Adding Modbus Devices - viewLinc 5.1

Vaisala viewLinc Enterprise Server version 5.1 User Guide

Document code
viewLinc 5.1
Content type
Product description
Product description > Features
Reference information
Document type
User guide

viewLinc can be configured to retrieve data from both Vaisala and non-Vaisala Modbus-enabled measurement devices containing a maximum of 8 channels per device. Vaisala Modbus devices can be connected to a viewLinc Device Host as part of your standard viewLinc license, while third-party/non-Vaisala Modbus devices require the purchase and addition of a Modbus license.
To see the current number of licensed Modbus devices or available viewLinc device spaces, see Help > About.
Several of Vaisala's measurement devices and other manufacturer's devices use the Modbus communications protocol. The associated device documentation provides important details you will need to configure a Modbus TCP or Modbus RTU device in viewLinc.

Connecting Modbus Devices

Modbus RTU devices may be connected to your network with a Digi or other Ethernet device, or with a serial cable to connect directly to a viewLinc Device Host. Modbus TCP devices are connected directly to your network with a network cable.

Connecting Modbus devices to your network requires advanced networking expertise. Refer to your Modbus device documentation to complete the installation steps, including installation of required Digi or Ethernet device drivers on the host server, and verification of network connectivity.

Input and Holding Registers

Modbus devices contain input and holding registers that read and write data using 16-bit or 32-bit wide integers. The data structure used by the Modbus device manufacturer defines the way you will need to configure viewLinc.

The first step is to refer to your Modbus device documentation to determine whether the register format is based on an address (decimal or hexadecimal) or a number. If your device uses the wider 32-bit format, the data format may be higher byte/word first or lower byte/word first.

Register Types Register Number Ranges Data format options
Coil 00001-09999 Boolean / Boolean Inverted
Discrete Input 10001-19999 Boolean / Boolean Inverted
Input Register 30001-39999
  • 16-bit Integer / Unsigned Integer
  • 16-bit Boolean / Boolean Inverted
Holding Register 40001-49999
  • 32-bit Integer, Little-endian / Little-endian, word swapped
  • 32-bit Integer Big-endian / Big-endian word swapped
  • 32-bit Unsigned Integer, Little-endian / Little-endian, word swapped
  • 32-bit Unsigned Integer Big-endian / Big-endian word swapped
  • 32-bit Float Little-endian / Little-endian word swapped
  • 32-bit Float Big-endian / Big-endian word swapped
  • 32-bit Boolean / Boolean Inverted
Additional Modbus reference information about mapping registers can be found online, such as
Since Modbus device documentation is not standardized, it may provide configuration information in a variety of ways. To learn more about Modbus, useful online resources include:, and 'How to add a Modbus Device', available from the Tours menu.