Posted on October 12, 2015 at 18:10The computer/system not being able to ''read'' the card is a bit of a high level diagnosis. You'd need to dig a lot deeper into the file system structures and sector access level to make a real determination on the nature of the failure.
FAT is not a particularly FLASH friendly file system, it uses a lot of repetitive writing to specific areas of the media, and while mitigated by the micro-controller in the card. Can be further mitigated on the host side with caching and lazy-writers.
Do you have an error handling or retry code in disk access layer? Go flushing/removal handling?
Are there any mechanical, thermal or moisture issue with how the card is installed?
How fast are you clocking the interface? Placement of pull-up resistors? Using 4-bit mode? Observed bit error in the same bit positions in high/low 4-bit nibbles?
Waiting for DMA complete and FIFO to flush?
Pretty sure most code doesn't use CRC, you might need to add you own integrity checking.
Are the cards using SLC or MLC NAND?
Do you have an experiences with higher grade cards from SanDisk?
Stuff wears out, you'd probably need a method to identify failing cards, do fsck/chkdsk on the board, or be able to perform recovery/reformatting.
