FAT12 & FAT16 implementation (problem:cant read the file

[iseron]

Hello.

Now i'm developing a routine to create a big .TXT file, in a datalogger mode, what use all the space available in a compact flash device.

My way to do the datalogger, is create a .TXT file then fill with data in the data sectors in continuous order.

So I'll take the FAT information from the sector 0 ( boot sector). With this i have cluster size, number of Fat copies, size in sector of each fat and the root directory size.

With this info, ill create an archive, pointing to cluster 2, with the size of the CF (actually a little less due the space ocupied by the fat structure).

Then, write a FAT with the secuential clusters until reach the size of this archive, finishing the FAT with an EOF or FFFFh.

At last the data begins to be saved in the data sector.

My big-only problem is:
I can see the file in windows but when i try to open a message of error i only have. I can't open the file.
With a program like WINHEX i can open the compactflash and see all the operations work correctly and teh data its saved.

Question:
The fat, need like a checksum or something like that for create a file which can be readed?

Anybody can explain me the typical errors developing this kind of software?

PS: ill read all the specs from the microsof paper and this very clear web site.FAT12 & FAT 16 ----> http://www.maverick-os.dk/FileSystemFormats/FAT12_FileSystem.html

Thanks!
Ignacio.

[Pete Smith]