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The General USB Process
How Does the Host Know a Device’s Requirements?
Interface
Descriptor
//------------------------------------------------------------
// Sample Standard Interface Descriptor Type
// Definition Fields
//------------------------------------------------------------
Length (9 bytes)
Descriptor Type (INTERFACE)
Interface Number
(interface number, zero based, and
incremented once for each new interface descriptor
.
)
Alternate Setting (value used to select alternative
setting)
Number of Endpoints (number of Endpoints used for
this interface)
Interface Class
(e.g., HID, mass storage))
Interface Sub Class (subclass Code - assigned by
USB Org)
Interface Protocol
(Protocol Code assigned by USB
Org)
Index (Index of String Descriptor Describing this
interface)
The interface descriptor groups
endpoints into functional groups
that perform a single feature of
the device.