I have started with an Atmel Start project:
My goal is to have a usb hub connected to this demo board: SAM V71 Xplained Ultra Evaluation Kit
The problem is atmel doesn't supply a hub driver, and they haven't responded to our questions about this. So I have been attempting to write one based upon the msc and other drivers they do provide.
Currently I'm having an issue when I connect the USB hub. It is returning a STALL when I send a GET_DESCRIPTOR request with the type DEVICE. This seems odd to me because other USB devices such as a flash drive or USB to serial converter do not reply STALL to the same request. In fact the Flash drive goes through the entire enumeration process and msc installation so that I can successfully read and write to the drive.
I am detecting the stall via a single break point set in the STALL handling section of the pipe handler.
I have been reading the Universal Serial Bus Specification Rev 2.0 but I can't find any differences between the way to read descriptors from hubs vs other devices. And I don't understand why a STALL would ever be sent in reply to a GET_DESCRIPTOR request.
Thanks
Just in case this is useful for anyone else. The issue I was having was apparently caused by the compiler optimization settings. Specifically I had change this setting to: "None (-O0)", after changing this back to the default I have had no problems enumerating USB devices. Picture of Optimization configuration
My colleague discovered this because of a seemingly unrelated problem which was causing Hard faults and Bus faults on the chip, these were also fixed by switching back to -O1. It seems -O0 needs to be used with a grain a salt or not at all on this chip.