Add symbolic names for USB Device String Descriptors within the demos, applications and bootloaders.

Demos/Device/LowLevel/GenericHID/Descriptors.c

@@ -83,8 +83,8 @@ const USB_Descriptor_Device_t PROGMEM DeviceDescriptor =
 	.ProductID              = 0x204F,
 	.ReleaseNumber          = VERSION_BCD(00.01),
 
-	.ManufacturerStrIndex   = 0x01,
-	.ProductStrIndex        = 0x02,
+	.ManufacturerStrIndex   = STRING_ID_Manufacturer,
+	.ProductStrIndex        = STRING_ID_Product,
 	.SerialNumStrIndex      = NO_DESCRIPTOR,
 
 	.NumberOfConfigurations = FIXED_NUM_CONFIGURATIONS
@@ -222,15 +222,15 @@ uint16_t CALLBACK_USB_GetDescriptor(const uint16_t wValue,
 		case DTYPE_String:
 			switch (DescriptorNumber)
 			{
-				case 0x00:
+				case STRING_ID_Language:
 					Address = &LanguageString;
 					Size    = pgm_read_byte(&LanguageString.Header.Size);
 					break;
-				case 0x01:
+				case STRING_ID_Manufacturer:
 					Address = &ManufacturerString;
 					Size    = pgm_read_byte(&ManufacturerString.Header.Size);
 					break;
-				case 0x02:
+				case STRING_ID_Product:
 					Address = &ProductString;
 					Size    = pgm_read_byte(&ProductString.Header.Size);
 					break;

Demos/Device/LowLevel/GenericHID/Descriptors.h

@@ -42,7 +42,7 @@
 		#include <avr/pgmspace.h>
 
 		#include "Config/AppConfig.h"
-		
+
 	/* Type Defines: */
 		/** Type define for the device configuration descriptor structure. This must be defined in the
 		 *  application code, as the configuration descriptor contains several sub-descriptors which
@@ -59,6 +59,17 @@
 	        USB_Descriptor_Endpoint_t             HID_ReportOUTEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
+		 *  have a unique ID index associated with it, which can be used to refer to the string from
+		 *  other descriptors.
+		 */
+		enum StringDescriptors_t
+		{
+		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
+		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
+		    STRING_ID_Product       = 2, /**< Product string ID */
+		};
+
 	/* Macros: */
 		/** Endpoint address of the Generic HID reporting IN endpoint. */
 		#define GENERIC_IN_EPADDR         (ENDPOINT_DIR_IN  | 1)