Making Modbus device communicate with a PC


Thread Starter


I am learning more about MODBUS, and I would like to know how I make the Modbus device communicate with the PC. Like for example, how do I gather outputs/inputs from Modbus? Do I need to do some programming?? Or do I need to make an interface board so that the Modbus device and the PC can communicate? Anyone can help? Please...
No interface board needed.

There are two separate thing to consider: physical connection and Modbus software.

First => physical conntection. Modbus devices communicates via serial connections for Ethernet connections.

If your Modbus device have Ethernet port, then connect both your PC and the device to the same network hub or switch using Cat5 cables. You can even use a crossover Cat 5 to connect your PC to the Modbus device.

If your Modbus device have a RS232 port. This normally have a DB9 port. If the device is consider a Data Communication Equipment (DCE) then you can connect using a standard straight-thru cable. If it is a DTE device, then use a null modem cable. A null modem cable is used to connect two DTE devices. Your PC is always a DTE device.

If the device is have a serial RJ45, the you can use either a DB9-RJ45 converter or a RJ45 breakout adapter to facilitate the connection. RJ45 serial pinouts varies from manufacturer to manufacturer, so you will need to consult the manufacturer for the pinout.

There is also pinout database on the web at

As for software, there are many PC-based softwares out there that can be used to talk to a Modbus device. You can Google:"modbus+simulator"

Some of the vendors will give you a 30-day trial period.

Hope this helps. Email me with specifics and I can help more.

Tom.Tran @ Industran. com
Depends on type of Modbus.

Modbus TCP - generally Ethernet over TCP/IP.

Modbus RTU - generally serial port, but can be embedded in Ethernet.

Modbus ASCII - generally serial port, but can be embedded in Ethernet or wireless.

Modbus Plus - Requires expansion card or module.

Visit for a complete line of Modbus driver solutions for Windows PCs.

Fully functioning 30-day trial versions of all software are available for download.

Ready-to-run example applications will have you communicating within minutes.

Fred Loveless

Kepware's Modbus driver Suite in it Enhnanced OPC Server KepserverEx will get you connected to almost all the Modbus enabled devices out there. it supports OPC, DDE, FastDDE/SuiteLink, and NIO PDB for client connectivity.


Fred Loveless
Support Manager
Kepware Technologies
I have very good experiences with ModSim32 and ModScan32. You can find them on the web and it is definately possible for "free", if you want it to be. ModSim32 used for simulate registers of a slave over either ModBus TCP or RS485. ModScan32 is used as the opposite (master) as it polls the registers from a ModBus slave.

Completely priceless software for commissioning and testing engineers. Simple and stupid and always works = the way it should be :D


Steven Smethurst

You can write your own software to read Modbus points, it's pretty simple. All you have to do is read the API.

The people above have already told you how to connect your Modbus device to your computer.

When it comes time to test your device, I suggest that you use a tool like Modbus Scanner

Deepak Bhopatkar

I am a newbie to Modscan32 scripting. Since you are an experienced user, request help. can you send me some working Modscan32 Script Sample, especially one which includes multiple register read with response verification of register content. It would help me as reference to write my own scripts. Thanks in advance.

Deepak Bhoopatkar
As others have said it depends very much on the type of Modbus. If you have programming experience and are looking for the cheapest solution, there is a free Java driver for Modbus called "jamod." I have successfully implemented about 10 projects using it to create a PC control/monitoring system for Modbus devices. It works either on TCP/IP and serial RS232 (RTU and ASCII). If you are interested, I wrote a blog article about it here:

Feel free to contact me if you decide to go this route.

Jon Carson
DMC Inc.
Expert Software + Engineering Services
> <

I am very much interested in getting my Square D PowerLogic Circuit Monitors that use Modbus to talk directly to my PC. But I could not get your link below to work. Could you advise/correct the link?
Thank you

Robert J. Honders CE
Honderosa Valley Consulting & Renewables Research
Studio Building I
129 Kennel Rd.
Cuddebackville NY 12729

Honders [at] HVC.RR.COM
Robert [at]
Phone: 845 754 7106
If you are using Modbus/TCP, I have a Python driver. See ""

There are three packages. The MBLogic package is a complete soft logic platform. The MBTools package has a number of stand alone programs for web based HMI, a Modbus/TCP server, a GUI based program for reading and writing arbitrary Modbus/TCP addresses (for testing and troubleshooting) and a few other things as well. The MBLibs package provides the Modbus/TCP client protocol as a library, together with a demo and documentation on how to use it to write your own programs.

i am new to the modbus communication. Basically what my application is that we are taking field data through modbus scanner in ifix5.0. Right now i don't have the scanner hardware and i want to send some data through simulation. I have downloaded both modscan32 and modsim32 but i am not able to communicate with these softwares. If anybody can help me out. you can also e-mail the solution.

Naveen Kumar

I find your solution easily applicable. In my case the requirement is to gather data from devices that support MODBUS RTU protocol and display it on a PC or display.The device has both RS 485 and RS 232 ports for serial communication. I need a software for acquiring data into PC and would like to know how to display this data. In future I want to extend this feature to issue commands from pc to the devices using a HMI. Any suggestion shall be highly
ICC has recently released a free Modbus master program (works with Modbus serial and TCP). It's different from programs like Modscan etc. in that it allows you to define an XML "profile" of the registers that exist on a device. You can then upload/download/compare parameter sets (i.e. for device backup/restore/cloning operations) or continuously log parameter sets to a CSV file, which can then easily be manipulated/graphed via Excel, etc. It runs on the .NET platform in Windows.
The Port40 Automation Management Server will provide you WS-Management web services, JSON, and XML interfaces for not only Modbus, but BACnet, OPC, and a number of other industrial standards as well. Visit for details.