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Home Assistant MQTT

This repository now includes a small helper that pushes Kamstrup meter data to a Home Assistant MQTT broker using the pykmp-tool equivalent API calls.

Install on Raspberry Pi

  1. Create a virtualenv on the Pi (or reuse your existing one) and install the extras needed for the CLI and MQTT publishing:

    $ python3 -m venv /opt/pykmp/.venv
$ source /opt/pykmp/.venv/bin/activate
$ pip install --upgrade pip
$ pip install ".[tool]" paho-mqtt

  2. Copy the example environment file and fill in the MQTT and serial settings:

    $ sudo cp contrib/systemd/pykmp-ha.env.example /etc/pykmp-ha.env
$ sudoedit /etc/pykmp-ha.env

    The defaults request registers 60 68 80 74 86 87 266 every 300 seconds (5 minutes) from /dev/ttyUSB0. Set MQTT_HOST to your broker address; leave MQTT_DISCOVERY=true to let Home Assistant auto-discover the sensors.

  3. Install the systemd unit and point it at your checkout/venv:

    $ sudo cp contrib/systemd/pykmp-ha-mqtt.service /etc/systemd/system/
$ sudoedit /etc/systemd/system/pykmp-ha-mqtt.service

    Update User/Group, WorkingDirectory and ExecStart if your paths differ, for example:

    WorkingDirectory=/opt/PyKMP
ExecStart=/opt/pykmp/.venv/bin/python /opt/PyKMP/examples/home_assistant_mqtt.py

  4. Enable and start the service:

    $ sudo systemctl daemon-reload
$ sudo systemctl enable --now pykmp-ha-mqtt.service
$ sudo systemctl status pykmp-ha-mqtt.service

Make sure the chosen User is allowed to talk to the meter (e.g. a member of the dialout group when using /dev/ttyUSB0).

What gets published

  • Serial number once on startup: <MQTT_BASE_TOPIC>/serial
  • All registers together: <MQTT_BASE_TOPIC>/state
    • Per-register states (JSON, retained): <MQTT_BASE_TOPIC>/register/<id>
    • MQTT discovery (when MQTT_DISCOVERY=true): homeassistant/sensor/pykmp_<serial>_<id>/config

The state payload now includes both a compact map and a register_data list that mirrors pykmp-tool get-register --json, for example:

{
  "serial": "123456",
  "timestamp": "2024-04-12T12:00:00Z",
  "register_data": [
    {
      "id_int": 60,
      "id_hex": "0x003C",
      "name": "Heat Energy (E1)",
      "device_class": "energy",
      "state_class": "total_increasing",
      "unit_of_measurement": "kWh",
      "unit_int": 2,
      "unit_hex": "0x02",
      "unit_str": "kWh",
      "value_float": 135152.0,
      "value_str": "135152"
    }
  ]
}

MQTT discovery payloads now also include device_class and state_class when the unit is recognized (e.g., energy, power, temperature, volume, flow). For flow the script now converts l/h to m³/h so Home Assistant accepts the unit; raw values and units are still included alongside the converted values.

Home Assistant will create one sensor per register via the discovery payloads. If you prefer manual sensors, point them at the per-register topics above.