Instrument Control (GPIB, Serial, VISA, IVI)

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Testing connection to MD-CC4 USB RS422 for a mdrive stepper motor made by Schneider

I am new to LabView and I am trying to fix a script that hasn't worked in over a year at my university. I have a stepper motor that I would like to control via LabView. The LabView version I have is LabView 2013. The stepper motor is an mdrive 23 motor driver plus made by Schneider. I was able to successfully establish a communication with the IMS Terminal that came equipped with the motor via a MD-CC4 USB to RS422 Comm Converter. However, I am having trouble establishing communication with LabView via the same USB.

I am using the following two links as references: link 1 and link2


I went to MAX and was able to see the communication link ASRL[board][::INSTR] (which is shown in the screenshots attached below which in this case it is COM6) however I don't see any option where for the Open VISA Test Panel. Thus, I am unable to test the communication and not sure how to proceed? I am using LabView 2013, any suggestions or help will be extremely appreciated. The script worked over a year ago but I was tasked to fix it and not sure what my next steps are.

I have attached my VI and screenshots of the MAX terminal that I have. Also, I am unable to find the NI-VISA app, is that app necessary?

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Message 1 of 21


I assume you did not write this vi.

All those cases and especially the sequence structure should not be necessary.

Please write down what the vi needs to do and add the missing part

Anyway use error wires to connect vi's that should operate in sequence. That is called sequencing by wiring and the LabVIEW compiler makes sure that a vi or subvi only will be executed when all input wires have a value. Either from a constant, a calculation or a previous vi.

I can fix a few of these but not better with a bit more information.

greetings from the Netherlands
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Message 2 of 21


Correct I did not write the VI. The VI was written by a graduate student a few years ago but that student has since left and now I was tasked to fix it. In regards to the functionality needed I have attached a manual that summarizes what the VI needs to do as you requested. 

My first urgent task is to first see if there is communication between the LabView and the driver via the RS422 USB. I used the reference link I posted earlier above but the features in that link was missing so I am not sure how to go about testing the communication. Is the first step is to establish a communication between LabView and the motor, correct? If so, how can I do that? Or is there a different approach I have to do? It works fine with the built in IMS terminal but I am unable to make it work with LabView.

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Message 3 of 21


Thanks for the manual, stil asking for the missing subvi but I now understand what is needed.

greetings from the Netherlands
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Message 4 of 21

I am sorry I don't have the subvi on me and the University is open on Monday two days from now. I can get the subvi on that day.

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Message 5 of 21

No problem. Probably a nice calculation

greetings from the Netherlands
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Message 6 of 21

Hmm what do you mean by nice calculation? 

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Message 7 of 21


I meant that the missing vi probably a calculation is.

greetings from the Netherlands
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Message 8 of 21

Oh I see, but in regards to testing the communication via the RS422 USB, how do I go about doing that?

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Message 9 of 21


I rewrote Init motor to a subvi that is a bit clearer to read and has error messaging.

Try to run this vi and when an error occurs it will tell you the error.


This one also is a bit easier to adapt when needed,


I attached the vi and the changing implementation as pictures.

First the original

2021-02-08 15_54_45-Document1 - Word.jpg

2021-02-08 15_55_59-Initialize Block Diagram.jpg

greetings from the Netherlands
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Message 10 of 21