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

Thanks so much! Will attempt this first thing tomorrow afternoon and will update you. 

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Message 11 of 21

I have attempted to run the VI and an error did output. The error was -1073807298 (Hex 0xBFFF003E). I looked online and it seems to be an error due to other processes using the I/O ports of my device. I closed all application that may use that port and reattempted it and I still get that error. I have attached an image. Also, I have attached the subvi that you asked for as well. 

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Message 12 of 21


What is probably missing is the initialization of the port.

I found the following (not so beautiful construct) in seq 0 of your program.

2021-02-11 11_01_05-Motor_and_Stage_Control Block Diagram _.jpg

 This can better be replaced by the attached vi.

Build in a new vi the two vi's together as in this picture. I don't send you an implementation to get you test it yourself.


The wrong parts in the original is the use of local variables where that is not needed at all.

Instead of filling in a wrong COM6 the VISA resource name should be connected to the initialize vi.

And instead of filling a string with comment, this should have been the default value of VISA resource name. Now everybody has to change the code to get this running. So filling in COM4 is not sufficient.


Use both new subvi's the former had no connector connected.....

2021-02-11 11_18_32-Untitled 2 Block Diagram _.jpg


greetings from the Netherlands
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Message 13 of 21


I did send version LV2020, should be LV2013

Here they are

greetings from the Netherlands
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Message 14 of 21

What is the difference between the Open and the Initialize Sorry I am still new to LabView and trying to understand all the components.

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Message 15 of 21

Open VISA sets the serial line in the correct "mood".

Initialize motor sets the motor in a known state.

greetings from the Netherlands
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Message 16 of 21

I still unfortunately still get the same error using the vi's you have uploaded. I closed all applications that was making calls to the port. I even disconnected the power supply and the USB and I still get that error.


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Message 17 of 21

VISA: (Hex 0xBFFF003E) Could not perform operation because of I/O error.


The error just signals an IO error. This also can mean that the port is not opened at the correct baudrate or even that com4 or com6 are not correct. First step is to check if that error occurs in the open or in the first write. Anyhow your RS422 device should be found also in the windows device manager and needs probably more settings than just a buffer size setting.


Anyhow I now realize that I don't know the motor specification only the spec of the serial usb driver.


So what motor system are you talking to?

greetings from the Netherlands
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Message 18 of 21


Sorry for late reply! The motor is a "MDRIVE 23 motor driver plus by Schneider". The motor comes with an already installed software which is an IMS terminal. I used that terminal to successfully communicate to the motor with the same rs422 usb but it isn't able to communicate with the labview. 

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Message 19 of 21

Also, I believe the error only occurred on the WRITE vi because I don't recall seeing any errors when I ran OPEN vi

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Message 20 of 21