USB Host Device Interface Numbers 

This constant defines the maximum number of interface that the attached device can contain in order for the USB Host Layer to process the device. The device will be processed if it only contains less interfaces than the value of this constant.

#define USB_HOST_DEVICE_INTERFACES_NUMBER 

Supporting more interface per device required more processing time and data memory.

An attached device contains a configuration that contains 10 interfaces, but the USB_HOST_DEVICE_INTERFACES_NUMBER is set to 5. The device will not be processed by the Host Layer. A dual CDC device needs to be supported. This device will have 4 interfaces. The USB_HOST_DEVICE_INTERFACES_NUMBER constant should be atleast 4.