sml2mqtt

sml2mqtt

sml2mqtt is a Go-based command line tool that reads SML (Smart Message Language) data from a file or device, extracts specific sensor values, and publishes them to an MQTT broker. This tool can be useful for monitoring energy meters or other devices that use the SML format.

Features

• Read SML data from a file or device
• Supports multiple sensor values and extracts them based on user-defined criteria
• Publish extracted sensor values to an MQTT broker and allows to auto discover them by home assistant

Prerequisites

• Go (version 1.16 or higher)
• MQTT broker (e.g., Mosquitto)

Installation

1. Clone this repository:

git clone https://github.com/mfmayer/sml2mqtt.git

1. Change to the project directory:

cd sml2mqtt

1. Build the binary:

go build -o sml2mqtt

1. Move the binary to your desired location (optional):

sudo mv sml2mqtt /usr/local/bin/

Usage

sml2mqtt [options]

Reads file and published specified values to given broker.

Options:

• -file <path>: Path to the file with sensor values.
• -broker <url>: URL to the MQTT broker.
• -value <sensorValue>: Value's OBIS code, ValueName, DeviceClass, UnitOfMeasure and optional CorrectionFactor. Format: ObisCode,ValueName,DeviceClass,UnitOfMeasure[,CorrectionFactor] (e.g., "1.0.1.8.0,Energy,energy,kWh[,0.001]"). Multiple sensor values can be specified.

Example

sml2mqtt -file /path/to/sml/file -broker mqtt://localhost:1883 -value "1.0.1.8.0,Energy,energy,kWh,0.001"

Serial Device Files

When you want to read the SML from a serial device file, ensure to appropriately configure the serial device beforehand. For example the following command configures the serial interface /dev/ttyUSB0 with the following settings: 9600 baud rate, 8 data bits, 1 stop bit, no parity checking, and in raw mode.:

sudo stty -F /dev/ttyUSB0 9600 cs8 -cstopb -parenb raw

UDEV Rules

When you want to read the SML from multiple serial device files (e.g. multiple UART USB devices), it might be helpful to name dem specifally based on the USB port they're plugged in.

To find specific information that you want to use in UDEV configurations you can use the command udevadm info -a -n /dev/ttyUSB0

To e.g. find the USB port the device is plugged in execute: udevadm info -a -n /dev/ttyUSB0 | grep devpath (or idProduct for the product ID)

So exemplary UDEV rules for two serial devices to read out electricity meters could be (/etc/udev/rules.d/99-usb-serial.rules):

SUBSYSTEM=="tty", ATTRS{idVendor}=="1a86", ATTRS{idProduct}=="7523", ATTRS{devpath}=="1.2", SYMLINK+="emeter0"

SUBSYSTEM=="tty", ATTRS{idVendor}=="1a86", ATTRS{idProduct}=="7523", ATTRS{devpath}=="1.3", SYMLINK+="emeter1"

SystemD Service

In order to create a SystemD service you freate a SystemD service file

sudo nano /etc/systemd/system/sml2mqtt_emeter0.service

with the following content:

[Unit]
Description=SML to MQTT Service
After=network.target

[Service]
Type=simple
User=sml2mqtt
WorkingDirectory=/var/lib/sml2mqtt
ExecStartPre=/usr/bin/stty -F /dev/emeter0 9600 cs8 -cstopb -parenb raw
ExecStart=/usr/local/bin/sml2mqtt --file /dev/emeter0 --broker tcp://horst:1883 --value 1.0.1.8.0,Energy,energy,kWh,0.001 --value 1.0.16.7.0,Power,power,W
Restart=always
RestartSec=5

[Install]
WantedBy=multi-user.target

This will read out enery (OBIS 1-1:1.8.0) and power (OBIS 1-0:16.7.0) from /dev/emeter0 and provide it to give MQTT broker with the topics:

• homeassistant/sensor/emeter0_Energy/config - to register the entity with home assistant
• homeassistant/sensor/emeter0_Energy/state - to publish/update the value

The config topic is only published at startup and then from time to time every few minutes.

After creating the service file, don't forget to update the systemd configuration by reloading its deamon:

sudo systemctl daemon-reload

And finally start and enable the service (if it shall be restarted after reboot)

sudo systemctl start sml2mqtt_emeter0
sudo systemctl enable sml2mqtt_emeter0

License

This project is released under the MIT License. See the LICENSE file for details.