NCM On windows 10

[fabien251]

Hi everyone,

I just wrote a new program using TinyUSB with an STM32L476RGT6. I'm trying to implement a web page with LwIP that is accessible via USB using NCM from TinyUSB with the net_lwip_webserver. It works very well on Windows 11, but my device is not recognized on Windows 10 (error 28) ! Does anyone know why?

Fabien

[HiFiPhile]

On windows 10 you need to install the driver manually, choose Microsoft -> UsbNcm Host Device

[HiFiPhile]

I believe the issue is in Microsoft's side, Windows 10's NCM driver is not configured to do device binding automatically.

[fabien251]

Thanks for your reply, @HiFiPhile.
That might be the case, but I still don't understand why some devices are detected on Windows 10 and others are not. Do you know what could be causing this issue? I know that the working one uses an RP2040 and TinyUSB—could the microcontroller be related to this problem?

[HiFiPhile]

I don't think MCU make a difference. Are you sure it was recognized on first plug in ? Maybe make a descriptor dump to see the difference.

[fabien251]

Yes, it was recognized on the first plug-in. As I observed on Wireshark, Windows 10 doesn't send the GET_STATUS_REQUEST, unlike my Windows 11. I'm a beginner with USB, so any guidance would be appreciated.

[offlinemark]

Hey @fabien251 - On Win10, NCM devices are required to send a Microsoft OS descriptor for the NCM driver to autoload. Not sure exactly what happens at the USB level, but on Linux, this is done via the below in configfs.

echo 1       > os_desc/use
echo 0xbc    > os_desc/b_vendor_code
echo MSFT100 > os_desc/qw_sign

echo WINNCM   > functions/ncm.usb0/os_desc/interface.ncm/compatible_id

See vpelletier/python-functionfs#20.

Windows also caches info about devices and may not request OS descriptors if a device previously didn't have any. You can clear this registry key to reset this cache.

HLKM\SYSTEM\CurrentControlSet\Control\UsbFlags\vvvvpppprrrrr

https://learn.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors

HTH!