Added basic driver example use code to the library documentation.

Made the USARTStream global public and documented in the SerialStream module, allowing for the serial USART stream to be accessed via its handle rather than via the implicit stdout and stdin streams.

LUFA/Drivers/Peripheral/SerialStream.h

@@ -47,8 +47,24 @@
  *  \section Module Description
  *  Serial stream driver for the USART subsystem on supported USB AVRs. This makes use of the functions in the
  *  regular USART driver (see \ref Group_Serial), but allows the avr-libc standard stream functions (printf,
- *  puts, etc.) to work with the
- *  USART.
+ *  puts, etc.) to work with the USART. Upon configuration, this will redirect the standard input and output
+ *  streams to the USART.
+ *
+ *  <b>Example Usage:</b>
+ *  \code
+ *      // Initialise the Serial Stream driver before first use, with 9600 baud (and no double-speed mode)
+ *      SerialStream_Init(9600, false);
+ *
+ *      // Write a string to the USART via the implicit stdout stream
+ *      printf("Test String using stdout\r\n");
+ *
+ *      // Write a string to the USART via the explicit USART stream
+ *      fprintf(&USARTStream, "Test String using explicit stream handle\r\n");
+ * 
+ *      // Read in an integer from the USART using the implicit stdin stream
+ *      uint16_t TestValue;
+ *      scanf("%d", &TestValue);
+ *  \endcode
  *
  *  @{
  */
@@ -69,9 +85,6 @@
 
 	/* Private Interface - For use in library only: */
 	#if !defined(__DOXYGEN__)
-		/* External Variables: */
-			extern FILE USARTStream;
-
 		/* Function Prototypes: */
 		#if defined(__INCLUDE_FROM_SERIALSTREAM_C)
 			static int SerialStream_TxByte(char DataByte,
@@ -105,6 +118,13 @@
 				Serial_ShutDown();
 			}
 
+		/* External Variables: */
+			/** Named stream for the USART, once \ref SerialStream_Init() has been called. This may be used with the
+			 *  file based stream functions (fprintf, fscanf, etc.) that require a handle to the stream rather than
+			 *  using the stdin and stdout named streams.
+			 */
+			extern FILE USARTStream;
+
 	/* Disable C linkage for C++ Compilers: */
 		#if defined(__cplusplus)
 			}