Unknown USB Device (Device Descriptor Request Failed)

Question

Plugged a USB device into my machine & I get this massage "Device not recognized". When I go to the device manager & select the unknown device it gives me this: "Unknown USB Device (Device Descriptor Request Failed)". The USB works on my Laptop at home.

Answer 1

Hi,

In this case, try other USB ports on your desktop, if possible with a different cable. Usually, the "unknown USB" error indicates a problem with the USB port or cable, suggesting a physical fault.

We can try resetting the USB controller if the problem persists after testing with a different cable and USB ports.

Thanks

Answer 2

"Unknown USB Device (Device Descriptor Request Failed)" means Windows tried to enumerate the USB device but could not read a valid device descriptor from it. In this state, Device Manager typically shows:

• Device ID: USB\\VID_0000&PID_0000
• Hardware/Compatible ID: USB\\UNKNOWN

According to the USB driver stack behavior, this happens when one of these fails during enumeration:

1. Port reset request times out.
2. The Set Address request for the device fails.
3. The request for the device’s Device Descriptor fails.
4. The USB Device Descriptor is malformed and fails validation.
5. The request for the Configuration Descriptor fails.
6. The USB Configuration Descriptor is malformed and fails validation.

In the detailed case study, tracing showed that the device stalled the standard control request GET_DESCRIPTOR(DEVICE) on endpoint 0 instead of returning its device descriptor. When that happens, enumeration cannot continue and Windows marks it as an unknown USB device with this error.

Because the same USB device works on another machine, likely causes on the affected PC include:

• Electrical/port issues (specific USB port or hub not behaving correctly).
• Timing or signal quality problems on that host controller that cause descriptor reads to fail.
• A hub or cable in between that interferes with enumeration.

Practical steps based on the documented behavior:

1. Try different physical connections
   • Plug the device directly into a different USB port on the PC (avoid front-panel ports or unpowered hubs if possible).
   • If using a USB hub or extension cable, remove it and connect the device directly.
2. Power-cycle and rescan
   • Shut down the PC completely (not just restart), disconnect power for a few seconds, then power it back on.
   • After boot, open Device Manager, select the computer name, then use Action → Scan for hardware changes to force re-enumeration.
3. Check for repeated enumeration failures
   • If the device continues to appear as USB\\UNKNOWN with Code 43 and the same message, that confirms Windows is repeatedly failing to get a valid device descriptor from that device on this host.

If the device consistently enumerates correctly on other computers but always fails with "Device Descriptor Request Failed" on this one, the issue is most likely with the specific USB controller/ports or cabling on the problematic PC rather than with the device driver or Windows configuration.

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References:

• Case Study: Troubleshooting an unknown USB device by using ETW and Netmon