USB to Serial

ID #1093

In Windows 7 the Com Port numbers for multi-port VScom USB-COM adapters are not sequential. Why, and how to avoid that?


Thanks to the driver installation in Windows 7, this is a known effect.

From Windows 95 up to Vista drivers for new hardware have been installed in a predictable sequence. In the case of serial or parallel ports this results in convenient and easy-to-understand port number assignment. This also applies to numbered components like Ethernet adapters.

Since Windows 7 Microsoft not only hides the "Add New Hardware" Wizard. Further it attempts to check for available driver software on Windows Update, before installing drivers already available on the system. On top of that the drivers for all components try to install at the same time, i.e. the installations run in parallel. Now the first successful process gets the first number, and so on.
Obviously this adds some random to the outcome.

How to avoid that problem:
That is difficult as far as we know. Customers may install the driver prior to connecting the USB-COM hardware. This way the installation has a better chance of coming out with sequenctial numbers. But there is no guarantee, sometimes the result requests a repair.

How to repair that problem:
At first there is the option of simply renaming the USB Com Port in the Windows Device Manager. Simple for a few ports, but time consuming for many Com ports.

Another option is to delete all the USB-Serial ports in the Device Manager. Attention: De-select the option to remove the drivers from the system. They must remain installed.
When that is done, in the same way delete all the USB Serial Adapters in the USB section of the Device Manager.

Finally let the Device Manager search for New Hardware. It will re-detect the USB-COM hardware, and the serial ports. Since the drivers are still installed on the system (and partially loaded), the process finishes much faster. Especially all ports need the same short time, typically resulting in a convenient number sequence.



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Last update: 2012-11-14 09:45
Author: Support
Revision: 1.1

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