FAT heuristics mean a disk as small as the one emulated in the incomplete Mass Storag...

[pub/USBasp.git] / Bootloaders / Incomplete / MassStorage / Lib / VirtualFAT.c

diff --git a/Bootloaders/Incomplete/MassStorage/Lib/VirtualFAT.c b/Bootloaders/Incomplete/MassStorage/Lib/VirtualFAT.c
index 7a248d8..b111a53 100644 (file)
--- a/Bootloaders/Incomplete/MassStorage/Lib/VirtualFAT.c
+++ b/Bootloaders/Incomplete/MassStorage/Lib/VirtualFAT.c
@@ -42,15 +42,15 @@ static const FATBootBlock_t BootBlock =
                .TotalSectors16          = LUN_MEDIA_BLOCKS,
                .MediaDescriptor         = 0xF8,
                .SectorsPerFAT           = 1,
-               .SectorsPerTrack         = 32,
-               .Heads                   = 64,
+               .SectorsPerTrack         = LUN_MEDIA_BLOCKS % 64,
+               .Heads                   = LUN_MEDIA_BLOCKS / 64,
                .HiddenSectors           = 0,
                .TotalSectors32          = 0,
                .PhysicalDriveNum        = 0,
                .ExtendedBootRecordSig   = 0x29,
                .VolumeSerialNumber      = 0x12345678,
                .VolumeLabel             = "LUFA BOOT  ",
-               .FilesystemIdentifier    = "FAT16   ",
+               .FilesystemIdentifier    = "FAT12   ",
                .BootstrapProgram        = {0},
                .MagicSignature          = 0xAA55,
        };
@@ -67,7 +67,6 @@ static FATDirectoryEntry_t FirmwareFileEntry =
                .FileSizeBytes   = 2049,
        };
 
-
 static void WriteBlock(uint16_t BlockNumber)
 {
        uint8_t BlockBuffer[512];
@@ -83,6 +82,23 @@ static void WriteBlock(uint16_t BlockNumber)
        // TODO: Write to FLASH
 }
 
+void WriteFAT12ClusterEntry(uint8_t* FATTable, uint8_t Index, uint16_t NextEntry)
+{
+       uint8_t StartOffset = ((uint16_t)Index * 3) / 2;
+
+       /* Check if the start of the entry is at an upper nibble of the byte */
+       if (((uint16_t)Index * 3) % 2)
+       {
+               FATTable[StartOffset]     |= ((NextEntry & 0x0F) << 4);
+               FATTable[StartOffset + 1]  =  (NextEntry >> 4);
+       }
+       else
+       {
+               FATTable[StartOffset]      =  NextEntry;
+               FATTable[StartOffset + 1]  = (NextEntry >> 8);
+       }
+}
+
 static void ReadBlock(uint16_t BlockNumber)
 {
        uint8_t BlockBuffer[512];
@@ -102,19 +118,17 @@ static void ReadBlock(uint16_t BlockNumber)
                        printf(" <F>\r\n");
 
                        /* Cluster 0: Media type/Reserved */
-                       ((uint16_t*)&BlockBuffer)[0] = 0xFF00 | BootBlock.MediaDescriptor;
+                       WriteFAT12ClusterEntry(BlockBuffer, 0, 0xF00 | BootBlock.MediaDescriptor);
 
                        /* Cluster 1: Reserved */
-                       ((uint16_t*)&BlockBuffer)[1] = 0xFFFF;
+                       WriteFAT12ClusterEntry(BlockBuffer, 1, 0xFFF);
 
                        /* Cluster 2 onwards: Cluster chain of FIRMWARE.BIN */
                        for (uint16_t i = 0; i < FILE_CLUSTERS(2049); i++)
-                       {
-                               ((uint16_t*)&BlockBuffer)[i + 2] = i + 3;
-                       }
+                         WriteFAT12ClusterEntry(BlockBuffer, i+2, i+3);
 
                        /* Mark last cluster as end of file */
-                       ((uint16_t*)&BlockBuffer)[FILE_CLUSTERS(2049) + 1] = 0xFFFF;
+                       WriteFAT12ClusterEntry(BlockBuffer, FILE_CLUSTERS(2049) + 1, 0xFFF);
                        break;
 
                case 3: