ESP8266: What's inside a “people's wifi”?

Our first article on the ESP8266 Wi-Fi chip was warmly received by the Habra community. Despite the fact that it contained little specific information. There was a good reason for this - the NDA, which we signed to receive the SDK from the solution manufacturer, Espressif . That is why we just said, "there is such a solution." So that interested people have the opportunity to pay attention.

The other day, we (the COOLRF project, do not forget to subscribe to our VKontakte community , if you are not already a member) received permission from the chip manufacturer to publish information in our articles that previously fell under the terms of the non-disclosure agreement. Anyone interested in details - welcome under cat.

Typical use cases

ESP8266 is designed for use in smart sockets, mesh networks, IP cameras, wireless sensors, wearable electronics and so on. In a word, ESP8266 was born to become the brain of the upcoming “Internet of things”.

There are two options for using the chip: 1) in the form of a UART-WIFI bridge, when the module based on the ESP8266 is connected to an existing solution based on any other microcontroller and is controlled by AT commands, providing the solution with a Wi-Fi infrastructure; 2) implementing a new solution using the ESP8266 chip itself as a control microcontroller.

The first scenario was briefly described in our last article. It is implemented using any of the inexpensive Chinese ESP8266-modules. It suits arduino lovers and those who already have ready-made schematics and debugged firmware on the basis of something their dearly beloved.

The second scenario involves writing an individual firmware to control the chip “from the inside”. At the moment, the firmware must be written for the proprietary compiler. With what, basically, are the requirements for non-disclosure of information around this decision. In the foreseeable future, the manufacturer plans to switch to the use of GCC and these restrictions will be lifted.

The scenario of using the chip as a control microcontroller is interesting in that it allows you to create devices that are really small and really long running on battery power. To work with peripherals on board the ESP8266 has all the necessary features.

Key Features

The ESP8266 chip is one of the most highly integrated WiFi solutions. Inside the chip there is a lot of everything that in competing solutions is often part of the external binding:



As a result, a typical chip strapping consists of only a few elements. Less elements = lower cost of components, less cost of soldering, less placement area, less cost of printed circuit board. Which is perfectly confirmed by the current prices of modules based on the hero of our today's review.

Manages all this integrated farming with an expanded version of the Tensilica's L106 Diamond series 32-bit processor. What is interesting inside?

• 802.11 b / g / n protocol
• Wi-Fi Direct (P2P), soft-AP
• Integrated TCP / IP protocol stack
• Integrated TR switch, balun, LNA, power amplifier and matching network
• Integrated PLL, regulators, and power management units
• + 20.5dBm output power in 802.11b mode
• Supports antenna diversity
• Power down leakage current of <10uA
• SDIO 2.0, SPI, UART
• STBC, 1x1 MIMO, 2x1 MIMO
• A-MPDU & A-MSDU aggregation & 0.4μs guard interval
• Wake up and transmit packets in <22ms
• Standby power consumption of <1.0mW (DTIM3)

Ultra Low Power Technology

Energy consumption is one of the most important characteristics of a solution that claims to be the brain of billions of IoT devices. What is the reason for the popularity of BLE and various native implementations of radio interfaces? Indeed, in the end, all devices based on these implementations still strive to get into ordinary Wi-Fi using special bridge devices.

The secret is simple - it’s difficult to create a device connected to WiFi that has sufficient battery life. Consumers are not ready to change batteries in sensors every two to three months. Therefore, “access to the network” had to provide bridges connected to constant electricity. ESP8266 should solve this problem. Now Wi-Fi can be used even in stand-alone sensors running on small batteries. Through the use of advanced energy management mechanisms for the solution.

If you briefly look at the characteristics of the consumption of the chip, you can remain in the dark. 215mA in transmit mode - nothing special? Yes, but it is worth reading the datasheet and you begin to understand the prospects of the solution. ESP8266 consumes about 60uA in deep sleep mode (with working real-time clock) andless than 1.0mA (DTIM = 3) or less than 0.5mA (DTIM = 10) in the mode of maintaining communication with the Wi-Fi access point.

What's next?

Today we posted in our VKontakte group the original datasheet of the latest version. It has full characteristics of the solution and examples of schematic solutions. See the “Documents” section (bottom right). Soon there will appear documents describing the AT protocol of the UART-WIFI bridge and the proprietary chip programming API. Follow our activities, the future promises to be interesting.