Hi All,
I'm using NXP's SDK example project fatfs_usdcard. It does not seem to be working with 2gb SD cards. Others have posted similar issues with the LPC's SDK but there is no reported solution: https://community.nxp.com/thread/416897
The issue is not with the card, as multiples have been tried new out of box. And they function correctly in Windows.
Specifically, when issuing a f_mount() command it fails with FR_NO_FILESYSTEM. Drilling down further it is find_volume() that is unable to find a partition.
From find_volume():
/* Find an FAT partition on the drive. Supports only generic partitioning rules, FDISK and SFD. */
bsect = 0;
fmt = check_fs(fs, bsect); /* Load sector 0 and check if it is an FAT-VBR as SFD */
if (fmt == 2 || (fmt < 2 && LD2PT(vol) != 0)) { /* Not an FAT-VBR or forced partition number */
for (i = 0; i < 4; i++) { /* Get partition offset */
pt = fs->win + (MBR_Table + i * SZ_PTE);
br[i] = pt[PTE_System] ? ld_dword(pt + PTE_StLba) : 0;
}
i = LD2PT(vol); /* Partition number: 0:auto, 1-4:forced */
if (i != 0) i--;
do { /* Find an FAT volume */
bsect = br[i];
fmt = bsect ? check_fs(fs, bsect) : 3; /* Check the partition */
} while (LD2PT(vol) == 0 && fmt >= 2 && ++i < 4);
}
if (fmt == 4) return FR_DISK_ERR; /* An error occured in the disk I/O layer */
if (fmt >= 2) return FR_NO_FILESYSTEM; /* No FAT volume is found */
Drilling down further it is check_fs() that returns 2. Meaning it found a BS, but not a FAT one, despite there really being a FAT filesystem.
from check_fs()
if (fs->win[BS_JmpBoot] == 0xE9 || fs->win[BS_JmpBoot] == 0xEB || fs->win[BS_JmpBoot] == 0xE8) { /* Valid JumpBoot code? */
if (!mem_cmp(fs->win + BS_FilSysType, "FAT", 3)) return 0; /* Is it an FAT VBR? */
if (!mem_cmp(fs->win + BS_FilSysType32, "FAT32", 5)) return 0; /* Is it an FAT32 VBR? */
}
return 2; /* Valid BS but not FAT */
The bytes associated with the filesystem types are the index positions as follows:
#define BS_FilSysType 54 /* Filesystem type string (8-byte) */
#define BS_FilSysType32 82 /* FAT32: Filesystem type string (8-byte) */
However, when inspecting what fs->win contains at runtime these positions are 0s.
This issue does not occur when I move up to a 4GB SD card. And every great once in a while a 2GB card will return with a valid FAT. Indicating, perhaps, the issue doesn't lie with ff.c but the lower level NXP driver fetching bits via SPI ... ???
