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I have had a CurrentCost Power sampling device on my house electrical supply for a few years, since I got it free switching providers. It came with a panel that allows you to view the momentary values for power consumption, but in these days of data aggregation and IoT, this is as close to useless as it gets. I already have a HomeAssistant server runniing on a Docker Host I use for such things, and I have a few other IoT-friendly devices lying around, so I thought I would try to integrate these to gather and display historical power consumption for my home.

Data collection with rtl_433

I have a few RTLSDR devices, and the CurrentCost unit transmits metrics on 433MHz ISM, so teh first step is to configure a device that will gather this data over RF. Since I plan to use this as a sort of RF gathering hub, I will use a spare Pi3b and one of the RTLSDR devices.

I installed a fresh Rasbian Buster and configured a static network lease. Once this was done, I installed rtl-sdr and rtl_433, as follows:

 $ sudo apt install rtl-sdr
 $ sudo apt-get install libtool libusb-1.0.0-dev librtlsdr-dev
 $ sudo apt-get install git git-core cmake libusb-1.0-0-dev
 $ git clone https://github.com/merbanan/rtl_433.git
 $ cd rtl_433/ && mkdir build && cd build && cmake ../ && make
 $ sudo make install

Containerised MQTT

Once I had a working install of rtl_433, the next step was to setup an MQTT broker to pass messages between the client (rtl_433) and HomeAssistant. HomeAssitant does have an MQTT broker module, but the Docker install does not include the Supervisor and Add-Ons functionality, so deploying a Containerised solution is more in keeping with the modular ideology that is in vogue today. The Docker host I use for this stuff uses Docker Compose to manage the deployment and configuration of Docker images, so I added the following to docker-compose.yml:

# Mosquitto - MQTT Broker
  mosquitto:
    image: eclipse-mosquitto
    hostname: mosquitto
    container_name: mosquitto
    expose:
      - "1883"
      - "9001"
    ports:
      - "1883:1883"
      - "9001:9001"
    volumes:
      - ${USERDIR}/docker/mosquitto/config:/mosquitto/config
      - ${USERDIR}/docker/mosquitto/logs:/mosquitto/logs
      - ${USERDIR}/docker/mosquitto/data:/mosquitto/data
    networks:
      - default

I then brought the container up with docker-compose up -d and my MQTT broker was active. The next step was to configure HomeAssitant to listen to the MQTT broker for messages. This is done by entering the Configuration section, and selecting Integrations and clicking the orange + to add an integration. Find MQTT, and enable. Then enter the details for the MQTT broker and it’s all done. Well almost…

Configuring HomeAssistant

The nest step is to configure HomeAssistant to listen for a Topic and to make data from this topic avaialble as a variable for use in the UI. The following snippet should be added to configuration.yml:

sensor:
  - platform: mqtt
    state_topic: "CurrentCost/Power/power0_W"
    name: "CurrentCost_Power"
    unit_of_measurement: "Wh"
    device_class: power

This listens for anything posted on the Topic CurrentCost/Power/power0_W, and assigns it the variable name CurrentCost_Power. It also assigns a device class of ‘power’ so that HomeAssistant will know what icons to use for the variable. Where does this Topic come from? The configuration of rtl_433 comes next.

Configuring rtl_433 to post Topics

rtl_433 can output data it reads in many formats. The default is as a formatted table to stdout, i.e. the screen. However, for our purposes, the pretty-formatting is superfluous. It can also do JSON, CSV and other machine-readable formats, and, of most interest to us, it can connect directly to an MQTT broker and post Topics. To do this, we create a configuration file for rtl_433. If a file is created in one of a few specific locations, rtl_433 will automatically load it and use it to configure itself. In this instance, we will create the file at /etc/rtl_433/rtl_433.cfg

frequency     433.92M
report_meta time:iso
report_meta protocol
output mqtt://192.168.1.105:1883,retain=0,devices=CurrentCost/Power
stop_after_successful_events false
protocol 44  # CurrentCost Current Sensor

This configures rtl_433 to listen on 433.920MHz ISM band for Protocol 25 devices (CC Sensor) and output the data to an MQTT broker using the TopicCurrentCost/Power. It will send multiple parameters, which can be seen by using Developer Tools -> MQTT in HomeAssistant and selecting the Topic CurrentCost/Power/#, but power0_W is the one we are interested in.

Once we have rtl_433 configured, we configure systemd to maintain it, as follows - create a Unit file in /etc/systemd/system/rtl_433-mqtt.service

[Unit]
Description=rtl_433 to MQTT publisher
After=network.target
[Service]
ExecStart=/usr/local/bin/rtl_433
Restart=always
RestartSec=5
[Install]
WantedBy=multi-user.target

Once created, we can start & enable the service as follows:

$ sudo systemctl enable rtl_433-mqtt.service
$ sudo systemctl start rtl_433-mqtt.service