This device can send "door open" command to intercom main unit after receiving of incoming call. It only works with coordinate line intercoms. Tested with Cyfral russian intercom.

Thanks to Metori for original progect

• NodeMCU v3 x 1
• Double relay module x1 (or two single relay modules)
• LED x3 (or one RGB LED)
• Button x2
• Optocoupler x1
• Some resistors

1. Оптопара PC817B
2. Реле электромеханическое 2-канальное
3. NodeMCU V3
4. RGB светодиод на плате
5. Кнопка тактовая 6х6х13мм KFC-A06-13H
6. Провода "мама-мама" 10см, 20 шт.
7. Провода "папа-мама" 10см, 20 шт.
8. Резисторы
9. microUSB кабель

Thanks to Oleg Yu

1. Fill in WiFi and MQTT credentials in software.h
2. Fill in upload_port in platformio.ini
3. Use PlatformIO to build and upload firmware

• 'R' - ready; sent after successfull boot-up or after receiving of 'P' message
• 'L' - last will message; send when device goes offline

• 'O' - door open command
• 'N' - call reject command (door will not open)
• 'P' - ping command (answers with 'R')

• 'C' - call; sent after detecting of incoming intercom call
• 'H' - hangup; sent after detected incoming call finished
• 'B' - button; sent when "door open" has been performed by green hw button press
• 'J' - reJected; sent when incoming call has been rejected by red hw button press
• 'S' - success; sent in response to 'O' or 'N' command
• 'F' - fail; sent in response to 'O' or 'N' command (this means that 'O' or 'N' command has been received but no incoming call detected)

Full configuration with sensor, switches and automations

Put this file into /config/packages/domofon.yaml and correct notification service in automations.