The f_chdir function changes the current directory of the logical drive.
FRESULT f_chdir ( const TCHAR* path /* [IN] Path name */ );
FR_OK, FR_DISK_ERR, FR_INT_ERR, FR_NOT_READY, FR_NO_PATH, FR_INVALID_NAME, FR_INVALID_DRIVE, FR_NOT_ENABLED, FR_NO_FILESYSTEM, FR_TIMEOUT, FR_NOT_ENOUGH_CORE
The f_chdir function changes the current directory of the logical drive. Also the current drive will be changed when FatFs is configured FF_STR_VOLUME_ID == 2 and an full path is specified. The current directory of each logical drive is set root directory on mount.
Note that the current directory is retained in the each filesystem object and the current drive is retained in a static variable, so that they also affect other tasks that use the file functions.
Available when FF_FS_RPATH >= 1.
    /* Set current direcoty of the current drive ("dir1" in the root directory) */
    f_chdir("/dir1");
    /* Set current direcoty of drive 2 (parent directory of current directory) */
    f_chdir("2:..");
    /* Set current direcoty of drive "sdcard" (FF_STR_VOLUME_ID == 1) */
    f_chdir("sdcard:/dir1");
    /* Set current direcoty of drive "flash" and set this drive current drive (FF_STR_VOLUME_ID == 2) */
    f_chdir("/flash/dir1");