Code:

PROGMEM const char usbDescriptorHidReport[34] = 
{   
   //[Endpoint 0] 
   0x06, 0xa0, 0xff, // USAGE_PAGE (Vendor Defined Page 1)
   0x09, 0x01,       // USAGE (Vendor Usage 1)
   0xa1, 0x01,       // COLLECTION (Application)

   //[Endpoint 1] Interrupt-In (used to send data to the host spontaneously)
   // Input Report (Host PC sends us data)
   0x09, 0x02,       // Usage ID - vendor defined usage2
   0x15, 0x00,       // Logical Minimum (0)
   0x26, 0xFF, 0x00, // Logical Maximum (255)
   0x75, 0x08,       // Report Size (8 bits)
   0x95, 0x08,       // Report Count (8 fields)
   0x81, 0x02,       // Input (Data, Variable, Absolute)

   //[Endpoint 2] Interrupt-Out (PC is sending US data)
   // Output Report (We send data to PC) 
   0x09, 0x03,       // Usage ID - vendor defined usage3
   0x15, 0x00,       // Logical Minimum (0)
   0x26, 0xFF, 0x00, // Logical Maximum (255)
   0x75, 0x08,       // Report Size (8 bits)
   0x95, 0x08,         // Report Count (8 fields) //change to 32?
   0x91, 0x02,       // Output (Data, Variable, Absolute)

   0xc0              // END_COLLECTION
};

//to do this you must set USB_CFG_DESCR_PROPS_CONFIGURATION in usbconfig.h
#define W(x) (x)&0xFF,(x)>>8
#define USB_CFG_RESERVED          0x80
#define USB_CFG_SELFPOWERED       0x40 //remove this for BusPowered devices
PROGMEM const char usbDescriptorConfiguration[41] = 
{
//Config
   9,      //bLength
   2,      //bDescriptorType   2=CONFIG
   W(41),   //wTotalLength   
   1,      //bNumInterfaces   
   1,      //bConfigurationValue 
   0,      //ConfigurationStrIndex
   (USB_CFG_RESERVED | USB_CFG_SELFPOWERED), //ConfigAttributes
   100/2,   //MaxPower (in 2 Milliampere)   100 mA
//HID_Interface
   9,      //bLength
   4,      //bDescriptorType   4=INTERFACE
   0,      //bInterfaceNumber
   0,      //bAlternateSetting
   2,      //bTotalEndpoints
   0x03,   //bInterfaceClass      HID_CSCP_HIDClass
   0x00,   //bInterfaceSubClass   HID_CSCP_NonBootSubclass
   0x00,   //bInterfaceProtocol   HID_CSCP_NonBootProtocol
   0,      //InterfaceStrIndex      0=NONE
//HID_GenericHID
   9,      //bLength
   0x21,   //bDescriptorType HID
   1,1,   //BCD representation of HID version
   0,      //target country code
   1,      //number of HID Report Descriptor infos to follow
   0x22,   //descriptor type: report
   W(34),   //total length of report descriptor
//HID_ReportIN_Endpoint
   7,      //Length
   0x05,   //bDescriptorType ENDPOINT
   0x81,   //bEndpointAddress   ENDPOINT_DIR_IN=0x80+1
   0x03,   //bmAttributes      INTERRUPT   //0x03|(0<<2)|(0<<4)
   W(8),   //wMaxPacketSize
   10,      //Polling Interval in ms (cannot be less than 10)
//HID_ReportOUT_Endpoint
   7,      //Length
   0x05,   //bDescriptorType ENDPOINT
   0x02,   //bEndpointAddress   ENDPOINT_DIR_IN=0x00+2
   0x03,   //bmAttributes      INTERRUPT   //0x03|(0<<2)|(0<<4)
   W(8),   //wMaxPacketSize
   10,      //Polling Interval in ms (cannot be less than 10)
};