sml2ha - SML Smart Meter to Home Assistant via MQTT

A native Rust implementation of the Smart Message Language (SML) protocol is provided to integrate smart meters (electronic household meters) into Home Assistant via MQTT Discovery.

The gap between modern electronic meters (with optical D0 interfaces) and home automation is bridged by this project. SML data frames are read from a serial port (e.g., via a USB-IR read head) and telemetry is published to Home Assistant. Robust frame synchronization and decoding are ensured by the use of the sml_rs library.

Manufacturer and model information is automatically decoded from the SML Server ID (FNN standard), ensuring that devices are correctly identified within Home Assistant. Supported manufacturers include EBZ, EMH, EasyMeter, APA, and Logarex.

This project, including this README, was completely written with AI assistance (Gemini Flash/Pro). No manual code review has been performed. The status is marked as WorksForMe 😀

A YAML configuration file (config.yml) is utilized by the application:

serial:
  port: "/dev/ttyUSB0"     # Path to the IR read head
  baud_rate: 9600          # Usually 9600 for SML

mqtt:
  host: "localhost"        # MQTT Broker address
  port: 1883               # MQTT Broker port
  client_id: "sml2ha"      # Unique client ID
  topic_prefix: "sml2ha"   # Prefix for MQTT topics
  send_cycle_sec: 5        # Optional: Update interval in seconds (default: as fast as possible)

logging:
  debug: true              # Verbose console output is enabled

MQTT Discovery is leveraged by this application, meaning the smart meter is automatically detected by Home Assistant as a new device once the application is initiated. The unique ID for each sensor is prefixed with the meter's serial number to prevent naming conflicts.

The following sensors are automatically registered:

• Energy Import Total: 1.8.0 counter (kWh)
• Energy Export Total: 2.8.0 counter (kWh)
• Power Current Total: 16.7.0 current total power (W)

A clean device page is created in Home Assistant by the integration, where the telemetry data such as Energy Import Total, Energy Export Total and Power Current Total are shown.

For a great overview of the energy flow, the use of the Power Flow Card Plus is recommended.

The following configuration can be used to integrate the Power Flow Card Plus with the smart meter (the serial number 12345678901234567890 should be replaced with the actual smartmeters serial number):

type: custom:power-flow-card-plus
entities:
  grid:
    entity: sensor.sml_12345678901234567890_power_current_total
  solar:
    entity: sensor.sma_1234567890_pac

sml2ha can be executed as a Docker container.

docker build -t sml2ha .

The serial device must be mapped into the container.

services:
  sml2ha:
    image: sml2ha:latest
    restart: unless-stopped
    devices:
      - "/dev/ttyUSB_easymeter:/dev/ttyUSB_easymeter"
    volumes:
      - "./config.yml:/app/config.yml:ro"

Issues can be opened or pull requests can be submitted. If time allows, they will be reviewed.

Thanks to everybody who contributed to a part that is used by this project or was used to develop it.

This project is licensed under the MIT License.