Modbus TCP Master

Driver that creates a Modbus TCP master (client) to communicate with ModBus TCP slaves (servers). The Modbus protocol exchanges information using a request-reply mechanism between a master (client) and a slave (server). The master-slave principle is a model for a communication protocol in which one device (the master) controls one or more other devices (the slaves).

Uses the library pyModbusTCP.

Register Numbers	Type	Address	Name	Data Type	Value Range
1-9999	Read-Write	%IX	Status/Coil (State controls)	bool	0 or 1
10001-19999	Read-Only	%QX	Input Contact (State information)	bool	0 or 1
30001-39999	Read-Only	%QW	Input Registers (Numerical values)	uint, word	0 to 32767
40001-49999	Read-Write	%IW	Holding Registers (Numerical values)	uint, word	0 to 32767

Parameters

Aside from the common parameters described in the communication_driver docs, this driver includes:

Parameter	Default Value	Description
host	'127.0.0.1'	The slave IP address
port	502	The slave port to connect to

Setup data

The setup data will give values to the parameters required and will specify the I/O variables info.

{
  "parameters": {
    "host": "127.0.0.1",
    "port": 502
  },
  "variables": {
    "1": {
      "datatype": "bool",
      "size": 1,
      "operation": "write"
    },
    "10001": {
      "datatype": "bool",
      "size": 1,
      "operation": "read"
    },
    "30001": {
      "datatype": "word",
      "size": 1,
      "operation": "read"
    },
    "40001": {
      "datatype": "word",
      "size": 1,
      "operation": "write"
    }
  }
}

tip

In most cases we recommend using the %QW and %IW addresses (registers 30000 -> 49999) even when dealing with boolean variables, since this allows sending the information of 16 booleans using a single register.

note

The setup_params in the generic PLC components for modbustcp_master will need the following format:

{ "host": "127.0.0.1", "port": 502 }