MODBUS communication issue

Question

Hi,

I am currently working on establishing MODBUS TCP communication between a Typhoon HIL hardware (configured as a client) and a MODBUS device (configured as a server). Below is a summary of the setup:

• Client IP (Typhoon HIL): 169.254.154.72
• Server IP (MODBUS device): 169.254.154.70
• Server Port: 502
• Slave ID: 1
• Function Code: Read Holding Registers
• Read Address: Address of register in Modbus device
• Number of Registers to Read: 2
• Transmit Period: 1000 ms

In the simulation, I am sending an analog voltage from the HIL hardware’s analog output to the MODBUS device’s analog input. The MODBUS device correctly displays the analog voltage on its display, confirming that the signal is being received.

However, when attempting to read the same value back via MODBUS into Typhoon SCADA, the value returned is consistently 0. The MODBUS client reports:

• Exception Code: 0 (no error)
• State: 1 (communication active)

Despite this, the expected analog value is not being received. All configuration parameters have been verified, and multiple test cases have been attempted (including reading nearby registers and using different function codes), but the issue persists.

I would appreciate any insights or suggestions you may have to help resolve this.

Answer 1

Can you read your modbus server device using some other client?

Are you using TyphoonSim software?

Comments

Yes, I can read with Modscan tool

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What version of THCC software are you using? Can you connect THCC modbus client to PC Modscan tool? Can you change server slave id to 255 and try that? If your regsiter is in range 40001+ can you try to put 0+ in Typhoon Client? Are HIL, PC and Modbus server all on the same router?

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I am currently using version V2025.2 THCC. I am unable to establish a connection between the Typhoon HIL client and the PC ModScan tool. All devices — the HIL system, PC, and Modbus server — are connected to the same router.

Answer 2

Hello, what is the IP address of the HIL device you are using?

Answer 3

Hello, I've tried to reproduce the issue you are facing on a simple model that contains a Modbus Client with settings you provided. In this model, values are set on two SCADA Inputs, and read on the Modbus Server tool, while input values (sent from Modbus Server tool) are read on the output probes of Modbus Client. 

Connection was established between pyModSlave tool and Typhoon HIL Modbus Client, and it is possible to both read values on the Modbus Client outputs and receive the sent values on Modbus Device.

Were you able to resolve this issue? Can you please share more details about your model and setup? What HIL device are you using? Is it connected to PC using USB or ethernet cable? Is this the only request on the Modbus Client you set? Are the register addresses overlapping any other addresses on the Modbus Client or Modbus Device? Are there any warnings or errors raised on the Modbus Device you are using?