Periodically losing serial communications - LabVIEW 8.5/DSC module

[MReveley]

Christian

The NI Spy log I sent you was the same one that had the error at line# 30375. As far as the read error is concerned, I am actually not using VISA read directly. I am using an I/O modbus server in the LabVIEW DSC module and shared variables in my VIs to do my serial communications. Is there something I should be doing to modify the server?

Matt

[mbtoday]

This is what I ran into using the DSC 8.5.1 modbus server.  The module is not designed for more than one Modbus device on a serial port.  When I spawned 15 of the servers to communicate with my devices on one port, they were all "in synch" on their polling rate and corrupting their data just as this person is reporting.  I worked around the problem temporarily by programmatically setting the "polling rate" on each Modbus server module to different values such as 1.3 seconds, 1.7, etc. so that it would be rare that two would attempt simultaneous bus usage.

My ultimate solution will be to ditch the DSC Modbus express VI and write my own multiple-modbus-slave routines using the older LabView Modbus library so I can poll at will.

I've told my sales rep that this is NI shooting itself in the foot - advertising a Modbus server but not stating up front that it is a "limited functionality" Modbus server.  How many people only have ONE Modbus slave on an RS-485 line for example?  A few, I'm sure, but a definite minority.

I hope this is the issue that you are facing and that this workaround "works" for you.

Mike

[CCM]

Hi mbtoday,

     Actually I also face the same problem as describe in this post. After running the application for certain moment, the error message will pop out and I have to restart my PC in order to run the LabView again. Seems like you have found the momentary solution by changing the polling time for different modbus. May I know where can I change the polling time? By the way what is the best communication settings that I should use (Baud rate, Refresh rate, Retry attempts, Wait if fails, and so on.

     Honestly, I'm just a beginne in using LabView. Hope you can help me. Thanks in advance!

[bozo69]

Hello Guys, I have the same issue.

I use DSC 2009 with modbus master & slave on Ethernet and 2 master modbus on serial.

This error is very rare but I need to reboot the computer. This is not SAFE. I don't know how to manage this error

Regards

[Robbob]

Bozo,

Did you try using different polling rates as mentioned by other users?

And the ones that experienced this before, did you ever come across a solution?