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  1. #1
    Plutonium Lounger Leif's Avatar
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    We use USB to RS232 converters at work - a lot of industrial electronics such as modems still use RS232/RS485 - and we are having an issue with allocated COM ports.

    Typically, you install the device, and the first available COM port is allocated to that specific device. You plug in another, and the next port number is used. The system remembers which port number has been allocated to which specific device, so if you connect it again, it is given the same (original) number. So far, so good - Device Manager shows the port installed and working:

    [attachment=82762:x.gif]

    However, for various reasons such as wear and tear, adapter sharing, etc., some workstations are beginning to use up port numbers at a great rate. A new adapter is plugged in, and the next number is allocated. The problem arises when you want to use software which can only see, for example, COM1 to COM8. Looking at the properties, is appears possible to change the COM port number being used, but as the next graphic shows, the system remembers all the other devices and ports it has used....

    [attachment=82763:y.gif]

    The ports shown as being 'In Use' above, are not (to all practical purposes) being used. It is possible to select a used one, but the following warning is shown:

    [attachment=82765:z.gif]

    Is there some way to safely claim back these port numbers? My only experience with recycling a used port number resulted in occasional BSD's, although that may have been coincidental. The only thing that occurs to me is to plug back in the device allocated to a specific port number and 'uninstall' it. But this is not practical when the device has been trashed.

    Any ideas anyone? This may not be XP specific, but a solution for XP would be welcomed!
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  2. #2
    Plutonium Lounger
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    Leif,

    I haven't tried this, so it is a complete guess.

    If you show hidden devices in device manager (see MSKB article 315539) then you can delete the ones you no longer use. Does this free up the COM ports?

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    [quote name='Leif' post='764585' date='10-Mar-2009 08:50'][/quote]

    Have you tried deleting the port and then re-booting to let Windows re-discover it?

    Joe

  4. #4
    Plutonium Lounger Leif's Avatar
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    [quote name='StuartR' post='764605' date='10-Mar-2009 14:57']Does this free up the COM ports?[/quote]

    As Sally said, "Yes, Yes, YES!"

    Now I can see them, I can delete them - thank you!

    ###

    Thanks Joe - the problem was that I could only see the used/allocated Com ports when I tried to select them in the Advanced window drop-down, and there seemed no (right-click) option to delete.

    ###

    (And in case you were wondering, COM12 and COM13 were allocated to the USB connection to my Sony Ericsson...!)

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    [quote name='Leif' post='764622' date='10-Mar-2009 10:42'][/quote]

    Glad that worked!!! You mean you couldn't read my mind about using Device Manager. I could've sworn that I typed that.

    Joe

  6. #6
    Silver Lounger
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    [quote name='Leif' post='764622' date='10-Mar-2009 16:42']As Sally said, "Yes, Yes, YES!"

    Now I can see them, I can delete them - thank you!
    <snip>[/quote]
    But Leif! Search, Search, SEARCH! All together now; search, search, search!

    Our ejhattc (Edward) had exactly this problem back in 2003; see this thread, and yes, the best way to deal with it is to show "non present".

  7. #7
    Plutonium Lounger Leif's Avatar
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    [quote name='Argus' post='764649' date='10-Mar-2009 17:10']Our ejhattc (Edward) had exactly this problem back in 2003; see this thread, and yes, the best way to deal with it is to show "non present".[/quote]
    Ah, yes - thank you! Well, now you come to mention it... I just didn't think to look back that far.... [attachment=82772:laugh.gif]
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