Modbus

Installation Instructions

The Modbus com interface need the libmodbus library to work. Follow the steps below to set up your environment before compiling FORTE.

1. libmodbus files should be placed in the following folder structure:
   • [ibmodbushome]/include/modbus: include files
   • [libmodbushome]/lib: libmodbus.lib (windows) or libmodbus.so (posix)
2. When configuring FORTE project with CMake choose [ibmodbushome] as FORTE_COM_MODBUS_LIB_DIR
3. forte.exe must be able to find the dynamic libmodbus library after build. Therefore copy libmodbus.dll/so to folder with forte.exe or add libmodbus.dll/so to library include path.

Parameters

Modbus Client (TCP)

Usage of the Modbus Client (TCP):

• protocol: tcp (tcp is default)
• ip: address of Modbus server, e.g. 127.0.0.1
• port: preferably above 1024, default is 502
• pollFrequency: polling frequency in milliseconds
• functionCode: an integer between 1 and 4
  • 1 = Read Coils
  • 2 = Read Discrete Inputs
  • 3 = Read Holding Registers
  • 4 = Read Input Register
• slaveId (optional): the slave id used by the modbus server (0xFF is standard); this is in principle an optional parameter but some modbus devices - e.g. Siemens SENTRON PAC power measurement devices - need this parameter in order to establish a connection
• readAddresses: addresses can be specified between 0-65535 more than one address (max 100) can be specified using
  • comma for separate addresses 0,2,65500
  • dots for interval 5..10
  • combination 0,5..10,2,65500
• sendAddresses: addresses can be specified between 0-65535 if data is only read sendAddresses should be left empty more than one address (max 100) can be specified using
  • comma for separate addresses 0,2,65500
  • dots for interval 5..10
  • combination 0,5..10,2,65500
• responseTimeout (optional): timeout in milliseconds to wait for a response (500ms is default)
• byteTimeout (optional): timeout in milliseconds between two consecutive bytes (500ms is default)

Example:

Modbus Client (RTU)

Usage of the Modbus Client (RTU):

Parameter meaning:

• protocol: rtu
• device: serial device, e.g., /dev/ttyS0
• baudRate: baud rate
• parity: N for none, E for even, O for odd
• dataBit: number of data bits
• stopBit: number of stop bits
• pollFrequency: polling frequency in milliseconds
• functionCode: an integer between 1 and 4, whereas
  • 1 = Read Coils
  • 2 = Read Discrete Inputs
  • 3 = Read Holding Registers
  • 4 = Read Input Register
• slaveId (optional): the slave id used by the modbus server (0xFF is standard); this is in principle an optional parameter but some modbus devices - e.g. Siemens SENTRON PAC power measurement devices - need this parameter in order to establish a connection
• readAddresses: addresses can be specified between 0-65535. More than one address (max 100) can be specified using
  • comma for separate addresses 0,2,65500
  • dots for interval 5..10
  • combination 0,5..10,2,65500
• sendAddresses: addresses can be specified between 0-65535. More than one address (max 100) can be specified using
  • comma for separate addresses 0,2,65500
  • dots for interval 5..10
  • combination 0,5..10,2,65500
• responseTimeout (optional): timeout in milliseconds to wait for a response (500ms is default)
• byteTimeout (optional): timeout in milliseconds between two consecutive bytes (500ms is default)

Example:

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