Connecting multiple CooLinkHub to a single Modbus RTU line

This article applies to the following CoolAutomation  products:

  • CooLinkHub


Connecting multiple clusters of CooLinkHub & wireless CoolPlugs  into a single Modbus RTU line requires changing the default configuration and connecting the CooLinkHubs as slaves.





  • Download the CoolAutomation Toolbox or using any other terminal SW (Putty, built-in windows terminal SW, etc.…)
  • Network access to the network that the device is connected to (via local TCP/IP connection) or USB Type A to Type B for local network interface enablement (USB cable supplied with CooLinkHub).
  • A computer with a network or USB connection

Configuration steps

The steps below should be applied of all of the CooLinkHubs you would like to connect to the Modbus RTU line.


Setting CooLinkHub line for CG (Cool Gate)

  • >line type L3 CG5

    OK, Boot Required!
  • Boot 2


Setting Modbus ID (changing from default)

  • >line myid L3 51
    OK, Boot Required!
  • Boot 2


Setting Modbus format parameters (Baud rate, parity bit etc...)

This is an optional step


The default Modbus format is:

Baud Rate 9600 bps

Data Bits 8

Parity None

To change Modbus format follow these steps:

  • >line baud L3 19200_8N2
    OK, Boot Required!
  • boot 2


Setting VA (Virtual Addresses)


VA - Virtual Addressing is a representation of each IDU (VRF or Split) on the internal Modbus register table of network Coolautomation device

Normally VA are distributed after identification of IDU on network devices screen. In the case of CoolPlug & CooLinkHub layout, each IDU is represented by CoolPlug, so the VA auto distribution command must be applied after all wireless CoolPlugs are paired with respective CooLinkHub and powered. (Can be pre-set before onsite installation).

When CoolPlugs are installed onsite, they are powered from the AC, but during laboratory pre-set, they can be powered via a direct USB connection to CooLinkHub. The paring process is described in the "How to Pair a Wireless CoolPlug to a CooLinkHub" video tutorial and CoolPlug installation manual 


Distributing  VA’s

>VA auto


querying the VA’s

L1.100 --> 0001 [Hex: 0x0011 | Dec: 00017]
L1.101 --> 0002 [Hex: 0x0021 | Dec: 00033]

For a complete set of the Modbus commands, please refer to the full Modbus guideline

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