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Forum Index : Microcontroller and PC projects : Creeping COM Port Numbers

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crackerjack

Senior Member

Joined: 11/07/2011
Location: Australia
Posts: 164

Posted: 02:03pm 07 Oct 2011

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Hi All,

This is possibly a Windows O/S issue, but wanted to know if anybody else has encountered it while using their Maximite:

I am running Windows 7 and from time to time, when I plug my Maximite into a USB port, I see Windows trying to install a new driver (I already have the driver installed). After this my Maximite appears on a new COM Port number. It started at #4, then after a few of these occurrences, it is now on #7. It's a bit of a pain because some of my comms between the PC and my Maximite is setup to expect a given COM port number, but it keeps changing.

I will look into a resolution, but thought I'd verify here first if anybody had encountered this "virtual serial COM port creep".

Thanks,

Lance.

Dinosaur

Guru

Joined: 12/08/2011
Location: Australia
Posts: 323

Posted: 09:38pm 07 Oct 2011

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Hi All

Yes have had that happen, but not sure if it was creep or another device taking that port. So now,I do this:
Control Panel /System / Device manager / Ports (Com & LPT
Select the Silicon Chip Serial Port / Properties /Port Settings /Advanced Settings
and select the port you want to use / OK.
You will get a warning about the port already being used, but if you know that that is false (Windows keeps them reserved from the last time you plugged a device in that port)then /Yes.
From then on it will always use that port.

Hope that helps

Regards

Regards
Hervey Bay Qld.

seco61
Senior Member

Joined: 15/06/2011
Location: Australia
Posts: 205

Posted: 09:43pm 07 Oct 2011

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Hi Lance.

Windows will (by default) use a different COM port number if you attach the USB cable/device to a different USB port. It is Windows attempt to differentiate between (possibly) different devices that have the same VID/PID.

I also do as "Dinosaur" suggested.

Regards

Gerard (vk3cg/vk3grs)

crackerjack

Senior Member

Joined: 11/07/2011
Location: Australia
Posts: 164

Posted: 04:32am 08 Oct 2011

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Thanks Dinosaur and seco61 - I followed the steps and now also understand why this was happening. You guys are champs and help make this forum the great "place" it is to get help and share ideas.

Cheers,

Lance.

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