Friday, December 18, 2020

OpenHAB vs Xiaomi Sensor

original from 

Some time ago I started to use OpenHAB to expand the monitoring of my servers to the whole apartment. It would be nice to know whether I closed the freezer in the basement again or if I left the door open out of sheer senility. Corresponding sensors are available for relatively little money, e.g. from Xiaomi (or from other manufacturers for a lot more money, whether they are easier to integrate is the big question). However, the integration of the Xiaomi sensors in OpenHAB is a Chinese opera in several acts: 

 Act 1: The starter set The starter set is available for around 80.- and it comes with a pressure switch, two door sensors and two motion detectors as well as the base station. According to the description, everything is very simple: Start the base station, install the Mihome app on an Android phone, select "Mainland China" as the server location, connect the app to the base station, activate developer mode via a hidden menu, read out the key and so that the base station can be integrated into OpenHAB. Then everything would be very easy with a data flow sensor -> Xiaomi Hub -> OpenHAB. Yes but... Exactly, because the whole thing only works with the "Mainland China Edition" base station, which is not available in Europe. You can presumably have them delivered overseas through a Chinese wholesaler (don't forget the travel adapter, Chinese plugs don't fit into European sockets). But the EU edition is unusable: - If you select "Mainland China" as the server location in the app, the base station cannot be found and therefore cannot be connected - If you choose the server location "Europe", the hidden menu to activate the developer mode is missing. 

 Act 2: Obsolete app With a little research it turned out that an outdated version of the Mihome app can be found on dubious pages, which contains an error: It writes a debug log. Where to find the access key. Unfortunately, that alone doesn't help. This allows you to integrate the hub via the Xiaomi Mi IO extension from OpenHAB. But that was all. As a result, there is still no access to the sensors. For this, the developer mode would still have to be activated, which also opens Telnet access on the device. Now there are two more options: A modified Mihome app from a Russian website that is completely in Cyrillic. Well uh ... Njet! Or unpack the soldering iron, tap the serial port, use it to gain terminal access and activate the Telnet server. Now that there is a good chance that this can destroy the device, I prefer to leave it (for now). At least I could resell it while it still works. 

 Act 3: The Aqara Hub A further look at the documentation of the Mihome binding shows: The hub in version 3 (which is available as Aqara Hub for Apple Homekit) should be a little more accessible. Unfortunately, that costs almost as much as the whole set. And then just as little can. I immediately sent it back accordingly ...

Act 4: Cheap Zigbee Stick
The Xiaomi devices, like all proprietary garbage, of course never exactly adhere to the standards. But at least enough that the protocol just barely passes as Zigbee. So I bought a USB Zigbee stick from the richest man in the world for € 9 + € 3.50 shipping. To my great surprise, this, although electronic device, it was sent from amazon germany to switzerland. Very unusual. And arrived super fast too. Also unusual.

It is a simple USB stick with a CC2531 chip and zigbee2mqtt-compatible firmware preinstalled. Very awesome!

In principle, OpenHAB would be able to address the Zigbee stick directly via the Zigbee binding. The data flow would then be Sensor -> USB stick -> OpenHAB. But there was something with the protocol standard at Xiaomi and stick to it. The sensors can be integrated, but are displayed as "offline" and no status can be queried. As usual, the following applies: why easy when it can be complicated?

Now the from-behind-through-the-chest-in-the-eye installation for the data flow sensor -> USB stick -> zigbee2mqtt -> mqtt-broker -> OpenHAB begins.
First the stick is connected, it is recognized as a USB serial device / dev / ttyACM0.
Now an MQTT broker has to be installed, e.g. mosquitto from the Debian package sources. This is started without further configuration.
Next, zigbee2mqtt is installed with what feels like two thousand Node.JS dependencies (including npm from the Debian backports if you use Debian Stable as a base). In contrast to the OpenHAB part that follows later, this is excellently documented, so that this part feels more like paint-by-numbers than system administration.

In principle, the devices can now be integrated. Simply reset the sensor with the SIM pin included in the package, and that's it. According to the instructions, you may have to repeat the process several times, but with the first two sensors it worked right away. A look at journalctl -u zigbee2mqtt -f shows activity.

Now comes the hard part: connecting OpenHAB to MQTT. This is documented very superficially and abstractly. Add to this the chaos with instructions for MQTT1 and MQTT2 binding when you google for solutions. Which now applies to my installation? Boh? Ultimately, I followed the instructions for MQTT2, and that worked at some point. Probably: MQTT1 == OpenHAB1, MQTT2 == OpenHAB2 (and I'm running 2.5).

How to proceed:
In the zigbee2mqtt configuration file /opt/zigbee2mqtt/data/configuration.yaml, the output should not be output as JSON but as an attribute. To do this, insert the following lines, save, restart zigbee2mqtt:

    output: attribute

And if we are already fiddling with the configuration, one should also assign sensible friendly_name to the sensors.
First install the MQTT binding in OpenHAB.
Then create a .things file with the required entries in /etc/openhab2/things /. At some point I found halfway suitable instructions in the forum ...
And now you are surprised that the things appear in the GUI, but no data is read ... Signal strength? NaN. Battery level? NaN. Status? Off. grrrmpf. After a long debugging process (yes, zigbee2mqtt writes in mosquitto, you can read along with mosquitto_sub -v -t '#') at some point just triggered the spontaneous Windows reflex and restarted OpenHAB itself. Aaand! Bingo! Everything works. So easy! Incidentally, the restart is necessary for every newly added (or renamed) device.

The finale: the OpenHAB Things file

Bridge mqtt:broker:MosquittoMqttBroker "Mosquitto MQTT Broker" [ host="", secure=false] {
Thing topic xdoor1 "Xiaomi Door Sensor" @ "Location" {
Type switch : contact "contact" [ stateTopic = "zigbee2mqtt/xdoor1/contact", on="true", off="false" ]
Type number : voltage "voltage" [ stateTopic = "zigbee2mqtt/xdoor1/voltage" ]
Type number : battery "battery" [ stateTopic = "zigbee2mqtt/xdoor1/battery" ]
Type number : linkquality "linkquality" [ stateTopic = "zigbee2mqtt/xdoor1/linkquality" ]

Additional sensors can now easily be added to the bridge block. With a little more typing, sensors can also be defined outside the bridge block:

Thing mqtt:topic:MosquittoMqttBroker:BodySensor "Xiaomi Body Sensor" (mqtt:broker:MosquittoMqttBroker) @ "Location" {
Type switch : occupancy "occupancy" [ stateTopic = "zigbee2mqtt/xbody1/occupancy", on="true", off="false" ]
Type number : voltage "voltage" [ stateTopic = "zigbee2mqtt/xbody1/voltage" ]
Type number : battery "battery" [ stateTopic = "zigbee2mqtt/xbody1/battery" ]
Type number : linkquality "linkquality" [ stateTopic = "zigbee2mqtt/xbody1/linkquality" ]

The existing channels can be found out via mosquitto_sub or journalctl. As soon as you stimulate a sensor, it sends all of this information to the Zigbee controller.

Of course, especially in combination with Zigbee (or Z-Wave), OpenHAB is a bottomless pit in terms of possibilities. A lot of technology can be connected even without a wireless connection: printers, mail and XMPP accounts, WLAN (or connected devices), telephone systems, mpd (Music Player Daemon), video cameras (e.g. via Zoneminder - but that would be a blog entry in itself) . With Zigbee everything gets even wilder. After the sensors, the entire rest of the house can be integrated, from lamps, heating and roller shutter control to the washing machine to the lawn mower to the wallbox of the electric vehicle.
If more Zigbee sensors / actuators are to be set up a little further away, you simply take a Raspberry Pi, connect another USB stick to it, install zigbee2mqtt and have the sensor data sent over the network to the MQTT broker on the OpenHAB machine .

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