Hi everyone,
I’m working on an STM32U5G9 using USBX + ThreadX.
I was able to make the device work as:
That part is fine. What I need now is more dynamic behavior: start the device as MSC, and when a button is pressed, stop USB, change the class to CDC-ACM and restart it (long term I’d like to switch arbitrary combinations of classes, but for now switching from MSC to CDC-ACM is the goal.)
From what I understand, I must stop USB so the host will re-enumerate using the new device descriptor, and I’m OK with that. However, every approach I tried ends in a HardFault when I restart with the other class. I suspect I’m missing a call or doing things in the wrong order.
How I start the device (this works):
/* Start device with MSC only (initial boot) */
/* First I insert CLASS_TYPE_MSC is "UserClassInstance" variable in ex_device_descriptors.c (not shown here), then: */
ux_device_stack_initialize(...);
/* Register MSC-only */
ux_device_stack_class_register(...);
HAL_PCD_Init(...);
/* Then I set the RX an TX Fifo for both MSC and CDC classes, even if only the MSC Is active */
HAL_PCDEx_SetRxFiFo(...);
HAL_PCDEx_SetTxFiFo(...);
ux_dcd_stm32_initialize(...);
HAL_PCD_Start(...);
How I try to switch to CDC-ACM (this leads to HardFault):
/* Stop device and remove old class */
HAL_PCD_Stop(...);
_ux_dcd_stm32_uninitialize(...);
HAL_PCD_DeInit(...);
ux_device_stack_class_unregister(...);
ux_device_stack_uninitialize(...);
ux_system_uninitialize(...);
/* change UserClassInstance to CLASS_TYPE_CDC_ACM in the ex_device_descriptors.c (not shown here) */
/* Restart with CDC-ACM */
ux_system_initialize(...);
ux_device_stack_initialize(...);
ux_device_stack_class_register(...); // CDC-ACM
HAL_PCD_Init(...);
HAL_PCDEx_SetRxFiFo(...);
HAL_PCDEx_SetTxFiFo(...);
ux_dcd_stm32_initialize(...);
HAL_PCD_Start(...);
At this point the device always ends up in the HardFault handler, but I suspect I’m missing a call or doing things in the wrong order.
Can anyone give advice, point out what is wrong in the sequence above, or share an example showing how to correctly stop and restart USBX with a different device class?
Thank you very much for your help.
