SDFileSystem functions and examples

Questions » SDFileSystem functions and examples

Paul Staron

10 years ago.

Is there any information and simple usage examples for all the functions of SDFileSystem. For instance how to use fseek(fp, 0, SEEK_SET), fseek(fp, 0, SEEK_END) etc. Can I read/write a chunk of data in the middle of a block or only append data. I want to set a pointer to a random position in a file and read 96 bytes into a container, how would I do this. Read a complete 12K file into a container, these kind a things. Simple quickie examples.

This is a list I found in the library, I think simple example code for these functions is what I'm looking for.

FatFs module application interface

FRESULT f_mount (BYTE, FATFS*);                     /* Mount/Unmount a logical drive */
FRESULT f_open (FIL*, const TCHAR*, BYTE);          /* Open or create a file */
FRESULT f_read (FIL*, void*, UINT, UINT*);          /* Read data from a file */
FRESULT f_lseek (FIL*, DWORD);                      /* Move file pointer of a file object */
FRESULT f_close (FIL*);                             /* Close an open file object */
FRESULT f_opendir (FATFS_DIR*, const TCHAR*);             /* Open an existing directory */
FRESULT f_readdir (FATFS_DIR*, FILINFO*);                 /* Read a directory item */
FRESULT f_stat (const TCHAR*, FILINFO*);            /* Get file status */
FRESULT f_write (FIL*, const void*, UINT, UINT*);   /* Write data to a file */
FRESULT f_getfree (const TCHAR*, DWORD*, FATFS**);  /* Get number of free clusters on the drive */
FRESULT f_truncate (FIL*);                          /* Truncate file */
FRESULT f_sync (FIL*);                              /* Flush cached data of a writing file */
FRESULT f_unlink (const TCHAR*);                    /* Delete an existing file or directory */
FRESULT f_mkdir (const TCHAR*);                     /* Create a new directory */
FRESULT f_chmod (const TCHAR*, BYTE, BYTE);         /* Change attribute of the file/dir */
FRESULT f_utime (const TCHAR*, const FILINFO*);     /* Change times-tamp of the file/dir */
FRESULT f_rename (const TCHAR*, const TCHAR*);      /* Rename/Move a file or directory */
FRESULT f_chdrive (BYTE);                           /* Change current drive */
FRESULT f_chdir (const TCHAR*);                     /* Change current directory */
FRESULT f_getcwd (TCHAR*, UINT);                    /* Get current directory */
FRESULT f_forward (FIL*, UINT(*)(const BYTE*,UINT), UINT, UINT*);   /* Forward data to the stream */
FRESULT f_mkfs (BYTE, BYTE, UINT);                  /* Create a file system on the drive */
FRESULT f_fdisk (BYTE, const DWORD[], void*);       /* Divide a physical drive into some partitions */
int f_putc (TCHAR, FIL*);                           /* Put a character to the file */
int f_puts (const TCHAR*, FIL*);                    /* Put a string to the file */
int f_printf (FIL*, const TCHAR*, ...);             /* Put a formatted string to the file */
TCHAR* f_gets (TCHAR*, int, FIL*);                  /* Get a string from the file */

edit.....

I have found this:

http://www.cplusplus.com/reference/clibrary/cstdio/

So unless there is any 'Mbed' information, this will have to do.

1 Answer

Neil Thiessen

10 years ago.

Basically, SDFileSystem is built on top of FATFileSystem which is built on top of FatFs. Those functions you found are part of FatFs, and FATFileSystem provides some C++ objects to glue them to the C stdio library using a retarget layer buried deep within the mbed library. Ideally you should be using the C stdio API, but in practice I've found it to be slow and a memory hog. As an alternative, you can use the C++ objects in FATFileSystem directly. There's no official documentation on these, but this program should get you started:

Import program SDFileSystem_HelloWorld

A simple serial test program for the re-written SDFileSystem library.

Accepted Answer

Cheers Neil.

posted by Paul Staron 06 May 2016

Paul Staron

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