Windows 7 com port numbering.

Does anyone know how to make Windows 7 stick to The same com port number.
It's a pain for it to allocate a random port number each time I connect my usb serial cable in.
I have to change the settings in the plc communications which is a convoluted affair just to get online.
Thanks

As an addendum to this, I can't change the number in win 7 to what my plc is set to as it says they are all in use....which they are not

The underlying factors are a little complex, having to do with Vendor ID and Product ID and Serial Number identifiers and USB driver settings.

A small number of USB/Serial device vendors use a "locked serial number", where every device has the same serial number so they can be plugged in anywhere on the PC and give the same COM port number. But only one of them can be connected to the same PC.

Some drivers can be configured to ignore the Serial Number, and use only the location of the USB port. So any device plugged into the same USB port gets the same COM port number.

But in general, if you use a lot of USB/RS232 devices and plug them in to different ports, you occasionally have to do some PC maintenance and delete some or all of the COM port devices in the Windows Device Manager.

I like the Tripplite/Keyspan USA-19HS because its handy device utility lets you easily change the COM port number, instead of having to use the Windows Device Manager.

I have one USB serial I carry for each laptop.

Even using the same adapter and plugging it into a different USB ports will cause Windows to give it a different COM port number.


The only way around this is to plug it into each USB port on the computer and after it installs go to Device Manager and change the COM number. It will pop up that that number is being used by another device, just click OK and now whichever port you plug into will be the same COM port number.

I sometimes have to do this with flash drives that certain programs are expecting to be a specific drive letter. For that I have to go to Disk Management and change the letter with it in each USB port. Sometimes Windows does not want to do this.

Under device manager, open comm ports and right click on the comm port you would like to change and select properties. Click port settings tab and then the advanced button. From here you should be able to set the port number. What ever adapter you are taking will have to be set this way also next time you use it, just remember what was used.
Oh and make sure the serial drivers in RSlinx or and other software is not running.

You need select show hidden devices, then you can uninstall old ones.



http://woshub.com/how-to-clean-up-and-reset-com-ports-in-windows-7/

I use device manager to force all my USB/serial devices to COM1. Windows barks at me, but I do it anyway. Once in a great while, Windows will get amnesia and I have to repeat the process. This has only happened once with my Windows 10 PC, and maybe twice in 5 years on Windows 7. You may have to do this for each USB port separately, but it should work and "stick" about as consistently as anything stays fixed with Windows.

Great info. I like to use same com port, then start and stop drivers manually in Linx depending on what I'm talking to.

Thank you all.

I have managed to delete all com ports (using the hidden devices technique)
And set the com port to the same number each time I plug in.

Ken Roach said:

I like the Tripplite/Keyspan USA-19HS because its handy device utility lets you easily change the COM port number, instead of having to use the Windows Device Manager.

Click to expand...

I use this too and really like it because the little utility program from the manufacture makes, the COM port # stays the same no matter which USB port I plug it into. That and it seems to work on everything I've thrown at it.

For Ethernet COM ports I always use Moxa.

Their utility also sets the COM port number regardless of Device Manager and it will be that port number anywhere on the network.

Plus, they can be used by more than one computer - but not at the same time! If not in use any computer with the Moxa utility set up can use it.