Instrument Control (GPIB, Serial, VISA, IVI)

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Instruments with same VISA name

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I have a setup with many instruments being controlled from a central computer. The program that I'm writing interfaces with a coherent OBIS laser through the VISA port ASRL8::INSTR, which works just fine. However, I need to add an Arduino to the setup, and the Arduino also has the name ASRL8::INSTR. I don't need to use VISA to control the Arduino, but having it present in the system interferes with my ability to control the laser. 
I thought that VISA names were supposed to be unique. How can I resolve this conflict? 

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Accepted by topic author BrendanMitchell

This implies you have two devices using the same COM port.  That sounds like a Windows level issue.


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You were correct, changing the COM port from the device manager solved the issue. 
Pardon my ignorance, but this article seems to say that a "COM" name is an alias that serves only as a more user-friendly way of referring to a resource's "real" name (such as ASRL8::INSTR, in this case). This implied that the ASRL name is a more fundamental thing than the COM name. 
However, if I understand correctly, it seems that underlying the VISA resource name is the actual COM port, which is in fact more fundamental than the resource name. 

Am I correct in concluding that the resource's COM port and its VISA alias are two distinct (and virtually unrelated) things, even though both of them are called "COM8"?

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@BrendanMitchell wrote:

Am I correct in concluding that the resource's COM port and its VISA alias are two distinct (and virtually unrelated) things, even though both of them are called "COM8"?


"ASRL8::INSTR" directly describes the resource being used.  If using VISA Find Resource, "Canonical Name" is the term used.  Alias is a simpler name to point to a resource.  The default alias for a COM port 8 is "COM8".  In MAX, you can actually change the alias to something like "laser", and the alias will still point to COM8.


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