ESP-LINK

This firmware implements a transparent bridge between Wifi and serial using an ESP8266 module. It also provides support for flash-programming Arduino/AVR microcontrollers as well as LPC800-series ARM microcontrollers via the ESP8266.

The firmware includes a tiny HTTP server based on esphttpd with a simple web interface, many thanks to Jeroen Domburg for making it available!

Eye Candy

These screen shots show the Home page, the Wifi configuration page, the console for the attached microcontroller, and the pin assignments card:

Hardware info

This firmware is designed for esp8266 modules which have most ESP I/O pins available. The default connections are:

• URXD: connect to TX of microcontroller
• UTXD: connect to RX of microcontroller
• GPIO12: connect to RESET of microcontroller
• GPIO13: connect to ISP of LPC/ARM microcontroller (not used with Arduino/AVR)
• GPIO0: optionally connect green "conn" LED to 3.3V (indicates wifi status)
• GPIO2: optionally connect yellow "ser" LED to 3.3V (indicates serial activity)

If you are using an FTDI connector, GPIO12 goes to DTR and GPIO13 goes to CTS.

The GPIO pin assignments can be changed dynamicall in the web UI and are saved in flash.

Initial flashing

(This is not necessary if you receive one of the jn-esp or esp-bridge modules!) If you want to simply flash the provided firmware binary, you can download the latest release and use your favorite ESP8266 flashing tool to flash the following:

• boot_v1.3(b3).bin to 0x00000
• blank.bin to 0x7e000
• user1.bin to 0x01000

Note that the firmware assumes a 512KB flash chip, which most of the esp-01 thru esp-11 modules appear to have. A larger flash chip should work but has not been tested.

Wifi configuration overview

For proper operation the end state the esp-link needs to arrive at is to have it join your pre-existing wifi network as a pure station. However, in order to get there the esp-link will start out as an access point and you'll have to join its network to configure it. The short version is:

1. the esp-link creates a wifi access point with an SSID of the form ESP_012ABC
2. you join your laptop to the esp-link's network as a station and you configure the esp-link wifi with your network info by pointing your browser at http://192.168.4.1/
3. the esp-link starts to connect to your network while continuing to also be an access point ("AP+STA"), the esp-link may show up with the esp-link.local hostname (depends on your DHCP/DNS config)
4. the esp-link succeeds in connecting and shuts down its own access point after 15 seconds,