STM32N6 two USB device classes running simultaneously

[PeterPan]

Hello,

I have custom STM32N657 board with two USB ports. There is USBX device video class running on USB Port 1 and streaming video - all good here, working well.
I would like to get exactly the same functionality on USB port 2 - second USB video device. The STMCubeMX supports only one USB port in device mode - that is also limitation of USBX
"Only one USB device controller can be defined at any time to operate in device mode."
azure-rtos_rtos-docs/rtos-docs/usbx/usbx-device-stack-2.md at main · azemb-todd/azure-rtos_rtos-docs · GitHub

What is the best approach to get second USB port running in USB video class in device mode?

[FBL]

Hi @PeterPan 

For multi interfaces device, we recommend to build a composite device. Otherwise, you can only have one USB controller in device mode at a time. USBX’s device stack is designed around a single device controller instance.

I hope this helps!

[PeterPan]

Hi @FBL 

Thank you for quick reply. There are two image sensors connected to the board so I need two video streams. Also, essential is double the bandwidth. What are other possible solutions?

[FBL]

Hi @PeterPan 

If both video streams can be compressed or down scaled enough to fit within a single USB HS link, the recommended approach is to build a composite UVC device on one STM32N6 USB port.

In practice, this means you keep one USB device controller active in device mode.

You define one configuration descriptor that contains: Two UVC interface sets (one for each camera: VideoControl + VideoStreaming).

The host will typically see two separate webcams coming from a single USB device.