Connecting Mitsubishi and CODESYS PLCs to the Cloud (Modbus Focus)

In this course, we’ll show how to use Modbus RTU/TCP to link Mitsubishi PLCs and CODESYS projects to your IoT gateway.

Requirements

• Raspberry Pi or PC with Python 3.7+, Docker, and Node-RED.
• Mitsubishi PLC with Modbus RTU or TCP support.
• CODESYS project exported with Modbus communication.
• Python libraries: pymodbus, paho-mqtt.

Modbus Configuration

• For RTU: configure serial port (/dev/ttyUSB0) and parameters (baud rate, parity).
• For TCP: IP address, port 502, and unit ID.
• In CODESYS, add a Modbus Master or Slave channel depending on the role.

Examples in Python

from pymodbus.client.sync import ModbusSerialClient, ModbusTcpClient
from paho.mqtt.client import Client

# Initialize clients
rtu = ModbusSerialClient(method='rtu', port='/dev/ttyUSB0', baudrate=9600)
tcp = ModbusTcpClient('192.168.0.20')
mqtt = Client()
mqtt.connect('broker.local')

# Read Holding Registers
rr = tcp.read_holding_registers(100, 4, unit=1)
print(rr.registers)
# Publish to MQTT
mqtt.publish('plant/mitsubishi/data', rr.registers)

Node-RED Flows

1. Install Modbus RTU/TCP and MQTT nodes.
2. Configure the PLC connection (serial or TCP).
3. Design a flow that:
   • Reads registers and publishes them to MQTT topics.
   • Receives MQTT commands and writes them to the PLC.

Practical Project

• Develop a service that monitors multiple PLCs and consolidates data in InfluxDB.
• Create Grafana dashboards for real-time visualization.