What is an ESP8266, and why does ESPHome use it?

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At its core, The ESP8266 is a low-cost Wi-Fi (b/g/n) microchip, released in December 2013. It has a full TCP/IP stack and microcontroller capability and is manufactured by Espressif Systems in China. This neat little chip first caught on in the West with the Ai-Thinker-produced ESP-01 module, which eventually led to the creation of a myriad of tools, such as ESPHome.

Because nobody had translated the documentation from Chinese to English, at first, the ESP8266 didn’t catch on immediately. Eventually, hackers caught on and started to explore the module, the chip, and the software on it. And with its growing popularity, the documentation was slowly but surely translated into the English language and made accessible to a much larger user base.

ESP8266 specifications

The ESP8266 has a CPU clocked at 80 MHz (default) or 160 MHz and has 32 KiB instruction of instruction memory and 80 KiB user-data memory at its disposal. For interactions with other devices, there are 16 available GPIO pins.

By using the Arduino core for ESP8266 Wi-Fi chip, the ESP8266 can be programmed like any other Arduino device . This made it a very popular product with makers, as the Arduino Core basically turned the ESP8266 into a cheap Arduino with Wi-Fi capabilities.

The emergence of beginner-friendly ESP8266 boards

Nowadays, there are many boards from all sorts of manufacturers to choose from. Many of these boards include a so-called USB-to-UART bridge on-board and a Micro-USB connector. That Micro-USB port can be used to not only power an ESP8266 board, but also to connect to it. These ESP8266 boards make for a straightforward development platform, even for beginners.

With ESPHome recently opening up the possibility to flash such an ESP8266 board with nothing more than a browser, the ESP8266 is in a league of its own when it comes to ease-of-use. From the available boards, there are two fan favourites: the LOLIN D1 mini and the NodeMCU development kit.

The LOLIN (WEMOS) D1 mini ESP8266 board (and its clones)

Undoubtedly, one of the most popular ESP8266 boards is the LOLIN D1 mini, also found under its old name, WEMOS D1 mini. Henceforth, I shall simply be calling it the D1 mini. I have personally used this board for several personal projects, and it’s perfect for absolute beginners, as well as experienced makers.

A more recent LOLIN D1 mini ESP8266 board
A more recent LOLIN D1 mini ESP8266 board

It features the above-mentioned Micro-USB port, which makes flashing it as easy as plugging it into to your PC and opening the ESPHome Web Tools. It features 11 digital input/output pins yet is very compact (25.6 mm × 34.2 mm). If you are willing to wait for shipping, these can be found on AliExpress and other Chinese online marketplaces for very little money.

D1 mini ESP8266 Board (clone)
  • Description The D1 mini is a very popular Wi-Fi board based on ESP-8266EX. Due to its size and ease-of-use, it is perfect for DIY projects.
  • GPIO: 11 digital I/O pins
  • Analogue input: 1 input (3.2V max input)
  • Operating Voltage: 3.3V
  • Clock speed: 80/160M Hz
  • Size and weight: 34.2 mm × 25.6 mm, ~3 g

It might sound like I'm just trying to get you to use my affiliate for a larger purchase, but I do recommend ordering more than just a single board. I can almost guarantee that at some point you will somehow destroy an ESP8266 board, such as I did when I mixed up 3.3V and 5V. And I can confirm that once you have finished an ESPHome project, you will be itching to start the next one.

Are D1 mini clones safe?

If you are unsure as to which board to buy, LOLIN does have an official AliExpress store. There are many D1 mini clones to be found, some of which do have minor issues. Most clones will work as expected, but more often than not the slightly more expensive original will be the safer purchase. On the LOLIN store, you will also find several ready-made shields specifically for the D1 mini.

ESPHome projects using the D1 mini

The D1 mini has been used as the brains of automated blinds, it is what controls the Home Assistant Tags kit, and it has been used in countless interesting DIY lights using WLED. For basic applications, such as gathering information from sensors, the power delivered via the Micro-USB port is enough to drive the board and individual sensors.

This ESPHome beginner's guide will not be covering the actual creation of a project. But I do have an ever expanding page on this site featuring ESPHome projects!

D1 mini ESP8266 shields

While browsing the official LOLIN store, you might have come across many so-called shields. LOLIN offers display shields, LED shields, display shields, battery shields and much more. These shields are a perfect way of starting off your ESP8266 and ESPHome adventure, as they don't require you to solder anything to a perfboard and making connections of your own.

Using a shield, you can simply solder some legs on to the LOLIN (WEMOS) D1 mini board, and then solder the shield to those. The drawback is that in most cases you will only be able to connect a single shield.

There are a few shields you will be able to stack, for example the power shield can be used with just about every sensor, as it only connects to the 5V and GND pin. Make sure to carefully read the documentation when stacking multiple shields, as they might require the same GPIO pin.

NodeMCU is technically not a board

Another name you will frequently hear in the ESPHome and other maker communities, is NodeMCU. Technically, NodeMCU is not an ESP8266 board, but an open-source firmware. To help makers get started, there are several development kits, using the ESP8266 microchip, which have become synonymous with the name.

A D1 mini ESP8266 board
A NodeMCU ESP8266 development kit

The NodeMCU development kit is significantly larger than the D1 mini. But they do have similarities: A Micro-USB port for easy flashing is found on both and, just like the D1 mini, the NodeMCU development has been cloned countless times. For most ESPHome projects, there is no need to go with the larger NodeMCU development kit or one of its clones.

ESP8266 NodeMCU (ESP-12E)
  • Built-in Micro-USB, with flash and reset switches.
  • Can be flashed using ESPHome.
  • Fits on a breadboard and thus is easier for prototyping.

Alternative and weird ESP8266 boards

There are of course many other boards for you to choose from. Some of these have more memory, can be hooked up to an external antenna, or include a Li-ion battery charger. LOLIN itself produces the D1 mini Pro, which has the possibility of attaching an external antenna and a larger flash. These come in useful for more specialized projects. For the majority, however, a D1 mini will do.

Sonoff, H801, Zemismart, etc.

Because the ESP8266 is so readily available at a low cost, it is being used in a number of prebuilt products, such as the popular Sonoff Wi-Fi switches from iTead and the H801 RGBW LED controller. If there is a device containing an ESP8266 or ESP32 microchip, and it can be flashed, you will be able to run ESPHome on it.

Sonoff Basic R2
  • Uses a ESP8266 microchip and can be flashed with ESPHome.
  • ESPHome requires no cloud services and can function even if the internet is down.
A portrait photo oif Liam Alexander Colman, the author, creator, and owner of Home Assistant Guide wearing a suit.

About Liam Alexander Colman

is an experienced Home Assistant user who has been utilizing the platform for a variety of projects over an extended period. His journey began with a Raspberry Pi, which quickly grew to three Raspberry Pis and eventually a full-fledged server. Liam's current operating system of choice is Unraid, with Home Assistant comfortably running in a Docker container.
With a deep understanding of the intricacies of Home Assistant, Liam has an impressive setup, consisting of various Zigbee devices, and seamless integrations with existing products such as his Android TV box. For those interested in learning more about Liam's experience with Home Assistant, he shares his insights on how he first started using the platform and his subsequent journey.

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