A Workhorse With WiFi Support That Can Do The Job Even For Sophisticated Projects

The ESP8266 from Expressif is probably the most widely used microcontroller in non-Arduino projects. It became an instant success and convinced many users to move from Arduino to ESP because of a number of substantial advantages:

Today, breakout boards with the successor ESP32 are only marginally more expensive than the ESP8266. ESP32 boards feature a better power regulator and is about twice as performant in any aspect. While the ESP8266 is perfectly capable of handling most DIY projects, for new purchases you should look into buying ESP32 instead: for example the original ESP32 DevKit C with the ESP32 WROOM, or better yet the successor ESP32 C3 which comes with native USB support and is available in miniature form factors more closely resembling the ESP8266 form factor.


Here are the most important ESP8266 specs at a glance:

Item Value Comment
GPIO 17 actually available pins depend on breakout board
SPI 1 for fast peripherals
I2C 1 software implentation, for slow peripherals
UART 1 serial communications, external serial-to-USB chip required for USB

USB-to-Serial Controller: CH9102, CP210x, CH340

Initially, microcontrollers were designed to use simple serial interfaces which is why they all include at least one UART. This does not enable them to connect to USB.

Since microcontroller boards need to be programmed, and programming takes place on a desktop computer, the microcontroller boards require a way to connect to USB (unless you want to connect them to an old-fashioned serial port).

Starting with ESP32 S2 and ESP32 C3, modern microcontrollers today come with serial communications capabilities built-in. This eliminates the need for external components, and you can connect these microcontrollers directly to the USB port of a PC.

ESP8266 breakout boards can use different USB-to-serial chips. On Windows, the type of chip just determines the speed and time it takes to upload new firmware. On other operating systems (like iOS), not all USB-to-serial chips are natively supported, and you may need to manually install additional drivers on your computer.

Item CH210x CP9102 CH340 Remarks
OS all all Windows other OS may need manual driver installation
Price medium medium low  
Speed Mbps 12 4 2  

The CP9102 is a relatively unknown variant that is pin-compatible to the CH210x. It is slower but still twice as fast as the CH340.

There are other chip types such as FT232RL, PL2303, MCP2221, and MAX3421 less commonly found.


Here are a few comparisons to help you judge whether ESP8266 is the right choice compared to popular alternatives.


The ESP8266 solves two common Arduino problems:

  • Memory: the initial (and still popular) Arduinos come with very limited programming memory. When sketches become a bit more complex, compiling frequently fails due to out of memory errors. This is not the case with *ESP8266.
  • WiFi: when your project requires wireless connectivity, the ESP8266 comes with built-in support for all WiFi modes: it can act as an own WiFi Access Point, can work in Station Mode, and both. It can easily become a webserver and act as web service. Arduinos do not come with any wireless support.

In addition, ESP8266 breakout boards are much cheaper than Arduinos. While the old Arduino Uno still sells for more than EUR 20,00, complete ESP8266 breakout boards with 4MB RAM are available for under EUR 2.00.

So overall, ESP8266 often is the “better Arduino”. But wait: the best is the enemy of the good. The ESP32, the successor of the ESP8266, may be an even better choice.


The ESP32 (initially released 2016) succeeded the ESP8266 (releaased 2014) and has since seen many new subtypes such as the S2, S3, C3, and C6.

The initial ESP32 WROOM microcontroller (released 2016) can today be purchased for under EUR 3.00. Given its advantages, it may well be the better choice when thinking about purchasing new ESP8266:

  • Faster: The ESP32 WROOM microcontroller is a dual-core microcontroller running at 260MHz. It is roughly twice as fast as the ESP8266.
  • Bluetooth: In addition to WiFi, the ESP32 WROOM also supports Bluetooth so you can control your projects from mobile devices such as smartphones.
  • Better Components: the ESP8266 breakout boards are known for using inferior voltage regulators that can hardly provide the current required to power the microcontroller. Once additional sensors are connected, it is not uncommon for the ESP8266 microcontroller boards to run into random resets or other erratic behavior due to power problems. ESP32 breakout boards all come with sufficiently dimensioned voltage regulators.
  • Direct USB Support: The ESP32 can natively act as USB Host and emulate USB devices such as keyboards and mice. Starting with ESP S2 and ESP32 C3 (not ESP WROOM), the microcontroller also allows direct firmware upload via USB, eliminating the need for external components and drivers such as CH340

My personal recommendation is the ESP32 C3 breakout board (available for under EUR 3.00). It uses one of the most modern ESP microcontrollers, specificly one with native USB support, and comes in miniature form factors that fits even the smallest DIY devices and specializes in energy savings modes.

ESP8266 from Expressif

The ESP8266 surfaced in 2014. This microcontroller is much more powerful than the ATMegas used by Arduino at that time.

from left to right ordered by size: ESP32 C3 from Seeed, ESP8266 D1 Mini clone, ESP32 WROOM 32D dev board.

Todays’ entry level ESP8266 typically come with 4MB memory on board (check before you buy though, there are also 512KB variants).


The D1 Mini (including clones) probably is the most popular board design: it is cheap, compact, comes with WiFi capabilities, has sufficient memory (tyically 4MB), provides enough GPIO pins for most projects (9 of which 5 are freely usable), has one ADC and supports SPI and I2C interfaces.

The ESP8266 D1 Mini is one of the most popular ESP8266 boards in use.

It is based on the Expressif ESP8266EX chip, basically the only ESP8266 chip widely used.

ESP8266 Pro

The Pro version of ESP8266 appears to be merely a marketing gag and refers to a different board layout. Its most visible “advantages* are a ceramic antenna instead of the simple PCB antenna and more memory: most ESP8266 Pro come with 16MB instead of 4MB memory (but watch out, some feature just 8MB or just 4MB).

The ESP8266 Pro is almost as expensive as a full-fledged ESP32 and not a good choice.

On the negative side is an unshielded version of ESP8266 (not covered by a shiny silver metal box) that has no FCC ID, and the same lame voltage regulator you find on the cheapest *ESP8266 clones.

ESP8266 Pro is a product from the past when the price difference between ESP8266 and ESP32 was still huge. Anyone in need of more memory could try and use the ESP8266 Pro.
Today with price differences diminishing, either the basic ESP8266 features are sufficient for your project (in which case you should get an ESP8266), or you need more (memory or better specs or a better voltage regulator). In which case you should get an ESP32.
For the price of a ESP8266 Pro you can get a ESP32 as well when you look around a bit.


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(content created Mar 23, 2024)