Using Modbus RTU Relay with Homeassistant

Preparation

Hardware Preparation

Raspberry Pi: https://www.waveshare.com/product/raspberry-pi/boards-kits/raspberry-pi-4/pi4b-starter-kit.htm
Modbus RTU Relay 16CH: https://www.waveshare.com/modbus-rtu-relay-16ch.htm
RS485 CAN HAT: https://www.waveshare.com/rs485-can-hat.htm
Raspberry Pi 4 USB-C Power Supply: https://www.waveshare.com/rs485-can-hat.htm
Power Supply 5V: https://www.waveshare.com/psu-5v-4a-5.5-2.1-us.htm
【Optional】USB TO RS485: https://www.waveshare.com/usb-to-rs485.htm

1. Install Raspberry Pi OS System

Download Raspberry Pi OS: https://www.raspberrypi.com/software/operating-systems/#raspberry-pi-os-64-bit

After installation, the Raspberry Pi OS system environment is as follows:

2. Install Home Assistant Core

Install Home Assistant Core, See the tutorial: Raspberry Pi - Home Assistant (home-assistant.io) (This tutorial installs version 2024.3.0)

After installation, open the browser and run Home Assistant:

3. Environment Configuration

Hardware connection diagram:

On the Raspberry Pi, configure RS485 CAN HAT, refer to: https://www.waveshare.com/wiki/RS485_CAN_HAT#RS485_Usage

Execute the following command to enter the Raspberry Pi configuration:

sudo raspi-config

Choose Interfacing Options -> Serial -> No -> Yes:
You need to disable the login shell and enable the serial port hardware:

Configure Homeassistant's configuration.yaml on Raspberry Pi, file path: /home/homeassistant/.homeassistant/configuration.yaml

sudo nano /home/homeassistant/.homeassistant/configuration.yaml

Add the following content at the end of the file:

modbus:
  - name: modbus_hub
    type: serial
    port: /dev/ttyS0
    baudrate: 9600
    bytesize: 8
    method: rtu
    parity: N
    stopbits: 1
    binary_sensors:
      - name: my_relay
        address: 0
        device_class: plug
        input_type: coil
        scan_interval: 15
        slave: 1
        slave_count: 15
        unique_id: my_relay
    lights:
      - name: "Light_1"
        address: 0
        write_type: coil
        slave: 1
      - name: "Light_2"
        address: 1
        write_type: coil
        slave: 1
      - name: "Light_3"
        address: 2
        write_type: coil
        slave: 1
      - name: "Light_4"
        address: 3
        write_type: coil
        slave: 1
      - name: "Light_5"
        address: 4
        write_type: coil
        slave: 1
      - name: "Light_6"
        address: 5
        write_type: coil
        slave: 1
      - name: "Light_7"
        address: 6
        write_type: coil
        slave: 1
      - name: "Light_8"
        address: 7
        write_type: coil
        slave: 1
      - name: "Light_9"
        address: 8
        write_type: coil
        slave: 1
      - name: "Light_10"
        address: 9
        write_type: coil
        slave: 1
      - name: "Light_11"
        address: 10
        write_type: coil
        slave: 1
      - name: "Light_12"
        address: 11
        write_type: coil
        slave: 1
      - name: "Light_13"
        address: 12
        write_type: coil
        slave: 1
      - name: "Light_14"
        address: 13
        write_type: coil
        slave: 1
      - name: "Light_15"
        address: 14
        write_type: coil
        slave: 1
      - name: "Light_16"
        address: 15
        write_type: coil
        slave: 1

Then save and exit.

Configuration.yaml download link：https://files.waveshare.com/wiki/Modbus%20RTU%20Relay/configuration.yaml
After the configuration is complete, restart the Raspberry Pi and re-run Homeassistant:

Please see the video for actual measurement results:
- See the video of the test: https://files.waveshare.com/wiki/Modbus%20RTU%20Relay/Modbus-Relay-Homeassistant-Test-Video.mp4
- Turn on all Relay.

Turn on Relay 1~4, 9~12:

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