Improve commenting of the Dataflash stub board driver file, to prevent...

Improve commenting of the Dataflash stub board driver file, to prevent confusion of what the dataflash selection masks need to be. Update stub driver to automatically interleave data between the chips if two Dataflash chips are present.

LUFA/DriverStubs/Dataflash.h

@@ -67,10 +67,10 @@
 			#define DATAFLASH_NO_CHIP                    DATAFLASH_CHIPCS_MASK
 
 			/** Mask for the first dataflash chip selected. */
-			#define DATAFLASH_CHIP1                      // TODO: Replace with mask to select the first Dataflash chip
+			#define DATAFLASH_CHIP1                      // TODO: Replace with mask to hold /CS of first Dataflash low, and all others high
 
 			/** Mask for the second dataflash chip selected. */
-			#define DATAFLASH_CHIP2                      // TODO: Replace with mask to select the second Dataflash chip, if available
+			#define DATAFLASH_CHIP2                      // TODO: Replace with mask to hold /CS of second Dataflash low, and all others high
 			
 			/** Internal main memory page size for the board's dataflash ICs. */
 			#define DATAFLASH_PAGE_SIZE                  // TODO: Replace with the page size for the Dataflash ICs
@@ -95,8 +95,14 @@
 				if (PageAddress >= (DATAFLASH_PAGES * DATAFLASH_TOTALCHIPS))
 				  return;
 
-				// TODO: If more than one dataflash chip, select the correct chip from the page address here
-				Dataflash_SelectChip(DATAFLASH_CHIP1);
+				#if (DATAFLASH_TOTALCHIPS == 2)
+					if (PageAddress & 0x01)
+					  Dataflash_SelectChip(DATAFLASH_CHIP2);
+					else
+					  Dataflash_SelectChip(DATAFLASH_CHIP1);
+				#else
+					Dataflash_SelectChip(DATAFLASH_CHIP1);
+				#endif
 			}
 
 			/** Sends a set of page and buffer address bytes to the currently selected dataflash IC, for use with
@@ -106,9 +112,11 @@
 			 *  \param[in] BufferByte   Address within the dataflash's buffer
 			 */
 			static inline void Dataflash_SendAddressBytes(uint16_t PageAddress, const uint16_t BufferByte)
-			{	
-				// TODO: If more than one dataflash chip, adjust absolute page address to be correct for the current chip,
-				//       also the shifts may need to be altered to suit the dataflash model being used				
+			{
+				#if (DATAFLASH_TOTALCHIPS == 2)
+					PageAddress >>= 1;
+				#endif
+				
 				Dataflash_SendByte(PageAddress >> 5);
 				Dataflash_SendByte((PageAddress << 3) | (BufferByte >> 8));
 				Dataflash_SendByte(BufferByte);