the modbus integration in home assistant

[alexandrecuer]

This is about how to use the modbus integration in home-assistant : https://www.home-assistant.io/integrations/modbus/

in devcontainer in RTU mode

tested with a modbus usb dongle and some promux modules :

• a very cheap USB dongle
• a PM4RO with 4 relays
• a PMDAIO, which combines 2 RTD , 2 AI, 1 AO, 4 DI and 2 DO

adapt your devcontainer.json so that runArgs map the dongle as a device in the container : "runArgs": ["--device=/dev/ttyUSB0"]

rebuild the container

the home assistant devcontainer runs under the vscode user

whoami
vscode

add the user vscode to sudoers : sudo usermod -a -G dialout,tty,sudo vscode

exit vscode, restart the container through portainer and restart vscode

modify your configuration.yaml

modbus:
  - name: modbus_hub
    type: serial
    port: /dev/ttyUSB0
    baudrate: 9600
    bytesize: 8
    method: rtu
    parity: N
    stopbits: 1
    switches:
      - name: modbus_switch_1
        slave: 1
        address: 0x0000
        write_type: coil
        command_on: 0x01
        command_off: 0x00
        scan_interval: 10
    sensors:
      - name: promux_daio_RTD1
        slave: 0
        address: 3
        input_type: holding
        unit_of_measurement: °C
        precision: 1
        scale: 0.1
        scan_interval: 10
        unique_id: pmdaioRTD1

then restart home assistant : python3 -m homeassistant -c ./config

You can pilot through the dashboard

you can pilot through automations

what is inside these automations ?

example with the start_heating automation

GUI	yaml

trigger: time
at: "12:30:00"
weekday:
  - mon
  - tue
  - wed
  - thu
  - fri

action: switch.turn_on
metadata: {}
data: {}
target:
  entity_id: switch.modbus_switch_1

[alexandrecuer]

in TCP mode

using a modbus TCP simulator in a dedicated container :

modbustcpserver_raw.py code for a dedicated tcp server :

"""basic modbus tcp server with pymodbus."""

import asyncio
import argparse
import logging

from pymodbus.server import StartAsyncTcpServer
from pymodbus.datastore import (
    ModbusSequentialDataBlock,
    ModbusServerContext,
    ModbusSlaveContext,
)

FORMAT = "%(asctime)-15s %(levelname)-8s %(module)-15s:%(lineno)-8s %(message)s"
logging.basicConfig(format=FORMAT)
_logger = logging.getLogger()


def setup_server(args):
    """Initial server setup."""
    datablock_coils = ModbusSequentialDataBlock(0x00, [0] * 100)
    datablock = ModbusSequentialDataBlock(0x00, [17] * 100)
    context = ModbusSlaveContext(
        di=datablock_coils, co=datablock_coils, hr=datablock, ir=datablock
    )
    # single=True => every device id returns the same context.
    args.context = ModbusServerContext(slaves=context, single=True)
    return args


async def run_updating_server(args):
    """Start updater task and async server."""
    context = args.context
    address = ("", args.server_port)
    await StartAsyncTcpServer(context=context, address=address)


levelchoices = ["critical", "error", "warning", "info", "debug"]

if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "--level", help=",".join(levelchoices), default="info", type=str
    )
    parser.add_argument("--server_port", type=int, default=5020)
    cmd_args = parser.parse_args()
    _logger.setLevel(cmd_args.level.upper())
    run_args = setup_server(cmd_args)
    asyncio.run(run_updating_server(run_args), debug=True)

Note that after pymodbus 3.11.0, ModbusSlaveContext has been renamed to ModbusDeviceContext

mount the folder containing modbustcpserver_raw.py

configuration.yaml :

modbus:
  - name: "modbustcp"
    type: tcp
    host: 172.17.0.3
    port: 502
    sensors:
      - name: modbustcp_1_40007
        slave: 1
        address: 6
        input_type: holding
        state_class: measurement
        scan_interval: 60
        precision: 1
        scale: 1
        data_type: int16
      - name: modbustcp_1_40006
        slave: 1
        address: 5
        input_type: holding
        state_class: measurement
        scan_interval: 60
        precision: 1
        scale: 1
        data_type: int16

Use an automation to write on a holding register as the modbus integration integrates a modbus.write_register service (action was previously called something like service call in home-assistant)

On the dashboard

Before the write	After