The ESP8266 is a low-cost Wi-Fi microchip, with built-in TCP/IP networking software, and microcontroller capability, produced by Espressif System in Shanghai, China.

The chip first came to the attention of Western makers in August 2014 with the ESP-01 module, made by a third-party manufacturer Ai-Thinker. This small module allows microcontrollers to connect to a Wi-Fi network and make simple TCP/IP connections using Hayes-style commands. However, at first, there was almost no English-language documentation on the chip and the commands it accepted.[2] The very low price and the fact that there were very few external components on the module, which suggested that it could eventually be very inexpensive in volume, attracted many hackers to explore the module, the chip, and the software on it, as well as to translate the Chinese documentation.

The ESP8285 is a similar chip with a built-in 1 MiB flash memory, allowing the design of single-chip devices capable of connecting via Wi-Fi.

These microcontroller chips have been succeeded by the ESP32 family of devices.

ESP8266 Types and Boards

There are a lot of different ESP types on the market. Bare chips as the ESP-12E, embedded types as the Sonoff devices and development boards as the nodeMCU or WeMos D1 Mini

They differ from eachother in several points as number of availlable GPIO, memory size and more.

This article shows the different types and data.

Bare ESP8266 Chips

These chips are made for being soldered on a PCB (Printed Circuit Board). They are difficult to handle if you want to use them on a breadboard. If you need to use a bare chip on breadboard, use small adapter boards.

[Pic: Chip on adapter]

It is possible to just solder some short wires to the chip for breadboard use. This way is not recommended as it tends to shortcircuiting and is not very reliable.

Remember that these chips only offer a serial connection. Flashing them needs an UART board or UART cable. [Link to Basics..]

All these bare chips need 3,3V power supply. Use an according power supply or a voltage regulater (e. g. AM1117-3.3 or LF-33) or a regulator board for breadbords.

ESP-01

[Pics] [Pinout list / pic) FCC: No.

There are several versions of the ESP01 on the market. They differ in pinout and memory size.

If your dealer offers ESP-01 with a blue PCB - do not buy! These have only 512KB of flash ram which is too low for ESPEasy-2.x.

The newer ESP-01 with a black PCB have 1MB flash, they run issuefree with ESPEasy-2.x.

ESP-01S - Warning

At this time ESP-01S are sold with a flash chip marked "PUYA". These flash chips have a problem with using SPIFFS memory and do not work with ESP Easy. The problem is under investigation. At this time there is no given solution besides using other ESP-01 if available or changing the flash chip on the ESP-01S. UPDATE: A fix seems to be on the horizon. Stay tuned!

Some dealers offer "ESP-01 with 8MB RAM" - be carefull. Big numbers always look good. But the real meaning is "8 Mbit" - 1 MB of flash, it's the same item.

The older ESP-01 on black PCB have the pinout you'll find on many webpages. Newer ones, mostly called "ESP-01 V.3" seem to have a different usage of the "Reset" pin. If you don't need this pin for your circuit, just don't worry. Flashing can be done by switching off and on power instead of resetting easily.

Another type is the ESP-01S, due to the internet an "optimized" ESP-01. Depending on the manufacturer this might have the issue with the reset pin or not. Anyways it can be flashed easily by power off/on to start flashing.

The older versions (V.1 wiht 512KB/1MB flash) have an additional power LED on the board. This was ommited by the V.3 and the ESP-01S.

Even the ESP-01 has a 2x4 Pin connector it is not breadboard friendly. You may use short connection cables to connect it to your breadboard.

ESP-07

[Pic] [Pinout pic /& list) FCC: Yes

The ESP-07 is an older ESP.

It has a ceramical antenna besides a u.FL antenna plug (Sometimes called "Ipex" plug). As it has 512KB flash only it is deprecated and not usable for ESPEasy-2.X.

ESP-201

[Pic] [Pinout pic /& list) FCC: No

The ESP-201 is technically nearly the same as the ESP-07, but it is assembled from single parts on a board without cover. Breadboard friendly, but outdated due to 512KB flash size.

ESP-07S

[Pic] [Pinout List/Pic] FCC: Yes

The modern successor of the ESP-07. It has only the u:FL (Ipex) connector. You need an antenna of some form, a small PCB-antenna that can be glued to the inside of a case or a SMA pigtail connector to use an external antenna mounted to the case. This is optimal if you have to setup the ESP in a bigger distance to your WiFi access point

It has 4MB flash and is suitable for ESPEasy-2.x.

Esp-12

[Pic] [Pinout List/Pic] FCC: Yes

The ESP-12 is pretty outdated, still a few offers are left on the market. It is the ancestor of the nowadays ESP-12E and ESP-12F, just some GPIO-Pins missing.

There are different versions of this chip, equipped with a flash from 512KB to 4 MB.

Be carefull with buying or prefer ESP-12E/F types. The 4MB flash versuins are suitable for ESPEasy-2.x.

Esp-12E and ESP-12F

[Pic] [Pinout List/Pic] FCC: Yes

The ESP-12E and ESP-12F today are the all days ESP. The only difference is the layout of the PCB antenna. The ESP12F has an optimized antenna, that's the only difference.

Compared to the ESP-07S and the older ESP-07 and ESP-12 the ESP-12E has more GPIO pins lead to the outside.

Beware! These additional GPIOs are made for SPI connection and using SD-cards. Use GPIO10 with care, do not use GPIO9. Test your circuit thoroughly. Keep in Mind GPIO10 will switch to "high" for some seconds on bootup. Do not connect a switch or sensor to this pin that forces it to "low". [link to expl. of GPIOs and their usage]

Development boards

The development boards are the choice for breadboard testing. They have their power supply on board, a UART for flashing and monitoring the serial port is ready to use. They have a micro USB connector so you just need an USB cable and a breadboard to start. The power regulator on the development boards can handle sensors and such.Anyways it's capacity is limited. If you use a lot of peripherals or some power consuming ones, use a separate powersupply.

nodeMCU

[Pic] [Pinout List/Pic] FCC: Yes

The older Version (V0.9) is deprecated and no longer availlable on the market.

Newer Versions (V.2 and V.3) use the ESP-12E or sometimes the ESP-12F.

The differences between V.2 and V.3 are: - Board size. The V3 is slightly bigger. - UART chip. V.2 uses the CP2202/2402, the V3 uses a CH340G (Watch out, different drivers!)