WiFi devices (focus on ESP8266 and ESP32) from Espressif Systems are low-cost and very useful for embedded projects. These are classic microcontrollers without embedded flash memory. Application needs to assure external Quad-SPI flash to execute code from it directly.

Espressif offers SDK to program these microcontrollers directly and run code from there. It is called RTOS-based SDK, written in C language, and allows customers to program MCU starting with main function. These devices have some basic peripherals, such as GPIO, ADC, SPI, I2C, UART, etc. Pretty basic though.

Wifi connectivity is often part of bigger system with more powerful MCU. There is usually bigger MCU + Wifi transceiver (usually module) aside with UART/SPI communication. MCU handles application, such as display & graphics, runs operating systems, drives motor and has additional external memories.

Typical application example with access to WiFi

Typical application example with access to WiFi

Espressif is not only developing RTOS SDK firmware, it also develops AT Slave firmware based on RTOS-SDK. This is a special application, which is running on ESP device and allows host MCU to send AT commands and get response for it. Now it is time to use LwESP you are reading this manual for.

LwESP has been developed to allow customers to:

  • Develop on single (host MCU) architecture at the same time and do not care about Espressif arch

  • Shorten time to market

Customers using LwESP do not need to take care about proper command for specific task, they can call API functions, such as lwesp_sta_join() to join WiFi network instead. Library will take the necessary steps in order to send right command to device via low-level driver (usually UART) and process incoming response from device before it will notify application layer if it was successfuly or not.


LwESP offers efficient communication between host MCU at one side and Espressif wifi transceiver on another side.

To summarize:

  • ESP device runs official AT firmware, provided by Espressif systems

  • Host MCU runs custom application, together with LwESP library

  • Host MCU communicates with ESP device with UART or similar interface.