SDCard and FatFS

Enable SDCard

The SDCard driver and FAT file system library can be enabled in the iDev project properties under the feature settings:

Properties -> Indel iDev -> Feature settings -> Library -> Enable SDCARD and FAT file system driver

FAT file system Usage

The functions are modelled after the standard's open/close/read/write/gets etc functions. However they all start with a 'f_' prefix to not get confusion with the internal system functions. Please see the FatFS documentation for a deeper explanation of the functions.

The documentation of the FAT library and its functions is available under FatFS

To use the FAT library include its header. It's not necessary to use the ifdef around it. However like that it's easier to disable the code if the application is also used on a target without an SDCard.

#ifdef INOS_FATFS
    #include <ff.h>
#endif

Example: Scan card content

This example walks through all directories and prints the found items.

#ifdef INOS_FATFS
FILINFO Finfo;
DWORD AccSize;              /* Work register for fs command */
WORD AccFiles, AccDirs;
 
FRESULT scan_files (
    char* path      /* Pointer to the working buffer with start path */
)
{
    DIR dirs;
    FRESULT fr;
    int i;
 
    fr = f_opendir(&dirs, path);
    if (fr == FR_OK) {
        while (((fr = f_readdir(&dirs, &Finfo)) == FR_OK) && Finfo.fname[0]) {
            if (Finfo.fattrib & AM_DIR) {
                AccDirs++;
                i = strlen(path);
                path[i] = '/'; strcpy(path+i+1, Finfo.fname);
                fr = scan_files(path);
                path[i] = 0;
                if (fr != FR_OK) break;
            } else {
                printf("%s/%s\n", path, Finfo.fname);
                AccFiles++;
                AccSize += Finfo.fsize;
            }
        }
    }
 
    return fr;
}
 
void FatFSEx1()
{
    FATFS FatFs;        /* FatFs work area needed for each volume */
    FIL Fil;            /* File object needed for each open file */
    UINT bw;
 
    f_mount(&FatFs, "", 0);     /* Give a work area to the default drive */
 
    AccSize = 0;                /* Work register for fs command */
    AccFiles = 0;
    AccDirs = 0;
    char pathbuffer[260];
    pathbuffer[0] = 0;
    scan_files(pathbuffer);
}
#endif

Example: Read a text file

This example opens a file for reading and dumps the text lines as eventlog traces.

#ifdef INOS_FATFS
void FatFSEx2()
{
    FATFS FatFs;        /* FatFs work area needed for each volume */
 
    f_mount(&FatFs, "", 0);     /* Give a work area to the default drive */
 
    FIL Fil;            /* File object needed for each open file */
 
    if (f_open(&Fil, "License.txt", FA_READ | FA_OPEN_EXISTING) == FR_OK) { /* Open a file */
        char buf[256];
        while (f_gets(buf, sizeof(buf), &Fil)) {
            printf(buf);
        }
        f_close(&Fil);                              /* Close the file */
    }
}
#endif

Example: Write a file

This example opens a file for writing and writes a string into it. The file can then be read on a normal computer with a card reader.

#ifdef INOS_FATFS
void FatFSEx3()
{
    FATFS FatFs;        /* FatFs work area needed for each volume */
 
    f_mount(&FatFs, "", 0);     /* Give a work area to the default drive */
 
    FIL Fil;            /* File object needed for each open file */
 
    if (f_open(&Fil, "newfile.txt", FA_WRITE | FA_CREATE_ALWAYS) == FR_OK) {    /* Create a file */
        f_write(&Fil, "It works!\r\n", 11, &bw);    /* Write data to the file */
        f_close(&Fil);                              /* Close the file */
        if (bw != 11) {
            // something wrong
        }
    }
}
#endif

More examples are in the FatFS documentation. See the application note, "Extended Use of FatFs API".