Tag Archives: mqtt

Control a StorkAir/Zehnder WHR 930 ventilation unit using mqtt

Our house is equipped with a WHR 930 ventilation system, in Dutch a ‘warmte terugwin systeem (wtw)’ and since we have the ‘basic’ version, we have to control it using switch in the bathroom. There is a RF module available for the WHR 930, but that’s a pretty expensive option and i could not figure out how open it was. Since i want to control it from Home Assistant, it must be open or should have some sort of API.

Searching the internet for possibilities i learned that the WHR 930 has a serial interface on it’s mainboard and that the protocol is fully reverse engineered! The picture below is one of the mainboard, the red arrow points at the serial interface (RJ45)

I modified a UTP cable to get the right pin layout for a Serial<>USB converter and attached it to a Raspberry Pi and wrote some python code to interface with the WHR 930 via the serial connection. The code reads the various temperature values and fan status and publishes the results on a mqtt topic. The python code subscribes to a specific mqtt topic (house/2/attic/wtw/set_ventilation_level) for messages (0, 1, 2 or 3) to set the ventilation level. Level 0 stops the ventilation, i did not even know that the WHR 930 could do that 🙂

For now i am happy, but the serial protocol description shows that there is much more possible. Maybe i will look into that later, but do not hesitate to contact me (see my Github page for contact info) if you found out nice additions!

For integration with Home Assistant, see the README file on my Github channel.

Push Hue switch status on a MQTT topic

Since a few weeks we have a Hue switch which can be used to set the Hue lights on and off and also dim or brighten them. Of course the Hue switch only triggers Hue devices and nothing else. But i wanted to trigger other devices also, like a wifi tp-link switch that’s connected to a normal light  when someone pushes the ‘on’ button. And when the ‘off’ button is pressed, all lights in the livingroom should go off, but also that light that’s connected to the tp-link switch and even the TV, radio and the tp-link switch that switches a few devices behind the tv-set that’s not needed at night.

Sadly the switch does not have a webhook or something like that, but it is possible to get the state of the switch from the Hue bridge. With a simple curl command. we can get the state of our switch (our’s has id 2): curl -s -XGET http://<ip address>/api/<user>/sensors/2

 "state": {
 "buttonevent": 1002,
 "lastupdated": "2017-01-22T11:34:05"
 "config": {
 "on": true,
 "battery": 100,
 "reachable": true,
 "pending": []
 "name": "Hue switch",
 "type": "ZLLSwitch",
 "modelid": "RWL021",
 "manufacturername": "Philips",
 "swversion": "",
 "uniqueid": "00:aa:bb:cc:00:ff:00:ff-00-ff00"

Now it is pretty simple to poll the Hue bridge and when someone pushes a button, send the id of the button on a MQTT topic. I use Home Assistant to catch that event and trigger an action depending on the button pressed. Btw, button 1 is ‘on’, button 2 is ‘brighten, button 3 is dim and button 4 is off.

# -*- coding: utf-8 -*-

import time
import json
import requests
import mosquitto

######## CONFIG ########
urlhuebase = "http://<ip address>/api/<user>"
port = 8123
use_ssl = True
sensorid = '2'
pollingtime = 1

def publish_message(msg, mqtt_path):
  mqttc.publish(mqtt_path, msg, 1)

def SensorState(sensorid):
  urlhue = urlhuebase + "/sensors/" + sensorid
  hueresponse = requests.get(urlhue)
  state = hueresponse.json().get('state')
  data = [ state['buttonevent'], state['lastupdated'] ]
  return data

# Connect to the MQTT broker
mqttc = mosquitto.Mosquitto("publish_hue_switch")

sensordata = SensorState(sensorid)
lastupdated = sensordata[1]
print "lastupdated: {0}".format(lastupdated)

while True:
    sensordata = SensorState(sensorid)

    if (sensordata[1] != lastupdated):
      button = str(sensordata[0])[0:1]
      publish_message(msg=button, mqtt_path='house/0/hallway/hueswitch/button_pressed')
      print 'Button pressed: {0}'.format(button)
  except KeyboardInterrupt:
    print 'Exiting on request'