest manufacturers of ESP8266 modules and development boards are:

• Espressif 

• Ai-Thinker

• WeMos

• Adafruit

• Olimex

ESP8266 Modules

• Espressif Systems

The Espressif Systems esp8266 is available in the following modules:

●      Ai-Thinker

Current Ai-Thinker esp8266 modules are the following:

Older and discontinued models include: ESP-01, ESP-02, ESP-03, ESP-04, ESP-05, ESP-06, ESP-7, ESP-08, ESP-09, ESP-10, ESP-11, ESP-12, ESP-12E, and ESP-13 and ESP-14.

ESP8266 Development Boards/Dev Kits

●      ESP8266 Opensource Community

●      WeMos

Current WeMos boards are the following:

●      Adafruit

The current Adafruit 8266 board is the following:

●      Olimex

The current Olimex 8266 boards are the following:

SDKs

There is now a wide range of software development kits (SDKs) available, enabling developers to program the chip directly without using a separate MCU.

Espressif provides two official SDKs for use with ESP8266, which are:

• A FreeRTOS based SDK
• A Non-OS SDK

Aside from the Espressif options, there are plenty of commercial and open-source SDKs on the market, including:

• ESP Arduino Core – C++ based firmware
• ESP8266 BASIC – Open-source BASIC-like environment for IoT
• ESP-Open-RTOS – FreeRTOS open-source framework for ESP8266
• ESP-Open-SDK – Open integrated SDK for ESP8266
• Espruino – Javascript SDK and firmware
• Micropython – Python for embedded devices
• Moddable SDK – Javascript SDK
• Mongoose OS – C or Javascript open-source OS
• NodeMCU – Open-source Lua based firmware, similar to Node.js
• Sming – Asynchronous C/C++ framework
• uLisp – Lisp-based framework
• ZBasic – Visual Basic 6 adapted for ESP8266
• Zerynth – Python framework for IoT

Which is the best ESP8266 Module or Development Board for IoT?

As the above comparisons show, there are many options available with ESP8266 IoT boards and modules. To help you with your decision making, we’ve summarized some of the most popular below.

Popular ESP8266 Modules

Popular ESP8266 Boards

Read Our Other Resources

We’ve published a range of IoT resources for our community, including:

• How to set up an ESP8266 Wi-Fi module using the Nabto server peer-to-peer connection.
• A complete Guide to Microcontrollers for IoT, which explains all your options when it comes to choosing an MCU for your project.
• How to Make a Low-Cost ESP32-Based Remote-Accessible Camera Using ESP32-CAM or ESP32-EYE Board, which shows how you can create a security camera and enable remote accessibility via the Nabto platform.