There is a really nice, simple and cheap solution to connect a bathroom body (fat) scale to openHAB (vs. going through the intended cloud services): At least in Germany, Medisana body fat scales (such as the models BS410, BS430, BS440, BS444) are partially sold for ~20 €. They can easily be connected to openHAB via a neat python script (BS440). It is based on this project which started some years back. Because of that, some of the steps are different compared to the one listed on the wordpress blog. If I missed something, let me know.
The following step-by-step instruction below works for me without any problem on my Hardware-setting (Raspberry 3B+, internal Bluetooth Adapter) with openHAB 3.4 (installed on Docker according to this step-by-step instruction). Software-prerequisites are mentioned below. The script offers multiple plugins for further data processing, however, I followed the “MQTT-path” to get the data to openHAB.
1) Connect the scale
- Log into your Raspi. Switch on Bluetooth LE on the Raspi via
sudo btmgmt le on - Start scanning for Bluetooth Devices with
sudo hcitool lescan. When you step on the scale (it turns itself on), a new device should appear. Write down both the MAC address as well as the device name. When in doubt, repeat the “stepping on the scale”-part to make sure you’re looking at the right device. - Test the connectivity (make sure the scale is switched on) with
gatttool -b xx:xx:xx:xx:xx:xx -I(put in your MAC address) and Enter, followed byconnect. You should now see the message “Connection successful” - Avoid having to use super user privileges (sudo) on hcitool by
sudo setcap 'cap_net_raw,cap_net_admin+eip' `which hcitool` - Avoid having to use super user privileges (sudo) on btmgmt by
sudo setcap 'cap_net_raw,cap_net_admin+eip' `which btmgmt` - Check if python3 is already installed (typing in
pythonleads to e.g.Python 3.9.2 (default, Mar 12 2021, 04:06:34). - Install pip (python package manager) by typing in
sudo apt-get install python3-pip. - Install Pygatt (Python Module for Bluetootn LE) by
sudo pip install "Pygatt[GATTTOOL]" - Install Paho MQTT (enables applications to connect to an MQTT broker to publish messages) so that the results can be sent via MQTT to openHAB by typing in
sudo pip3 install paho-mqtt - Install git (open source distributed version control system) to be able to download and install the BS440 script automatically from Github by typing
sudo apt-get install git. - Download and install the BS440 script by typing in
git clone https://github.com/keptenkurk/BS440.git - Change to the directory of the downloaded script by
cd BS440and rename the .ini file from BS440.example.ini to BS440.ini by typing inmv BS440.example.ini BS440.ini - Open and edit the .ini file with
nano BS440.iniand insert the following information:ble_address,device_name(as noted before) andevice_model. Uncomment the plugins-line and only include the plugins which you need (here: MQTT), so that it looks like this:
Save and close withCtrl + X→Y→Enter. - Run the program with
python BS440.py - To test if everything is working correctly, step on the scale. You should see something like this. Note that the immediate result is just the weight, and only after ~25 seconds the complete dataset (incl. height, muscle, etc) is transmitted for the previous 30 measurements.
2023-01-12 20:25:54,183 INFO <module> Configured plugins: BS440mqtt
2023-01-12 20:sudo setcap 'cap_net_raw,cap_net_admin+eip' `which btmgmt`25:54,184 INFO <module> Loading plugin: BS440mqtt
2023-01-12 20:25:54,453 INFO <module> All plugins loaded.
2023-01-12 20:25:54,453 INFO <module> BS440 Started
2023-01-12 20:25:54,545 INFO init_ble_mode b'hci0 Set Low Energy complete, settings: powered ssp br/edr le secure-conn \n'
2023-01-12 20:26:07,360 INFO <module> Continue Comms: True
2023-01-12 20:26:07,642 INFO <module> Waiting for notifications for another 30 seconds
2023-01-12 20:26:07,647 INFO processIndication {'valid': True, 'person': 255, 'gender': 'male', 'age': 0, 'size': 0, 'activity': 'normal'}
2023-01-12 20:26:37,678 INFO <module> Could not disconnect...
2023-01-12 20:26:37,679 INFO <module> Done receiving data from scale
2023-01-12 20:26:37,680 ERROR <module> Unreliable data received. Unable to process
2023-01-12 20:26:50,121 INFO <module> Continue Comms: True
2023-01-12 20:26:50,407 INFO <module> Waiting for notifications for another 30 seconds
2023-01-12 20:26:50,410 INFO processIndication {'valid': True, 'person': 2, 'gender': 'male', 'age': xx, 'size': xx, 'activity': 'xx'}
2023-01-12 20:26:50,437 INFO processIndication {'valid': True, 'weight': xx, 'timestamp': 1673117954, 'person': 2}
2023-01-12 20:26:50,457 INFO processIndication {'valid': True, 'timestamp': 1673117954, 'person': 2, 'kcal': xx, 'fat': xx, 'tbw': xx, 'muscle': xx, 'bone': xx}
2023-01-12 20:26:50,477 INFO processIndication {'valid': True, 'weight': xx, 'timestamp': 1673124836, 'person': 2}
2023-01-12 20:26:50,497 INFO processIndication {'valid': True, 'timestamp': 1673124836, 'person': 2, 'kcal': xx, 'fat': xx, 'tbw': xx, 'muscle': xx, 'bone': xx}
2023-01-12 20:26:50,517 INFO processIndication {'valid': True, 'weight': xx, 'timestamp': 1673125002, 'person': 2}
...
2) Configure MQTT
The next steps bring the data via MQTT to openHAB.
- Change to the plugins-folder via
cd pluginsand rename the .ini config file of the MQTT plugin from BS440qmtt.example.ini to BS440qmtt.ini viamv BS440mqtt.example.ini BS440mqtt.ini. - Open and edit the BS440mqtt.ini file with
nano BS440mqtt.iniand insert the following information:client_id(pick anything you want),hostname(the IP address of your openHAB server,localhostif the BS440-script is run on the same Raspi),port(1883 for the setting according to the Docker stack),usernameandpasswortfrom mosquitto (also see here for the Docker-stack instruction). Leaveha-auto-discoveryatTrueto allow for automatic mqtt scanning in openHAB later on, and define the names of the people registered at the scale, e.g. like this:
Save and close withCtrl + X→Y→Enter. - If still running, quit the program (Ctrl + X) and run the program again with
python BS440.py. Note that the program has to be running to work.
3) Add thing and channels in openHAB
Since Auto-Discovery was activated in the BS440.ini-file, adding a thing and channels in openHAB is pretty straight forward:
- Go to Settings → Things → + → mqtt.
- An entry should show up already (prerequisite: the person must have stepped on the scale before and data has had to be transmitted already. Don’t be confused about the “homeassistant”-topic: The MQTT-extension was developed by our friends from the HA-community.
4) Start the script when the Raspbian is started
For the script to constantly monitor the scale, it ideally has to be started during startup of the system as a service.
- In Terminal, go to the subfolder of the script
/dist/init/linux-systemdviacd ~/BS440/dist/init/linux-systemd. In this folder open the service-file withnano bs440.service. - Edit/verify the WorkingDirectory (the absolute path where the script’s files are stored, probably
/home/pi/BS440if the instruction above has been followed), the python directory (usually/usr/bin/python) as well as the name of the script (defaultBS440.py). To make sure that paho mqtt is loaded when the script is started, setAfter=multi-user.target.
Save and close with Ctrl + X → Y → Enter.
3. Copy the service-file from /home/pi/BS440/dist/init/linux-systemd/bs440.service to /etc/systemd/system via sudo cp /home/pi/BS440/dist/init/linux-systemd/bs440.service /etc/systemd/system/.
4. Tell SystemD to detect new service files via systemctl daemon-reload.
5. Start the service systemctl start bs440.
6. Set the service to start at boot via systemctl enable bs440.
Once you’re done and have done a reboot via sudo reboot, you can check the logs of the new bs440 service via journalctl -l -f -u bs440.
Closing remarks:
- As visible in the original repository on Github, there are some bugs open. Some of them are in the process of being fixed, some are not. The original project also got somehow abandoned, with someone from the HA-community having picked up the threads. Let’s see how things go.
- Bluetooth LE is for good reasons limited to a distance of only couple of meters. Hence, the openHAB-server might be too far away to reach the scale. There have been thoughts on running the code on an ESP (which would be neat), but what’s probably easier to pull off is just a Raspi Zero acting as a relais (though this only works with some workaround due to the inability to have Wifi and BT LE being active at the same time, see here).
