as always, MS has patents for obvious things. Slightly bad news, fortunately VFAT or exFAT needed for Windows communication by via card only. So long file name support really do not have be realised if we count using card exlusively inside embedded system.
and yes, the file size in directory entries for files is needed because although we have a fixed amount of storage space allocated, the actual file will probably be smaller and hence we need to know where it actually ends.
Mark1200: yes, you are right, the first LFN entry is the one that immediately precedes the normal directory entry. The last one is the first that appears in the directory table and it has a specific bit in the sequence number that indicates that it's the last entry.
mharkins: It's hard to say if exFat will get widely adopted. For now, its adoption is slow, but with the Secure Digital Association adopting exFAT as its recommended file system for SDXC cards, it might become more widespread.
Altant: yes, NAND flashes have a spare area that can (and must...) be used for Error Correction Codes (ECC). Without those, you can expect your file system to become corrupted really fast. HDDS also have OOB storage for ECC, but that's all hidden by the controller.
srdmahesh: It would depend on your application, if you need to interoperate with a desktop PC either through a removable media or through USB Mass Storage Device Class, having FAT is certainly a good bet. If that's not required, FAT might still be a good choice since it's relatively lightweight. Also, some journaling add-ons can make it more reliable and protect it from unexpected power-losses on embedded systems where you're exposed to unexpected power-losses
The low level disk interfaces save track/sector and crc for each sector as part of the magnetic patterns, historically. So for data integrity, something like that would need to wrap the data when saved to EEPROM or Flash.
In our case, *CERTAIN MODELS* of USB sticks were indicating that they had finished writing before they actually had, so the power-cut that followed was causing the last several writes to not actually get committed to the Flash media inside the USB stick. This led to corrupted FAT32 file systems.
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