STM32N657: Implementing Dual CDC ACM in USBX Standalone Mode with X-CUBE-FREERTOS

[MSGokul]

Hi everyone,

I am developing a project on the STM32N657X0H3Q where I need to implement a Dual CDC ACM composite device.I am following the "Standalone" implementation to avoid a full ThreadX dependency, as I plan to integrate this with a FreeRTOS project (using X-CUBE-FREERTOS).
While looking at the USBX configuration in CubeMX and the ST Wiki (Introduction to USBX), I noticed the option
USBD_COMPOSITE_USE_IAD ( As seen in the picture).

If I enable USBD_COMPOSITE_USE_IAD , can I simply increase the number of CDC ACM class instances in CubeMX to 2?

Does CubeMX automatically handle the IAD grouping for the second CDC instance, or do I need to manually adjust the interface descriptors in the generated ux_device_descriptors.c ?

Can you provide an approach to configure this using MX? Which are all the files that should be edited to configure this.

[FBL]

Hello @MSGokul

Enabling USBD_COMPOSITE_USE_IAD in CubeMX is not sufficient for dual CDC ACM support.

/* Activate the IAD option */
#define USBD_COMPOSITE_USE_IAD						1U

You must manually edit the descriptors (in ux_device_descriptors.c) and register both class drivers, enable USE_USBD_COMPOSITE  and add composite builder class middleware as detailed in this article.