Altered the HID class driver to only try to construct at maximum one packet per USB frame, to reduce CPU usage.

LUFA/DoxygenPages/ChangeLog.txt

@@ -34,6 +34,7 @@
   *     having to reset the Mass Storage interface
   *   - USB_CONFIG_ATTR_BUSPOWERED constant renamed to USB_CONFIG_ATTR_RESERVED, as this was misnamed (thanks to NXP Semiconductors)
   *   - Reordered board name definition indexes so that a mispelled BOARD compile option will default to BOARD_USER rather than BOARD_USBKEY
+  *   - Altered the HID class driver to only try to construct at maximum one packet per USB frame, to reduce CPU usage
   *  - Library Applications:
   *   - Altered the Mass Storage Host LowLevel demo so that SCSI data STALLs from the attached device can be recovered from automatically without
   *     having to reset the Mass Storage interface

LUFA/Drivers/USB/Class/Device/HIDClassDevice.c

@@ -156,6 +156,9 @@ void HID_Device_USBTask(USB_ClassInfo_HID_Device_t* const HIDInterfaceInfo)
 	if (USB_DeviceState != DEVICE_STATE_Configured)
 	  return;
 
+	if (HIDInterfaceInfo->State.PrevFrameNum == USB_Device_GetFrameNumber())
+	  return;
+	  
 	Endpoint_SelectEndpoint(HIDInterfaceInfo->Config.ReportINEndpointNumber);
 
 	if (Endpoint_IsReadWriteAllowed())
@@ -190,6 +193,8 @@ void HID_Device_USBTask(USB_ClassInfo_HID_Device_t* const HIDInterfaceInfo)
 
 			Endpoint_ClearIN();
 		}
+		
+		HIDInterfaceInfo->State.PrevFrameNum = USB_Device_GetFrameNumber();
 	}
 }
 

LUFA/Drivers/USB/Class/Device/HIDClassDevice.h

@@ -113,6 +113,7 @@
 				struct
 				{
 					bool     UsingReportProtocol; /**< Indicates if the HID interface is set to Boot or Report protocol mode. */
+					uint16_t PrevFrameNum; /**< Frame number of the previous HID report packet opportunity. */
 					uint16_t IdleCount; /**< Report idle period, in milliseconds, set by the host. */
 					uint16_t IdleMSRemaining; /**< Total number of milliseconds remaining before the idle period elapsed - this
 											   *   should be decremented by the user application if non-zero each millisecond. */