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From: Andy Moreton <andy DOT moreton AT artimi DOT com>
Subject:  Re: Problem opening new serial ports
Date: Wed, 6 Aug 2008 09:09:16 +0000 (UTC)
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On Wed, 06 Aug 2008 02:37:41 GMT, Gary Johnson wrote:

> On 2008-08-05, Gary Johnson wrote:
[snipped] 
> OK, I did some Googling and found a "Cygwin USB-to-Serial HOWTO" 
> (http://tmp.ua964.com/cygwin-usb-to-serial-howto/) and a thread in 
> this list from May, both mentioning Cygwin's limit of 16 com ports.  
> They also say that this is in the FAQ, but I sure couldn't find it 
> there.  So it looks like my choices are:
> 
> 1.  Wait for 1.7 (I'm currently using 1.5.25(0.156/4/2).
> 2.  Build my own cygwin1.dll and change the limit to 64.
> 3.  Rename COM24 and COM25 to 16 or below.
> 
> I tried #3, but the drop-down list of COM ports says ports COM1 - 
> COM23 are "(in use)", yet only COM1, COM2, COM4, COM5, COM24 and  
> COM25 are in the Device Manager List.  The other ports were probably 
> taken by various USB devices I've plugged in at one time or another 
> but am no longer using.

Open Device Manager, and click on "Show Hidden Devices" on the "View" menu.
Click on the "Ports (COM & LPT)" subtree, and look for greyed out ports. On 
each of the greyed out ports, right click and choose "Uninstall". Do the 
same thing for any geyed out device in the "USB serial bus controllers" 
subtree if you find any entries for USB serial ports there.

Once you have done that, you should then be able to reuse the previously 
occupied COM port numbers.

    	AndyM


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