Communicating with a modbus serial device via the com port

[BSCeet]

I have a PLC contoller that is outputting modbus protocol data via serial cable. I am able to read the holding registers with modscan but unable to communicatie with the device with LabVIEW in any way. If anyone has information on how to do so or any VI's that will be able to help, it would be greatly appreciated. Im a senior in college and in need of this information for a project. Thanks.

[unclebump]

Start with the NI modbus library.

https://forums.ni.com/t5/Reference-Design-Content/LabVIEW-Modbus-API/ta-p/3524019

Or download portmon and use it to watch the data as modscan is working. Then use VISA and serial port commands to transfer data bytes until it matches what modscan is transmitting. You'll learn more doing it this way.

Also download the modbus protocol pdf file.

https://forums.ni.com/t5/LabVIEW/Howto-choose-modbus-tcp-functions-with-dsc-8-0-1-DSC-register/m-p/3...

Message Edited by unclebump on 03-10-2008 06:04 PM