Connect Paradox COMBUS (green-yellow wires which connect alarm system to the keypad) alarm interface to Home Assistant using esp8266 device and ESPHome library.
Currently the implementation is read-only, it shows motion, window/door, smoke sensor and alarm state status in Home Assistant (with a slight delay).
Because Combus operates at ~12v, we need to step down voltage to levels suitable for esp2866.
Wiring example:
Alarm Aux(+) --- Voltage regulator (5v for Wemos, NodeMCU, 3.3V for generic esp8266) --- VIN pin on esp8266
Alarm Aux(-) --- esp8266 Ground
+--- clock pin (Wemos, NodeMCU: D1, D2, D8)
Alarm Yellow --- 15k ohm resistor ---|
+--- 10k ohm resistor --- Ground
+--- data read pin (Wemos, NodeMCU: D1, D2, D8)
Alarm Green ---- 15k ohm resistor ---|
+--- 10k ohm resistor --- Ground
When using different pins, be sure to modify sources to match your configuration.
In order to make OTA updates, connection switch in frontend must be switched to OFF.
Tested with "Trikdis SP231" alarm system which uses Paradox-compatible green-yellow data bus (COMBUS). Should work with other Paradox alarm systems.
- Most of the code is taken from https://github.com/liaan/paradox_esp8266
- Wiring and some ideas taken from https://github.com/taligentx/dscKeybusInterface
- General knowledge about decoding COMBUS and a source for future improvements https://github.com/0ki/paradox
- ESPHome library https://esphome.io
This is a rough implementation, stability is not guaranteed. If you want a stable solution with read/write capability and your alarm system is compatible, take a look at Paradox Alarm Interface, which connects to alarm system by using serial port. In my case my alarm system was not compatible and had to use my own solution.