The card is not MBR and file structures are miss-aligned. The mkfs.vfat command suggested by pylon is the worst case.
#SD FORMATTER FAT32 MAC OS X#
I don't have a machine with a new version of OS X so I can't be sure if Mac OS X still formats SD cards incorrectly. I have had OS X format an SD card GPT instead of MBR which is unusable on Arduino. Mac OS X adds lot of non-standard hidden files and directories. The SD standard is for an MBR volume so this is not strictly correct.
#SD FORMATTER FAT32 WINDOWS#
Windows 7/8 formats an erased SD as a super floppy but if you choose the correct cluster size, file structures are aligned well. Windows just cleans the card and preserves the correct SD format. Windows 7/8 does a good job of reformatting a healthy SD card. Here are results of using mkfs.vfat, the SD Association Formatter, and the SdFat formatter Formatted with suggested mkfs.vfat commandįreeSpace: 31907.12 MB (MB = 1,000,000 bytes)ĭata area is not aligned on flash erase boundaries!ĭownload and use formatter from Consumers | SD Association!įreeSpace: 31902.30 MB (MB = 1,000,000 bytes)įreeSpace: 31902.37 MB (MB = 1,000,000 bytes) I was able to access the standard as a consultant and implemented the SdFat formatter example according to this specification. Unfortunately the SD association's standard for formatting SD cards is only available to members. This is done by placing reserved blocks in the correct places in the file system. You can only depend on the SD association's formatter to place file structures correctly to line up with flash chip boundaries. Linux does not correctly format SD cards.
It will always produce the optimum format for your card. These are extreme cases but I do often see this type problem so please use this formatter SD Memory Card Formatter | SD Association. Maximum latency: 1920 usec, Minimum Latency: 80 usec, Avg Latency: 437 usec Maximum latency: 117636 usec, Minimum Latency: 84 usec, Avg Latency: 1113 usec Maximum latency: 1912 usec, Minimum Latency: 84 usec, Avg Latency: 265 usec Maximum latency: 58888 usec, Minimum Latency: 84 usec, Avg Latency: 273 usec
Write takes about four times longer with FAT32 and small clusters. Here are results running the SdFat bench sketch on this card. Same card formatted FAT32 with small clusters on Windows.įreeSpace: 2065.05 MB (MB = 1,000,000 bytes)
#SD FORMATTER FAT32 FREE#
See Free space counter is slow - #2 by fat16lib - Storage - Arduino Forum for more details on code.įreeSpace: 2093.32 MB (MB = 1,000,000 bytes) Time to determine free space with a properly formatted card using the SdInfo sketch. This type performance hit will also be true for seek. First is an extreme case for determining free space on an SD. Here are some examples that show what can happen. Always format SD cards using SD Formatter SD Memory Card Formatter | SD Association.
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