LabVIEW Modbus Protocol for Serial Communications

[markus36]

Hello everyone,

I am trying to create a LabVIEW vi using Modbus protocol to pull data from a CryoMech compressor (from COM2 using an RS-485 connection, user manual is attached). The wires are then connected to an EVC8024 USB to Serial Converter (using COMN3 for the RS-485). The code I've created so far allows me to send commands to the compressor (such as the start and stop command). But I am unable to pull data from the compressor with the Modbus protocol. When I try to pull data via the Modus protocol, I only get one element and its value isn't anything that I would be expecting. I'm not sure why.

CryoMech also provided a Python file for pulling data from the compressor via Modbus protocol in case anyone needs more detail on how the data is pulled from the compressor.

This is my first time using LabVIEW's Modbus protocol and posting on a LabVIEW forum, so please be patient with me. 

[RIObotics · Accepted solution]

Hi there,

With all things being equal, have you tried the use the python script?  If it doesn't work, then you know that it's not a LabVIEW problem, but a general RS-485 modbus problem.  If it works, then you'll have a working reference.  Just make sure you are executing the actions in LabVIEW as in the python script, and you should be good.

BR

John

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[markus36]

From what I've seen with the RS-485 to USB converter it seems like there might be an issue with the hardware. It's not a software problem as the Python script also had trouble with getting a status from the compressor. Thanks for your help, John.