Paul Staron

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7 years, 11 months ago.

SDFileSystem functions and examples

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
7 years, 11 months 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 programSDFileSystem_HelloWorld

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

Last commit 29 Aug 2016 by Neil Thiessen

Accepted Answer

Cheers Neil.

posted by Paul Staron 06 May 2016