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RI-RTUTCP

RI-RTUTCP is protocol converter between Modbus RTU and Modbus TCP

Operation modes

Modbus RTU

Conveter can be used to allow Master with RS-485 port to interface with Modbus TCP devices.

sequenceDiagram
  autonumber
  box RS-485
    participant Master
    participant Converter as RI-RTUTCP
  end
  participant Remote as TCP Device
  Master->>Converter: Request to TCP Device
  activate Master
  activate Converter
  Note over Master,Converter: Modbus RTU over RS-485
  Converter->>Remote: Request to TCP Device
  activate Remote
  Note over Converter,Remote: Modbus TCP over Ethernet
  Remote->>Converter: Response from TCP Device
  Note over Converter,Remote: Modbus TCP over Ethernet
  deactivate Remote
  Converter->>Master: Response from TCP Device
  Note over Master,Converter: Modbus RTU over RS-485
  deactivate Converter
  deactivate Master

Other devices

This mode allows multiple devices on RS-485 bus to be connected alongside RI-RTUTCP.

sequenceDiagram
    autonumber
    participant Master
    participant Local as RTU Device
    participant Converter as RI-RTUTCP
    par
        activate Master
        Master->>Local: Request to RTU Device
        activate Local
        Note over Master,Local: Modbus RTU over RS-485
    and
        Master->>Converter: Request to RTU Device
        activate Converter
        Note over Master,Converter: Modbus RTU over RS-485
    end
    rect
    break
        Converter-->>Converter: Requested TCP Device not found
    end
    end
    deactivate Converter
    Local->>Master: Response from RTU Device
    Note over Master,Local: Modbus RTU over RS-485
    deactivate Local
    deactivate Master

Modbus TCP

Conveter can be used to allow Modbus TCP master to interface with Modbus RTU end-devices.

sequenceDiagram
  autonumber
  participant Master
  box RS-485
    participant Converter as RI-RTUTCP
    participant Remote as RTU Device
  end
  Master->>Converter: Request to RTU Device
  activate Master
  activate Converter
  Note over Master,Converter: Modbus TCP over Ethernet
  Converter->>Remote: Request to RTU Device
  activate Remote
  Note over Converter,Remote: Modbus RTU over RS-485
  Remote->>Converter: Response from RTU Device
  Note over Converter,Remote: Modbus RTU over RS-485
  deactivate Remote
  Converter->>Master: Response from RTU Device
  Note over Master,Converter: Modbus TCP over Ethernet
  deactivate Converter
  deactivate Master

Autodiscovery

When connecting two or more RS-485 networks over Ethernet using multiple RI-RTUTCP it is possible to:

  • use DHCP in Ethernet network
  • leave TCP address and Port configuration to RI-RTUTCP autodiscovery feature

effectively achieving zero configuration setup.

sequenceDiagram
  autonumber
  box Local RS-485
    participant Master
    participant Converter as RI-RTUTCP
  end
  box Remote RS-485
    participant ConverterSlave as RI-RTUTCP
    participant Remote as RTU Device
  end
  Master->>Converter: Request to RTU Device
  activate Master
  activate Converter
  Note over Master,Converter: Modbus RTU over RS-485
  opt
    Converter-->>ConverterSlave: Autodiscovery Request
    Note over Converter,ConverterSlave: UDP Broadcast
    ConverterSlave-->>Converter: Autodiscovery Response
    Note over Converter,ConverterSlave: UDP Unicast
  end
  Converter->>ConverterSlave: Request to RTU Device
  activate ConverterSlave
  Note over Converter,ConverterSlave: Modbus TCP over Ethernet
  ConverterSlave->>Remote: Request to RTU Device
  activate Remote
  Note over ConverterSlave,Remote: Modbus RTU over RS-485
  Remote->>ConverterSlave: Response from RTU Device
  Note over ConverterSlave,Remote: Modbus RTU over RS-485
  deactivate Remote
  ConverterSlave->>Converter: Response from RTU Device
  Note over Converter,ConverterSlave: Modbus TCP over Ethernet
  deactivate ConverterSlave
  Converter->>Master: Response from RTU Device
  Note over Master,Converter: Modbus RTU over RS-485
  deactivate Converter
  deactivate Master