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The difference in the action of IgnoreHWSerNum of USB2.0 and USB3.0

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I googled around a lot but was unable to find an answer to this problem, So I am putting it here.

I simply want that for a USB port, the assigned COM port number does not change for devices with a different serial numbers.

On investigating I found out that by configuring IgnoreHWSerNum Key in the Registry, registration of Serial Numbers for a device can be ignored.

Hence I set the IgnoreHWSerNum in the following Registry Key:

  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\usbflags

To Test I inserted one of the device in the USB 2.0 port.

The device was detected as COM3

Then I tried an another simillar device with different serial number in the same port.

I could confirm that this one was also detected as COM3

On checking the entries corresponding to "Vendor ID" and "Product ID" in the following Registry Key

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\USB

.. I cannot find the serial numbers of the devices, which is obvious.

But when I try these two devices in a USB 3.0 port I get different COM port number for each.

1st device: COM5

2nd device: COM7

On checking the entries corresponding to "Vendor ID" and "Product ID" in the following Registry Key

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\USB

... I find the devices serial number, which means that the IgnoreHWSerNum entry did not work.

Does it mean that IgnoreHWSerNum registry settings does not work for USB 3.0? Or is there another place for the settings?

If not then how can I assign fixed COM port numbers to the devices with different serial numbers for USB 3.0?

Any help is appreciated!


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