The Configuration Descriptor (USB_CONFIGURATION_DESCRIPTOR) contains information about the device power requirements and the number of interfaces it can support. A device can have multiple configurations. The host can select the configuration that best matches the requirements of the application software.

Offset	Field	Type	Size	Value	Description
0	bLength	uint8_t	1	Number	Size of this descriptor in bytes.
1	bDescriptorType	uint8_t	1	Constant	Configuration Descriptor Type = 2.
2	wTotalLength	uint16_t	2	Number	Total length of data returned for this configuration. Includes the combined length of all descriptors (configuration, interface, endpoint, and class or vendor specific) returned for this configuration.
4	bNumInterfaces	uint8_t	1	Number	Number of interfaces supported by this configuration.
5	bConfigurationValue	uint8_t	1	Number	Value to select this configuration with SetConfiguration().
6	iConfiguration	uint8_t	1	Index	Index of string descriptor describing this configuration.
7	bmAttributes	uint8_t	1	Bitmap	Configuration characteristics D7: Reserved (must be set to one for historical reasons) D6: Self-powered D5: Remote Wakeup D4...0: Reserved (reset to zero) A device configuration that uses power from the bus and a local source reports a non-zero value in bMaxPower to indicate the amount of bus power required and sets D6. The actual power source at runtime can be determined using the GetStatus(DEVICE) request. If a device configuration supports remote wakeup, D5 is set to 1.
8	bMaxPower	uint8_t	1	mA	Maximum power consumption of the USB device from the bus in this specific configuration when the device is fully operational. Expressed in 2mA units (i.e., 50 = 100mA).