Author Topic: "Unknown Device" on all ports except first?  (Read 5551 times)


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"Unknown Device" on all ports except first?
« on: September 08, 2021, 11:07:03 am »
My colleague is testing a custom HID device of mine, which is using code from the NXP SDK (of which I'm not really a fan).
His machine is Windows 7.

The port that he plugged the device into the first time works fine.

If he moves the device to any other port it comes up as "Unknown Device".

The device works fine on my Windows 10 machine no mater what port I plug it into.
As I move the device to each port I get "Installing ...." as I expect.

Ideas, suggestions?


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Re: "Unknown Device" on all ports except first?
« Reply #1 on: September 09, 2021, 08:59:13 am »
First of all, give it a serial number, even if it's just "1".
When you plug something with a serial number into different ports in Windows it will realize that it's the same device and not have to "install" it.

An HID device should just work. Maybe there is something wrong with your descriptors?

Jan Axelson

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Re: "Unknown Device" on all ports except first?
« Reply #2 on: October 01, 2021, 09:37:04 pm »
Agree that a serial number might fix it though it shouldn't be necessary.

A device without a USB serial number string descriptor gets a new hardware key every time the device attaches to a port the device hasn’t been attached to previously.

Devices with USB serial numbers have one hardware key per physical device without regard to what port the device attaches to.