Intergas Central Heating Monitor for Homie 2.0

This is an update of the previous Intergas Central Heating Monitor. The functionality is almost the same but it is much faster (due to the asynchronuous communication) and the source code is much more simple because of Homie. The software is monitoring my Intergas Prestige CW6 without any issues for more than a year now.

• This program can read the the status of a Central heating from Intergas. It has been built for an esp8266. The central heating status is sent through MQTT to a central system (MQTT broker).

• Configuration is done using the configuration mode Homie. No need to add wifi password to the code anymore.

• How to connect the esp8266 to the Intergas (is the same as previous version)

  I have included a diagram how to connect the optocouplers (and a picture of the prototype): https://github.com/keesma/Intergas-Central-Heating-Monitor-Homie/blob/master/Intergas%20reader%20optocoupler.jpg

  To connect the central heating to the esp8266. It is best to use an optocoupler to connect the esp8266 to the Intergas. E.g. an 4n25 can be used (take two 4n25s to protect both tx and rx). I got good results by using a 220 Ohm resistor for the input and a 1k Ohm resistor in the output.

  Default config on the esp8266 is:

  • pin 4: Rx
  • pin 5: Tx
  • pin 12: LED. The LED is on during initialization and while sending data to the Intergas. The communication speed is 9600 baud.

  The intergas has a 4 pin plug with: Vcc, ground, Tx and Rx.

  I power my esp8266 with a HiLink 3.3V power supply. With this power supply it is rock solid (previous power supply had reset issues).

• Dependencies

  • Homie 2.0: [https://github.com/marvinroger/homie-esp8266] (Homie is working very well)

• Openhab: I have connected the esp8266 through MQTT to openhab. Openhab can display the data, save it and create nice graphs. The item definitions are included. The rules are required for translating the status bytes to (bit) values. https://github.com/keesma/Intergas-Central-Heating-Monitor-Homie/tree/master/openhab

• Time: the time is no longer synchronised with an NTP server. Homie has a timer that counts how many seconds it has been running since the last reset.

• Power: My esp8266 has a separate 3.3V power supply. The Intergas may supply power but prefer not the experiment with that (it only supplies power to one of the optocouplers).

• Changes compared to previous version (without Homie):

  • No ntp time synchronisation (uptime is still there)
  • The status description is no longer created by the firmware (is done in rule in openhab)
  • Two status bytes became one status word
  • Most important status bits are determined in the firmware (opentherm, pump running)
  • Two external temperature sensors can be added (flow & return)

  Note: not all bits have been extracted from the status word to prevent too much communication.