1,In the endpoint descriptor,when in isochronous transfer the bmAttributes's bit 3:2 defines Synchronization Type as :No Synchronization/Asynchronous/Adaptive/Synchronous, what's the differences among them? To maximrize the transfer speed, how to set it?
2,The bmAttributes's bit 5:4 defines Usage Type as :Data endpoint/Feedback endpoint/Implicit feedback Data endpoint, what's the differences among them?
Looking at your question I assume you're talking about a specific USB class protocol and not generic USB protocol. Is my understanding right? If so please let me know the protocol you're referring to, if you can provide me a link to the document you're referring it would be much better.