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Problems With USB to Serial Adapter

Hi I am troubled by a problem I am having and cannot find the reason why. I am running a program that runs 3 paraell loops. 1 loop reads 4 bytes from the serial port  at a rate of 38400 bps and places that data in a Queue. The second loop reads from the cue and separates data into 3 2D arrays and saves those arrays to temp files once the array sizes reach 500 elements. The third loop reads those temp files and does all the analysis. The problem i am having is when I use a USB to serial adapter Labview seems to randomly stop reading from the port and freezes until I eject the adapter. I however do not get this problem when I use a computer with a built in serial port. i need to be able to use the adapter to do tests in a machine lab. Does anyone have any ideas of how to fix this or why I'm having this problem. Thanks,



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Message 1 of 21

USB to serial adapters are notorious for causing these kinds of problems, especially if you're using Windows Vista or 7. You could try getting a newer version of the driver, if it exists, but really, the only sure way of avoiding this is buying an adapter which works properly.

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Message 2 of 21

Do you know of which adapters do work properly? I am using Windows 7 x64 but I tried the same program on a laptop running XP x32 and had the same issues. So if you know of an adapter that doesn't cause as many problems I would be grateful.

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Message 3 of 21

I have successfully used model USB2-4COM-M purchased from USB Gear on both XPpro and W7. ( ). Once it is configured through the hardware manager, labview treats it like any other port. I have not run it faster than 9600, though, so I'm probably an easy job.


I have no affiliation with this product or supplier.


Message 4 of 21

Have you heard of anyone using a cheaper one? I only need 1 port and that is a little to expensive I think. Should I look for ones that are certified to work with my version of windows because I do know the ones I am using are a few years old so that could be why.

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Message 5 of 21

I bought 3 different models of the single port ones from the same company in the past year. I bought different ones because I worried that I might have exactly the sort of problems you're having. The first 2 I opened worked perfectly and I never got to the 3rd. All of them were under $20. That's probably what I would try if I were you. The tricky thing with buying these is that there are dozens or hundreds of generic manufacturers repackaging probably 2 or 3 chipsets, so you might buy 2 that look different and have them be the same inside. That said, my experience is that some of the cheap ones work just fine.

Message 6 of 21

I've used quite a few of the IOGear brand and have never had a problem.

Message 7 of 21

I have used Belkin with little or no problems on Windows XP.


The first time I used the USB adapter, it would always lock up when I tried to configure the serial port it was connected to.   I had to uninstall the drivers and then reinstall again from a differerent source.  After that I have never had any problems. 


F5U409 is the model we use.





Message 8 of 21

What OS were you using with the ones from IO Gear?

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Message 9 of 21

I've used the IO Gear mainly on XP, but have also used them at home on my Vista PC.  I don't have any Win7 PC's for comparison.

Message 10 of 21