What is the "Internet of things"?

The Internet of things (IoT) is the network of everyday objects — physical things embedded with electronics, software, sensors, and connectivity enabling data exchange. Basically, a little networked computer is attached to a thing, allowing information exchange to and from that thing. Be it lightbulbs, toasters, refrigerators, flower pots, watches, fans, planes, trains, automobiles, or anything else around you, a little networked computer can be combined with it to accept input (especially object control) or to gather and generate informational output (typically object status or other sensory data). This means computers will be permeating everything around us — ubiquitous embedded computing devices, uniquely identifiable, interconnected across the Internet. Because of low-cost, networkable microcontroller modules, the Internet of things is really starting to take off.

What is ESP8266?

The Chips

The ESP8266 series, or family, of Wi-Fi chips is produced by Espressif Systems, a fabless semiconductor company operating out of Shanghai, China. The ESP8266 series presently includes the ESP8266EX and ESP8285 chips.

ESP8266EX (simply referred to as ESP8266) is a system-on-chip (SoC) which integrates a 32-bit Tensilica microcontroller, standard digital peripheral interfaces, antenna switches, RF balun, power amplifier, low noise receive amplifier, filters and power management modules into a small package. It provides capabilities for 2.4 GHz Wi-Fi (802.11 b/g/n, supporting WPA/WPA2), general-purpose input/output (16 GPIO), Inter-Integrated Circuit (I2C), analog-to-digital conversion (10-bit ADC), Serial Peripheral Interface (SPI),

I2S interfaces with DMA (sharing pins with GPIO), UART (on dedicated pins, plus a transmit-only UART can be enabled on GPIO2), and pulse-width modulation (PWM). The processor core, called "L106" by Espressif, is based on Tensilica's Diamond Standard 106Micro 32-bit processor controller core and runs at 80 MHz (or overclocked to 160 MHz). It has a 64 KiB boot ROM, 32 KiB instruction RAM, and 80 KiB user data RAM. (Also, 32 KiB instruction cache RAM and 16 KiB ETS system data RAM.) External flash memory can be accessed through SPI. The silicon chip itself is housed within a 5 mm × 5 mm Quad Flat No-Leads package with 33 connection pads — 8 pads along each side and one large thermal/ground pad in the center.

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

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.

The Modules

Vendors have consequently created a multitude of compact printed circuit board modules based around the ESP8266 chip. Some of these modules have specific identifiers, including monikers such as "ESP-WROOM-02" and and "ESP-01" through "ESP-14"; while other modules might be ill-labeled and merely referred to by a general description — e.g., "ESP8266 Wireless Transceiver." ESP8266-based modules have demonstrated themselves as a capable, low-cost, networkable foundation for facilitating end-point IoT developments. Espressif's official modules are presently ESP-WROOM-02 and ESP-WROOM-S2. The Ai-Thinker modules are succinctly labeled ESP-01 through ESP-14. (Note: many people refer to the Ai-Thinker modules with the unofficial monikers of "ESP8266-01" through "ESP8266-14" for clarity.) See the ESP8266 article on Wikipedia for more information about popular ESP8266 modules.

Technical Features

802.11 b / g / n

Wi-Fi Direct (P2P), soft-AP

Built-in TCP / IP protocol stack

Built-in TR switch, balun, LNA, power amplifier and matching network

Built-in PLL, voltage regulator and power management components

802.11b mode + 19.5dBm output power

Built-in temperature sensor

Support antenna diversity

off leakage current is less than 10uA

Built-in low-power 32-bit CPU: can double as an application processor

SDIO 2.0, SPI, UART

STBC, 1×1 MIMO, 2×1 MIMO

A-MPDU, A-MSDU aggregation and the 0.4 Within wake

2ms, connect and transfer data packets

standby power consumption of less than 1.0mW (DTIM3)

Variants

ESP8266-based boards are available from several vendors and with different breakout boards. Most of the boards differ in the number of pins made available, the amount of Flash memory for storing program and data, and the shielding on the SOC for certified boards.

Some boards also support an external uFL antenna connector as well as the buil-in on-chip antenna.

The most common variants are:

ESP-01

This is the first and simplest board using the ESP8266. It allows to attach serial lines, and only breaks out two GPIO pins for native usage. This is also the cheapest and can be purchased from many chinese suppliers at 2.5 dollars.

ESP-03

This is the second generation board, breaking out more GPIO pins, and using a different antenna, plus an external antenna connector.

Olimex ESP8266 Eval Board

This board, produced by Olimex, breaks out all the ESP8266 pins in breadboard headers, but can also be soldered as a module.

It contains 2Mb of flash memory, four times that available on the ESP-01 and ESP-03, for larger firmware and space for files useful to make a webserver.

Using the ESP8266 with Arduino

Several Libraries have been developed to use ESP8266 as a module for Arduinos.

Also there is a port of the Arduino IDE for programming the ESP Directly, see below.

Using the ESP8266 via Serial port

You can interact with the ESP8266 sending AT Commands via the provided TX and RX pins by using another microcontroller.

Pay attention to the voltage of your signal lines, as the ESP8266 only works with 3.3v and pins are not 5V tolerant.

I.e. if you want to attach it to an Arduino clone you must use a logic level converter such as this .

An alternative to the logic level converter is to build a voltage divider circuit for each

signal line.

Programming the ESP8266 Directly

In order to program the ESP directly you need to install a toolchain and firmware upload utility.

The ESP8266 Wiki explains the process in detail.

You should use the ESP Open SDK to build your toolchain.

Espressif also provides an SDK containing the AT Firmware and the proprietary libraries.