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All,
According to the Keil website the FlashFS library supports the following SD memory cards:
"....and SD/MMC/SDHC Memory Cards."
I have a requirement for SDXC card support (>32GB). Does anybody know if this LIB is capable of supporting up to 2TB memory?
It seems to me that it would (except for maybe some 32 bit variable problems), because the addressing of SDHC is done by 512 byte 'units' to circumvent the addressing issues with earlier SDSC cards. This method suggets that for up to 2TB (current SDXC spec requirements) a 32 bit variable will suffice (ie: So 2TB : (2,199,023,255,552 / 512) = 4294967296 (-1) (0xFFFFFFFF) which fits in a UINT32).
Many thanks. -S
Well, library should not have a problem with card larger than 32 GB but other problems do arise.
SDHC generally has FAT32 as file system and it seems that SDXC specification forces that it has to use exFAT which is Microsoft proprietary extended FAT file system. Library does not support exFAT.
So in theory SDXC could be used with FAT32 on it but it is not according to standard then and Windows will probably refuse to work with SDXC card if it is not formatted with exFAT.
wild,
Thanks for your reply. I was familiar with the exFAT requirement, but you brought up a good point regarding Windows support issues. I found this link informative regarding Windows support:
rshullic.wordpress.com/.../
In the mean time, I am waiting on a 64GB SDXC card which I will try with the FlashFS library and my eval board.
Well my guess is that if you format card, on embedded to FAT32, Windows will be able to work with it, but obviously you will not be able to format SDXC on Windows 7 to anything other then exFAT.
Follow up FYI:
I have tested both a 32GB SDHC (1st test) card and a 64GB SDXC card (2nd test) on the FLASH FS library and it seems even though I formatted the 64GB with the /FAT32 option that it does NOT detect the proper size of the card when the DIR command is executed. The SDIO interface was used.
So, it seems that there IS a problem with any SD Card greater than 32GB with this library as it currently is written (the eval board and code used was out of the /Keil450/ARM/Boards/ST/STM3220G-EVAL\RL\FlashFS directory).
Here are the results:
+-----------------------------------------------------------------------+ | SD/MMC Card File Manipulation example | | command ------------------+ function ---------------------------------+ Cmd> dir File System Directory... TEST 31.890 01.01.2011 12:00 1 File(s) 31.890 bytes 31.906.988.032 bytes free. +-----------------------------------------------------------------------+ | SD/MMC Card File Manipulation example | | command ------------------+ function ---------------------------------+ Cmd> format /fat32 Format Flash Memory Card? [Y/N] Memory Card Formatted. Card Label is /fat32 Cmd> dir File System Directory... No files... 29.497.458.688 bytes free.