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WiFi Link - ESP8266 firmware for Arduino

This is a fork of WiFi Link firmware. The goal of this fork is make improvements and provide documentation.

The WiFi Link firmware is an ESP8266 arduino sketch developed by in Arduino IDE using Arduino esp8266 core. It was developed for the Arduino Star Otto, Arduino Primo and Uno WiFi Developer Edition.

With changes in this fork, it can be used with any esp8266 in combination with an Arduino MCU.

The corresponding Arduino library is WiFi Link library.

Building from source code

The WiFi Link firmware is an Arduino sketch so you can build it in Arduino IDE and upload it to ESP from Arduino IDE.

Building WiFi Link firmware from source files gives you possibility to build the newest version, build a branch version, build some fork version or change something in source code you need.

You need the esp8266 core for Arduino IDE. To install it using boards manager, follow the instructions.

Additionally, install the Arduino ESP8266 filesystem uploader IDE plugin

Download the source code

Use the source code from this fork. Every GitHub repository has a green "Clone or download" button which opens a small menu. Choose "Download ZIP".

Open or extract the downloaded zip and copy the folder ArduinoFirmwareEsp from zip to your sketches folder.

Start Arduino IDE and open the ArduinoFirmwareEsp.ino sketch. It opens additional files as tabs in IDE.

WiFiLink network port

Board selection and Verify

In Tools menu select board options and choose your board/shield/module or Generic ESP8266 from the ESP8266 section of the Boards menu. Set hardware depended options like crystal frequency, flash frequency, flash mode, flash size, led, reset.

Then choose esp8266 usage options:

  • CPU frequency option - recommended 80 MHz; 160 MHz produces more heat and has a higher power consumption
  • LwIP version - v2 Higher Bandwidth
  • Debug options: Disable and None is the basic setting
  • Optimal flash size selection for WiFi Link is "4M (1M SPIFFS)". at least 256 kB is needed for SPIFFS
  • "Erase flash" option is new in esp8266 Arduino package 2.4.1. To preserve SPIFFS and WiFi credentials use option "Sketch only". If changing from prebuild firmware, changing LwIP option or after a update to new version of esp8266 Arduino core package use "All flash content" to erase all parameters set be Espressif SDK. Erasing all SDK parameters can help if you experience WiFi connection stability issues.

Now verify the sketch with the Verify button. The first compilation after changing the board will take time.


Setup your esp board/shield/module for flashing. Connect it to USB of the computer and if it doesn't support DTR, put it into programming mode with dedicated button.

Use the Upload button in IDE to upload the WiFi Link firmware.


SPIFFS is the file system for ESP8266.

In subfolder data of the source codes of the WiFi Link firmware are the static web files (html, css, js) for the Web Panel. You can add your own files and they will be accessible on expected url.

We installed a plugin tool in chapter "Install esp8266 packages". This plugin creates a "ESP8266 Sketch Data upload" command in Tools menu.

The tool builds the SPIFFS binary and uploads it to selected port. With serial port you must put your board/shield/module into flashing mode in it doesn't support reset on DTR. Then choose "ESP8266 Sketch Data upload" from Tools menu.

Web Panel

Before connecting to WebPanel after serial flashing of firmware, power cycle the module/board/shield.

Web Panel network configuration uses the configuration Access Point (AP). User connects to the WiFi network created by a device, goes to fixed IP address URL and configures the network access in a Web Panel. The device connects in STA mode to the selected WiFi network and is accessible at IP address assigned by a DHCP or a static address set in Web Panel.

The AP network name is set as SSIDNAME in config.h. The WiFi Link fixed address in AP mode is

Warning: If you connect from sketch with WiFi.begin(ssid, pass), it changes the settings for the STA mode of the esp8266 for the Web Panel too. If you connect from sketch to unaccesible network or with wrong password, the Web Panel will not be accessible in STA mode.

Firmware OTA upload

The WiFi Link firmware supports OTA upload of new version of the firmware binary. OTA upload will only work if some version of WiFi Link is working in the ESP8266 and is configured to STA or STA+AP mode.

After configuring WiFi Link to WiFi STA or STA+AP mode, the IDE will detect it on network using mdns. The network 'port' will be accessible in Port submenu of Tools menu. Choose the network port for the OTA upload and use the Upload button in IDE.

Notes: Do not put the board in bootloader mode. Do not search for some special programmer in Tools menu.

The upload of the ArduinoFirmwareEsp.ino will overwrite the firmware binary and leave the SPIFFS part of the flash unchanged.

OTA upload works with SPIFS too and is fast.


WiFi Link firmware writes hostname and static IP settings into SPIFFS file config.json. SPIFFS upload overrides the SPIFFS content and the setting are lost.

If you have not default hostname or a static IP configured and you often upload the SPIFFS, download http://<IP>/config.json and add it to data subfolder of the WiFi Link firmware source codes.

Atmega328p sketch OTA upload support

For ATmega boards with at least 64 kB flash and for some ARM boards (SAMD, nRF52), you can use ArduinoOTA library for upload over network with WiFiLink installed.

The WiFi Link firmware build with #define MCU_OTA (config.h) supports ATmega328p sketch OTA upload. To build from the source codes with MCU_OTA you need a library called dfu. Download it here and Install it to your libraries folder.

For OTA with esp8266 module/board/shield, the reset pin of the ATmega must be connected to an ESP GPIO pin. Default in dfu library in esp8266-serial-arduinouno-hacked.cpp is GPIO5. You can change it to GPIO0, as it is on pinout header on most ESP modules. Star Otto and Uno WiFi have special setting hardcoded.

Only settings for the ATmega328p with Uno bootloader (Optiboot) exist in the dfu library.

Select "Arduino Uno WiFi" as board for network upload to Uno/Nano/Mini and other ATmega328p boards with Optiboot.

WiFiLink network port

SPI connection

WiFi Link can be used for MCU connected to esp8266 over SPI. To use it for any esp8266 module/shield/board, change the ESP_CH_UART to ESP_CH_SPI in the GENERIC_ESP8266 section and for the library add `' to avr boards.txt.

SPI pins are on the ICSP header of UNO/Mega/Nano (digital pins 11, 12, 13). Pin 10 is needed as SPI SLAVESELECT and pin 7 is used by WiFi Link as SLAVEREADY signal from the esp8266 GPIO pin 5 (D1).

SPI connection is used for AVR ISP (In System Programming). WiFi Link with MCU_OTA option and dfu library can write a sketch uploaded OTA to Atmega with SPI. But it is complicated. Write an issue on WiFi Link firmware, if you need it working.

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