Windows XP Formatting SD Card through Windows XP

[ParagGupta]

Hi,

I am in the process of writing FAT16 compliant file system. I want to port it to SDCard, for this I am using 2GB SDCard(Sandisk). The basic formatting and writing data to the SDCard I am doing through windows(XP) only.

I am facing following issues-
1: Master Boot Record is missing and Partition Boot Record starts from zero sector.
2: Data file should start at the first sector of data area but doesn't starts there. Let me explain this-

I have read following values form Partiton Boot Record-
Bytes_per_sector = 512
Sectors_per_cluster = 64
Reserved_sectors = 2
Number_of_FAT_copies = 2
Maximum_Root_DIR_entries = 512
Sectors_per_FAT = 243

With the above information we can say that-
partition_start_sector = 0;
fat1_start_sector = 2; //partition_start_sector + Reserved_sectors
fat2_start_sector = 245; //fat1_start_sector + Sectors_per_FAT
rdir_start_sector = 488; //fat2_start_sector + Sectors_per_FAT
userdata_start_sec = 520; //rdir_start_sector + 32

As user data starts at 520th sector thus first file's data should at this sector, but instead of this first file's data is starting from 525th sector.

I am unable to figure out why this is starting after 5 sectors.

Thanks
Parag

 

[crazylegs]

You should always format SD cards in the device they are going to be used in or you will lose data through corruption..

Why do you need to format the card through windows..

 

[JaLing]

A load of math and info on FAT, limitations etc.
Skim to the bottom of it.
http://www.pcnineoneone.com/howto/filesystems1.html

 

[guest_9323wk]

Hi,

I also second what CL, has said the best way to format an SD Card is through the device its self. Often when you format through windows you will need to reformat the card again when you put it into the device.

 

[floppybootstomp]

Aye, I formatted my SD card in NTFS once and my camera wouldn't recognise it.

Turned out it only liked FAT32.

 

[muckshifter]

... it's the best "numbers game" ever constituted.

Nice link JaLing, I think you also read the "question" properly.


Can I point out folks, ParagGupta is in the process of writing FAT16 compliant file system, he is merely using the SDcard to port it. The "device" don't really exist, that's the way I read it.


You should try FAT, or, as they call it now, FAT12 ... now that was fun!!

 

[floppybootstomp]

... it's the best "numbers game" ever constituted.

Nice link JaLing, I think you also read the "question" properly.


Can I point out folks, ParagGupta is in the process of writing FAT16 compliant file system, he is merely using the SDcard to port it. The "device" don't really exist, that's the way I read it.


You should try FAT, or, as they call it now, FAT12 ... now that was fun!!

oops

That'll teach me to speed read...

 

[ParagGupta]

What my intention is formatting & loading files onto SDCard through windows then plugging same SDCard on some microcontroller and reading back files through my File System (off course in this case my file system code will be running from microcontroller).

I have verified the contents till rdir_start_sector through hex editor and all the things (FAT1/FAT2, RDIR) are starting at correct offset only user data is starting after 5 sectors (i.e. 525) from the actual one (i.e. 500).

 

[Nobody in particular]

Aye, I formatted my SD card in NTFS once and my camera wouldn't recognise it.

Turned out it only liked FAT32.

Aye, same thing happened to my MicroSD for my phone.

Weird stuff