topic Re: Programatically determine and select VISA COM Port Binding in LabVIEW

Programatically determine and select VISA COM Port Binding

nikvl — Wed, 17 Aug 2022 14:04:57 GMT

Hi all,

I'm working on an application whereby a user runs an automated test on a device, by comparing values from a reference (sensor) and the DUT. Both the reference and DUT communicate serially via USB Serial Port.

When the user clicks on "Connect", I want the program to automatically select the VISA COM ports and open communication in the background. For the reference sensor, since it's unchanging, it is relatively easy to set it (either through hardcoding or throug an ini file). However for the DUT, the port binding is ever increasing. What I mean is when I plug one DUT in, it shows for example, ASRL10 (COM10- USB Serial Port) , and when I disconnect the cable to plug it into the next DUT, it shows COM11 and so on and so forth. I want to avoid the user having a drop down box to select the specific COM port each time a new test with a new DUT commences.

I can easily list all the currently connected instruments and filter the USB Serial Ports out, however, how do I circumvent the port binding? I don't know the finite number of DUTs that will be tested and NI-VISA allows COM numbers until only 256. Is there a way to set the port binding (so I can create an alias like "DUT" or something in MAX)?

Thank you for any hints and help!

Re: Programatically determine and select VISA COM Port Binding

wiebe@CARYA — Wed, 17 Aug 2022 14:21:38 GMT

Make a short list (e.g. with VISA Find Resource function) and loop over them. Open each one (limit the access mode), and read properties to narrow down to the device (General Settings properties, like manufacturer, USB Settings, like serial number).

Re: Programatically determine and select VISA COM Port Binding

crossrulz — Wed, 17 Aug 2022 14:30:53 GMT

What I have done is get the list of serial ports with the VISA Find Resources. Then connect the DUT. Do the find again and filter out the ports that were previously found. What is left should be the resource for the DUT.

Re: Programatically determine and select VISA COM Port Binding

nikvl — Wed, 17 Aug 2022 14:43:11 GMT

Hello and thank you for your response.

Getting the list is not the problem nor the resource for the DUT (using the PC's Device Manager was sufficient). Right now I only have two sample DUTs and what I have noticed that they have different port bindings. And while right now it's easy to say COMXX belongs to DUT 1 and COMYY belongs to DUT 2, my question is what happens when the COM number exceeds 256 (or whatever finite number it can hold)? The communication port from the DUT to USB is through a USB-Mini B cable (I'm assuming a RS232 FTDI connection beyond that but the person I could ask to be sure is unavailable). The test application is meant to last for years and every new DUT will just get a new COM number (or am I mistaken?)...

Re: Programatically determine and select VISA COM Port Binding

paul_cardinale — Wed, 17 Aug 2022 16:07:16 GMT

Maybe this will work for you

Re: Programatically determine and select VISA COM Port Binding

billko — Wed, 17 Aug 2022 16:16:54 GMT

I am assuming the USB/COM port adapter is embedded in the UUT and that is why it gets a new COM port each time?

Re: Programatically determine and select VISA COM Port Binding

RTSLVU — Wed, 17 Aug 2022 17:14:51 GMT

@nikvl wrote:
while right now it's easy to say COMXX belongs to DUT 1 and COMYY belongs to DUT 2, my question is what happens when the COM number exceeds 256 (or whatever finite number it can hold)?

This is a Windows issue and all you can do is go into the Windows Device Manager and manually remove the ports marked as "in use" by Windows.

Re: Programatically determine and select VISA COM Port Binding

nikvl — Thu, 18 Aug 2022 04:40:18 GMT

Yes, I think so. Since all I get is the assembled unit and to communicate all I needed was the USB cable. I wonder what would happen once all the COMS are assigned? Would there an error?

Re: Programatically determine and select VISA COM Port Binding

nikvl — Thu, 18 Aug 2022 05:45:03 GMT

^ the above response was to @billko

Re: Programatically determine and select VISA COM Port Binding

wiebe@CARYA — Thu, 18 Aug 2022 08:13:02 GMT

@nikvl wrote:

^ the above response was to @billko

Next time use the quote button 👍:

Re: Programatically determine and select VISA COM Port Binding

VinnyAstro — Thu, 18 Aug 2022 12:57:51 GMT

@nikvl wrote:

I wonder what would happen once all the COMS are assigned? Would there an error?

Tbh, I never really understood how exactly the COMs ports are assigned. But through my work I'm using a lot of USB to XXX adapters (most of the time using FTDi chips) and we have some -very- old computers running some tests. And very often we plug in a new adapter. We never came across an issue of all COM ports being used. And I think that's because they are automatically re-assigned. You will face an error if you plug more than 256 devices at the same time (if I understood well this article).

What also happened to me in the past is that I used the alias re-naming function in NI-max once because a computer was connected to too many stuff and it became annoying to remember and find the right one by chance, but one day, while connecting something completely different, the same alias popped-out in my VISA ressource name control, which led me to the assumption above.

Re: Programatically determine and select VISA COM Port Binding

nikvl — Thu, 18 Aug 2022 13:29:59 GMT

@VinnyAstro wrote:

Tbh, I never really understood how exactly the COMs ports are assigned. But through my work I'm using a lot of USB to XXX adapters (most of the time using FTDi chips) and we have some -very- old computers running some tests. And very often we plug in a new adapter. We never came across an issue of all COM ports being used. And I think that's because they are automatically re-assigned. You will face an error if you plug more than 256 devices at the same time (if I understood well this article).

What also happened to me in the past is that I used the alias re-naming function in NI-max once because a computer was connected to too many stuff and it became annoying to remember and find the right one by chance, but one day, while connecting something completely different, the same alias popped-out in my VISA ressource name control, which led me to the assumption above.

Yeah I use lots of USB fr communication but most of the time the USB-serial interface is a single, separate, constant part that I work with so I never really thought about how this might influence the COM ports other than occassionally manually reassigning them in the device manager. However, I have a hunch about how I might get around this but I'm currently away from my instruments. Will report back if it pans out.

Re: Programatically determine and select VISA COM Port Binding

VinnyAstro — Thu, 18 Aug 2022 13:30:35 GMT

Otherwise, given your initial problem, in my company we have somehow a similar issue: We have a lot of already connected devices, and it's a pain to go through all of them and find the right one. So I developed this VI that automatically detects when a device is connected to a COM port and automatically sends this out (or in my case connects to it)

I've made it more "general case" than what I use it for.

It does require that your device is not connected when you run the VI though.

Hope this helps.

VInny.

Re: Programatically determine and select VISA COM Port Binding

VinnyAstro — Thu, 18 Aug 2022 13:34:19 GMT

@nikvl wrote:

Yeah I use lots of USB fr communication but most of the time the USB-serial interface is a single, separate, constant part that I work with so I never really thought about how this might influence the COM ports other than occassionally manually reassigning them in the device manager. However, I have a hunch about how I might get around this but I'm currently away from my instruments. Will report back if it pans out.

I personally never had to manually reassigned anything. I've never faced any duplicates in the COM port or errors due to something similar to this. So I assumed that windows is friendly enough to do that by himself (which could lead to the issue I had where a device's alias that I named "Motor" was used for a completely different device...)

Re: Programatically determine and select VISA COM Port Binding

nikvl — Thu, 18 Aug 2022 13:37:30 GMT

@VinnyAstro wrote:

Otherwise, given your initial problem, in my company we have somehow a similar issue: We have a lot of already connected devices, and it's a pain to go through all of them and find the right one. So I developed this VI that automatically detects when a device is connected to a COM port and automatically sends this out (or in my case connects to it)

I've made it more "general case" than what I use it for.

It does require that your device is not connected when you run the VI though.

Hope this helps.

VInny.

Thank you. This looks interesting, will have to try it out when I get back. Say, did you do something to the .vim search 1D-Array? Yours outputs a boolean and the standard LabVIEW one the index of element...

Re: Programatically determine and select VISA COM Port Binding

VinnyAstro — Thu, 18 Aug 2022 13:55:16 GMT

nope, I'm using the Search Sorted 1D Array.vim located here which is different from the Unsorted one. And because Find VISA already sorts the array...

I still need to update my QD shortcut for it, s1d was practical, but still send to the "normal" search 1d array vi which apparently is not supported anymore

Re: Programatically determine and select VISA COM Port Binding

crossrulz — Thu, 18 Aug 2022 13:57:25 GMT

@VinnyAstro wrote:

I still need to update my QD shortcut for it, s1d was practical, but still send to the "normal" search 1d array vi which apparently is not supported anymore

The primitive is still supported, it just isn't in the palettes anymore. But if you dig deep enough in the VIM, you will find the primitive.

Re: Programatically determine and select VISA COM Port Binding

VinnyAstro — Thu, 18 Aug 2022 14:24:27 GMT

@crossrulz wrote:

The primitive is still supported, it just isn't in the palettes anymore. But if you dig deep enough in the VIM, you will find the primitive.

Yes that's true, I found it once, but I just find annoying to not have the easy shortcut working and have to adjust it 🙂

Re: Programatically determine and select VISA COM Port Binding

crossrulz — Thu, 18 Aug 2022 14:53:52 GMT

@VinnyAstro wrote:

@crossrulz wrote:

The primitive is still supported, it just isn't in the palettes anymore. But if you dig deep enough in the VIM, you will find the primitive.

Yes that's true, I found it once, but I just find annoying to not have the easy shortcut working and have to adjust it 🙂

Give this thread a good look through: https://forums.ni.com/t5/LabVIEW/Search-1D-Array-Changed-in-2020-SP1/m-p/4114744. Somewhere in there are a couple of setup VIs for adding the primitive back into the palette. I don't remember if the primitive was added back in 2021 or if I "fixed" it a long time ago.

Re: Programatically determine and select VISA COM Port Binding

t.n14 — Fri, 19 Aug 2022 08:28:18 GMT

We have a testing PC with the same problem, we use ComPortMan, completly worth it.

You can define fixed ports for specific devices and ports for constantly switching devices to be a specific port.

Timo