PC server, ModbusRTU/TCP, load cells and barcode/RFID readers


Thread Starter

Bo Nystedt

I have got a project where a pc server(Windows 2000 Server) has to communicate (Modbus RTU and Modbus TCP protocols) with 50 load cells/scales and 50 barcode scanners over the RS232, RS485 and Ethernet interfaces.

Each loadcell/scale has its own barcode scanner and they are supposed to work in sync, which means the scanner should read the barcode label belonging the the item on the corresponding scale and report the results to the server. I am a C# VS2005 programmer and have no experience of Modbus protocols. How do I keep my job? My wife and the children have already left. They even took the canary bird with them!
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Nathan Boeger

I'm not much help in writing Modbus directly with .NET. The way that I'd recommend to deal with this situation with commercial software would be cheap and easy to set up. First you'd get Modbus RTU and TCP OPC servers (I'd recommend Kepware) to communicate with the scales and barcode scanners. You would then use FactorySQL to sync the OPC source (devices) to any SQL database (via an ODBC connection). This would be pretty quick and easy to set up. You would then do whatever custom .NET programming you need to via the SQL database. It would be done with polling, but can work fine at a rapid (subsecond) rate. This may not work for you if you need much faster device status indication. I would recommend downloading free trials and testing it yourself. You can call Inductive Automation or post to their forums to help you get started.


Good luck with the family. I'm sorry about the Canary ;)

Nathan Boeger
Inductive Automation
"Design Simplicity Cures Engineered Complexity"

Ganesh Okade


Checkout this link for a C# .NET implementation of the MODBUS Master and Slave protocols. This can help you in getting MODBUS out faster on your system. What these libraries provide are basically C# .NET class libraries which can be imported into your own application. You can then make calls to the member functions exported by them.


Ganesh Okade
Sunlux Technologies Ltd.


I've used a tool from a company called Focus Software, out of Australia. The product is Field Talk, and it comes in many versions for many O/S. You also have a choice of master or slave libraries.

Check them out at http://www.focus-sw.com
and for heaven's sake, keep your priorities in order will ya? We all could get group rates on divorce lawyers in this business if we're not careful! :)