EKS-LM4F232H5QD SD Card Seek to End of File

David Muller1

Hi there,

I'm developing with a EKS-LM4F232H5QD board. I'm trying to use the included SD card drivers to log data as my controller goes in and out of hibernation. I'd like to append data to the end of the file every time the controller wakes from hibernation. Ideally, I'd use f_lseek function (described in this api: http://elm-chan.org/fsw/ff/00index_e.html) to seek to the end of the file like:

//work area (file system object) for logical drivers
FATFS g_sFatFs;

//file object
FIL fileObject;

f_lseek(fileObject, f_size(fileObject));

The software included with my board/Stellaris does not include the f_size function call, however. Would a call like sizeof(fileObject) do the trick instead of the f_size function? I've thought of just saving the total bytes I've written to the file into EEPROM before I hibernate, and updating that value every time I write to the card. Is there a better way to be doing all this? Thanks!

-David

over 13 years ago

0 Stellaris Jordan over 13 years ago

TI__Intellectual 1185 points

Hey David,

If you take a look at the definition of the FIL structure, it should contain an fsize field that you can use for this.

Actually, I think the origin of this issue might stem from using the wrong documentation. If you take a look in your stellarisware install, there's a file named "00index_e.html" under third_party/fatfs/doc/ that is similar to the link you posted, but should match exactly the functions supported in the version of fatfs that shipped with your stellarisware installation. If you look at that document under the f_lseek section, the example block should look something more like:

// Move to offset of 5000 from top of the file.

res = f_lseek(&file, 5000);

// Forward 3000 bytes

res = f_lseek(&file, file.fptr + 3000);

// Rewind 2000 bytes (take care on overflow)

res = f_lseek(&file, file.fptr - 2000);

// Move to end of the file

res = f_lseek(&file, file.fsize);

As you can see, this uses the fsize field of the FIL structure, which is supported in the version of fatfs you have (or at least the one I have) as opposed to trying to use the f_size function, which isn't supported at this time.

Also, I should admit that I don't have a hardware setup up and running at the moment to test this. If the above suggestion doesn't work for you, let me know and I'll scrounge together the hardware necessary to recreate what you're seeing and get you a verified solution.

Hope this helps!

0 David Muller1 over 13 years ago in reply to Stellaris Jordan

Prodigy 220 points

This is very helpful, thank you! I was not aware of that documentation!

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EKS-LM4F232H5QD SD Card Seek to End of File