I’m using AzureRTOS USBX to write a Mass Storage application for a custom ARM SoC that isn’t yet on the market. The behavior I observe when I flash and run my program is that it gets through initialization without returning errors, and the device ACKs the request for a Device Descriptor, but it never responds to that request.

I have a working USBX CDC ACM application, so I do know the USB peripheral hardware on the SoC is functional. I’m using the same hardware initialization steps for the Mass Storage application as the CDC ACM application.

main calls tx_kernel_enter(). tx_application_define does the following:

1. Create a byte pool
2. Allocate device stack memory from that byte pool
3. Initialize USBX (ux_system_initialize)
4. Initialize device stack with descriptors (ux_device_stack_initialize)
5. Register a Mass Storage device (ux_device_stack_class_register with MSC information)
6. USB peripheral hardware initialization
7. Allocate the app thread memory from the byte pool
8. Create a thread with an empty infinite loop

I tried mimicking a Mass Storage application for STM hardware and replaced their hardware initialization with our own. Hopefully someone can point out a step that I’m forgetting or something that would lead to the device ACK but not responding to the request for the Device Descriptor.

I can post some of my code if this is not enough information, but the hardware initialization itself I’ll have to keep hidden.