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The General USB Process
How Does the Host Know a Device’s Requirements?
Configuration
Descriptor
//------------------------------------------------------------
// Sample Standard Configuration Descriptor Type
// Definition Fields
//------------------------------------------------------------
Length (9 bytes)
Descriptor Type (CONFIGURATION)
Total Length (total length in bytes of data returned)
Number of Interfaces (number of interfaces present
for this configuration)
Configuration Value (value used by the
SetConfiguration request to select this configuration)
Configuration (Index of String Descriptor describing
this configuration)
Attributes (bus powered, self powered, remote
wakeup)
Max Power (Maximum Power Consumption in 2mA
units)
The configuration descriptor is a
header to the interface descriptors. It
specifies how this configuration of the
device is powered, what the
maximum power consumption is, and
how many interfaces there are. There
can be more than one configuration
descriptor (for example: if the device
can switch between self-power and
host-power).