The FatFs module is assuming following conditions on portability.
+
+
ANSI C
+The FatFs module is a middleware written in ANSI C (C89). There is no platform dependence, so long as the compiler is in compliance with ANSI C.
+
Size of integer types
+The FatFs module assumes that size of char/short/long are 8/16/32 bit and int is 16 or 32 bit. These correspondence are defined in integer.h. This will not be a problem on most compilers. When any conflict with existing definitions is occured, you must resolve it with care.
+
+
+
System organizations
+
The dependency diagram shown below is a typical configuration of the embedded system with FatFs module.
+
+
+
Which function is required?
+
You need to provide only low level disk I/O functions that required by FatFs module and nothing else. If a working disk module for the target is already existing, you need to write only glue functions to attach it to the FatFs module. If not, you need to port any other disk module or write it from scratch. Most of defined functions are not that always required. For example, disk write function is not required in read-only configuration. Following table shows which function is required depends on configuration options.
+
+
Function
Required when:
Note
+
disk_initialize disk_status disk_read
Always
Disk I/O functions. Samples available in ffsample.zip. There are many implementations on the web.
O/S dependent functions. Samples available in option/syscall.c.
+
ff_mem_alloc ff_mem_free
_USE_LFN == 3
+
+
+
+
+
Limits
+
+
FAT sub-types: FAT12, FAT16 and FAT32.
+
Number of open files: Unlimited, depends on available memory.
+
Number of volumes: Upto 10.
+
File size: Depends on FAT specs. (upto 4G-1 bytes)
+
Volume size: Depends on FAT specs. (upto 2T bytes at 512 bytes/sector)
+
Cluster size: Depends on FAT specs. (upto 64K bytes at 512 bytes/sector)
+
Sector size: Depends on FAT specs. (upto 4K bytes)
+
+
+
+
+
Memory Usage
+
+
ARM7 32bit
ARM7 Thumb
CM3 Thumb-2
AVR
H8/300H
PIC24
RL78
V850ES
SH-2A
RX600
IA-32
+
Compiler
GCC
GCC
GCC
GCC
CH38
C30
CC78K0R
CA850
SHC
RXC
VC6
+
_WORD_ACCESS
0
0
0
1
0
0
0
1
0
1
1
+
+
text (Full, R/W)
10591
7119
6565
13240
10864
11619
13192
8031
8960
5977
7856
+
text (Min, R/W)
6671
4595
4293
8512
7232
7674
9033
5235
5768
3923
5129
+
text (Full, R/O)
4695
3121
2861
6218
5162
5466
6418
3799
3964
2847
3687
+
text (Min, R/O)
3523
2463
2275
4558
4058
4212
4948
2959
3096
2199
2857
+
bss
V*4 + 2
V*4 + 2
V*4 + 2
V*2 + 2
V*4 + 2
V*2 + 2
V*2 + 2
V*4 + 2
V*4 + 2
V*4 + 2
V*4 + 2
+
Work area (_FS_TINY == 0)
V*560 + F*550
V*560 + F*550
V*560 + F*550
V*560 + F*544
V*560 + F*550
V*560 + F*544
V*560 + F*544
V*560 + F*544
V*560 + F*550
V*560 + F*550
V*560 + F*550
+
Work area (_FS_TINY == 1)
V*560 + F*36
V*560 + F*36
V*560 + F*36
V*560 + F*32
V*560 + F*36
V*560 + F*32
V*560 + F*32
V*560 + F*36
V*560 + F*36
V*560 + F*36
V*560 + F*36
+
+
These are the memory usage on some target systems with following condition. The memory sizes are in unit of byte, V denotes number of volumes and F denotes number of open files. All samples are optimezed in code size.
Follwing table shows which API function is removed by configuration options for the module size reduction.
+
+
Function
_FS_MINIMIZE
_FS_READONLY
_USE_STRFUNC
_FS_RPATH
_FS_LABEL
_USE_MKFS
_USE_FORWARD
_MULTI_PARTITION
+
0
1
2
3
0
1
0
1/2
0
1
2
0
1
0
1
0
1
0
1
+
f_mount
+
f_open
+
f_close
+
f_read
+
f_write
x
+
f_sync
x
+
f_lseek
x
+
f_opendir
x
x
+
f_closedir
x
x
+
f_readdir
x
x
+
f_stat
x
x
x
+
f_getfree
x
x
x
x
+
f_truncate
x
x
x
x
+
f_unlink
x
x
x
x
+
f_mkdir
x
x
x
x
+
f_chmod
x
x
x
x
+
f_utime
x
x
x
x
+
f_rename
x
x
x
x
+
f_chdir
x
+
f_chdrive
x
+
f_getcwd
x
x
+
f_getlabel
x
+
f_setlabel
x
x
+
f_forward
x
+
f_mkfs
x
x
+
f_fdisk
x
x
x
+
f_putc
x
x
+
f_puts
x
x
+
f_printf
x
x
+
f_gets
x
+
+
+
+
+
Long File Name
+
The FatFs module has started to support long file name (LFN) at revision 0.07. The two different file names, SFN and LFN, of a file is transparent in the file functions except for f_readdir function. To enable LFN feature, set _USE_LFN to 1, 2 or 3, and add a Unicode code conversion function ff_convert() and ff_wtoupper() to the project. The LFN feature requiers a certain working buffer in addition. The buffer size can be configured by _MAX_LFN corresponding to the available memory size. The size of long file name will reach up to 255 characters, so that the _MAX_LFN should be set to 255 for full featured LFN operation. If the size of working buffer is insufficient for the given file name, the file function fails with FR_INVALID_NAME. When enable the LFN feature with re-entrant feature, _USE_LFN must be set to 2 or 3. In this case, the file function allocates the working buffer on the stack or heap. The working buffer occupies (_MAX_LFN + 1) * 2 bytes.
+
+
LFN cfg on ARM7TDMI
+
Code page
Program size
+
SBCS
+3.7K
+
932(Shift-JIS)
+62K
+
936(GBK)
+177K
+
949(Korean)
+139K
+
950(Big5)
+111K
+
+
When the LFN feature is enabled, the module size will be increased depends on the selected code page. Right table shows how many bytes increased when LFN feature is enabled with some code pages. Especially, in the CJK region, tens of thousands of characters are being used. Unfortunately, it requires a huge OEM-Unicode bidirectional conversion table and the module size will be drastically increased that shown in the table. As the result, the FatFs with LFN feature with those code pages will not able to be implemented to most 8-bit microcontrollers.
+
Note that the LFN feature on the FAT file system is a patent of Microsoft Corporation. This is not the case on FAT32 but most FAT32 drivers come with the LFN feature. FatFs can swich the LFN feature off by configuration option. When enable LFN feature on the commercial products, a license from Microsoft may be required depends on the final destination.
+
+
+
+
Unicode API
+
By default, FatFs uses ANSI/OEM code set on the API under LFN configuration. FatFs can also switch the character encoding to Unicode on the API (_LFN_UNICODE). This means the FatFs supports the True-LFN feature. For more information, refer to the description in the file name.
+
+
+
+
Re-entrancy
+
The file operations to the different volume is always re-entrant and can work simultaneously. The file operations to the same volume is not re-entrant but it can also be configured to thread-safe with _FS_REENTRANT option. In this case, also the OS dependent synchronization object control functions, ff_cre_syncobj(), ff_del_syncobj(), ff_req_grant() and ff_rel_grant() must be added to the project.
+
When a file function is called while the volume is in use by any other task, the file function is suspended until that task leaves file function. If wait time exceeded a period defined by _TIMEOUT, the file function will abort with FR_TIMEOUT. The timeout feature might not be supported by some RTOS.
+
There is an exception for f_mount(), f_mkfs(), f_fdisk() function. These functions are not re-entrant to the same volume or corresponding physical drive. When use these functions, all other tasks must unmount the volume and avoid to access the volume.
+
Note that this section describes on the re-entrancy of the FatFs module itself but also the low level disk I/O layer will need to be re-entrant.
+
+
+
+
Duplicated File Access
+
FatFs module does not support the shareing controls of duplicated file access in default. It is permitted when open method to a file is only read mode. The duplicated open in write mode to a file is always prohibited and open file must not be renamed, deleted, or the FAT structure on the volume can be collapted.
+
The file shareing control can also be available when _FS_LOCK is set to 1 or grater. The value specifies the number of files to manage simultaneously. In this case, if any open, rename or remove that violating the file shareing rule that described above is attempted, the file function will fail with FR_LOCKED. If number of open objects gets larger than _FS_LOCK, the f_open()/f_opendir() function will fail with FR_TOO_MANY_OPEN_FILES.
+
+
+
+
Performance Effective File Access
+
For good performance to read/write files on the small embedded system, application programmer should consider what process is done in the FatFs module. The file data on the volume is transferred in following sequence by f_read() function.
+
Figure 1. Sector miss-aligned read (short)
+
+
+
Figure 2. Sector miss-aligned read (long)
+
+
+
Figure 3. Sector aligned read
+
+
+
The file I/O buffer is a sector buffer to read/write a partial data on the sector. The sector buffer is either file private sector buffer on each file object or shared sector buffer in the file system object. The buffer configuration option _FS_TINY determins which sector buffer is used for the file data transfer. When tiny buffer (1) is selected, data memory consumption is reduced 512 bytes each file object. In this case, FatFs module uses only a sector buffer in the file system object for file data transfer and FAT/directory access. The disadvantage of the tiny buffer configuration is: the FAT data cached in the sector buffer will be lost by file data transfer and it must be reloaded at every cluster boundary. However it will be suitable for most application from view point of the decent performance and low memory comsumption.
+
Figure 1 shows that a partial sector, sector mis-aligned part of the file, is transferred via the file I/O buffer. On long data transfer shown in Figure 2, middle of transfer data that covers one or more sector is transferred to the application buffer directly. Figure 3 shows that the case of entier transfer data is aligned to the sector boundary. In this case, file I/O buffer is not used. On the direct transfer, the maximum extent of sectors are read with disk_read() function at a time but the multiple sector transfer never across the cluster boundary even if it is contiguous.
+
Therefore taking effort to sector aligned read/write accesss avoids buffered data transfer and the read/write performance will be improved. Besides the effect, cached FAT data will not be flushed by file data transfer at the tiny configuration, so that it can achieve same performance as non-tiny configuration with small memory footprint.
+
+
+
+
Considerations on Flash Memory Media
+
To maximize the write performance of flash memory media, such as SDC and CFC, it must be controlled in consideration of its characteristitcs.
+
Using Mutiple-Sector Write
+
+Figure 6. Comparison between Multiple/Single Sector Write
+
+
+
The write throughput of the flash memory media becomes the worst at single sector write and it increases proportional to the number of sectors per a write transaction. This effect more appers at more fast bus clock and its ratio often becomes grater than ten. The number of write transaction also affects the life time of the media. Therefore the application program should write the data in large block as possible. The ideal block size is cluster size or power of 2 bytes and the byte offset should be aligned to the block. Of course all layers between the application and the media must support multiple sector write feature, however most of open-source disk drivers lack it. Do not split a multiple sector write request into single sector writes or the write throughput gets poor. Note that FatFs module and its sample disk drivers supprt multiple sector read/write feature.
+
Forcing Memory Erase
+
When remove a file with f_remove() function, the data clusters occupied by the file are marked 'free' on the FAT. But the data sectors containing the file data are not that applied any process, so that the file data left occupies a part of the flash memory array as 'live block'. If the file data is forced erased on removing the file, the number of free blocks on the flash memory will be increased. This may skip internal block erase operation to the data block on next write. As the result the write performance might be improved. To enable this feature, set _USE_ERASE to 1. Note that this is a feature with expectation of internal process of the flash memory media. It may not always effective and f_remove() function will take a time to remove a large file. Most applications will not need this feature.
+
+
+
+
Critical Section
+
If a write operation to the FAT volume is interrupted due to any accidental failure, such as sudden blackout, incorrect disk removal and unrecoverable disk error, the FAT structure on the volume can be collapted. Following images shows the critical section of the FatFs module.
+
+Figure 4. Long critical section
+
+
+
+Figure 5. Minimized critical section
+
+
+
+
An interruption in the red section can cause a cross link; as a result, the object being changed can be lost. If an interruption in the yellow section is occured, there is one or more possibility listed below.
+
+
The file data being rewrited is collapted.
+
The file being appended returns initial state.
+
The file created as new is gone.
+
The file created as new or overwritten remains but no content.
+
Efficiency of disk use gets worse due to lost clusters.
+
+
Each case does not affect the files that not opened in write mode. To minimize risk of data loss, the critical section can be minimized by minimizing the time that file is opened in write mode or using f_sync() function as shown in Figure 5.
+
+
+
+
Extended Use of APIs
+
These are examples of extended use of FatFs APIs. New item will be added whenever a useful code is found.
This is a copy of the FatFs license document that included in the source codes.
+
/*----------------------------------------------------------------------------/
+/ FatFs - FAT file system module R0.10 (C)ChaN, 2013
+/-----------------------------------------------------------------------------/
+/ FatFs module is a generic FAT file system module for small embedded systems.
+/ This is a free software that opened for education, research and commercial
+/ developments under license policy of following trems.
+/
+/ Copyright (C) 2013, ChaN, all right reserved.
+/
+/ * The FatFs module is a free software and there is NO WARRANTY.
+/ * No restriction on use. You can use, modify and redistribute it for
+/ personal, non-profit or commercial products UNDER YOUR RESPONSIBILITY.
+/ * Redistributions of source code must retain the above copyright notice.
+/
+/-----------------------------------------------------------------------------/
+
Therefore FatFs license is one of the BSD-style license but there is a significant feature. Because FatFs is for embedded projects, the conditions for redistributions in binary form, such as embedded code, hex file and binary library, are not specified to increase its usability. The documentation of the distributions need not include about FatFs and its license document, and it may also. This is equivalent to the BSD 1-Clause License. Of course FatFs is compatible with the projects under GNU GPL. When redistribute the FatFs with any modification, the license can also be changed to GNU GPL or BSD-style license.
The f_chdir() function changes the current directory of the logical drive. The current directory of a drive is initialized to the root directory when the drive is auto-mounted. Note that the current directory is retained in the each file system object so that it also affects other tasks that using the volume.
+
+
+
+
+
QuickInfo
+
Available when _FS_RPATH >= 1.
+
+
+
+
+
Example
+
+ /* Change current direcoty of the current drive (dir1 under root dir) */
+ f_chdir("/dir1");
+
+ /* Change current direcoty of drive 2 (parent dir) */
+ f_chdir("2:..");
+
The f_chdrive() function changes the current drive. The initial value of the current drive number is 0. Note that the current drive is retained in a static variable so that it also affects other tasks that using the file functions.
The f_close() function closes an open file object. If any data has been written to the file, the cached information of the file is written back to the volume. After the function succeeded, the file object is no longer valid and it can be discarded.
+
Note that if the file object is in read-only mode and _FS_LOCK option is not enabled, the file object can also be discarded without this process. However it is not recommended for future compatibility.
The f_closedir() function closes an open directory object. After the function succeeded, the file object is no longer valid and it can be discarded.
+
Note that the directory object can also be discarded without this process unless _FS_LOCK option is not enabled. However it is not recommended for future compatibility.
Specifies the physical drive number to initialize.
+
+
+
+
+
+
Return Values
+
This function returns a disk status as the result. For details of the disk status, refer to the disk_status() function.
+
+
+
+
Description
+
This function initializes a physical drive and put it ready to generic read/write data. When the function succeeded, STA_NOINIT flag in the return value is cleared.
+
Application program MUST NOT call this function while FatFs is in use, or FAT structure on the volume can be corrapted. To re-initialize the file system, use f_mount() function instead. This function is called on volume mount process by FatFs module to manage the media change.
The disk_ioctl function cntrols device specific features and miscellaneous functions other than generic read/write.
+
+DRESULT disk_ioctl (
+ BYTE pdrv, /* [IN] Drive number */
+ BYTE cmd, /* [IN] Control command code */
+ void* buff/* [I/O] Parameter and data buffer */
+);
+
+
+
+
+
Parameters
+
+
pdrv
+
Specifies the drive number (0-9).
+
cmd
+
Specifies the command code.
+
buff
+
Pointer to the parameter buffer depends on the command code. Set NULL if not used.
+
+
+
+
+
+
Return Value
+
+
RES_OK (0)
+
The function succeeded.
+
RES_ERROR
+
Any error occured.
+
RES_PARERR
+
Invalid command code or parameter.
+
RES_NOTRDY
+
The disk drive has not been initialized.
+
+
+
+
+
+
Description
+
The FatFs module uses only device independent commands described below. Any device dependent function is not used.
+
+
Command
Description
+
CTRL_SYNC
Make sure that the disk drive has finished pending write process. When the disk I/O module has a write back cache, flush the dirty sector immediately. This command is not used in read-only configuration.
+
GET_SECTOR_SIZE
Returns sector size of the drive into the WORD variable pointed by buff. This command is not used in fixed sector size configuration, _MAX_SS is 512.
+
GET_SECTOR_COUNT
Returns number of available sectors on the drive into the DWORD variable pointed by buff. This command is used by only f_mkfs() function to determine the volume size to be created.
+
GET_BLOCK_SIZE
Returns erase block size of the flash memory in unit of sector into the DWORD variable pointed by buff. The allowable value is 1 to 32768 in power of 2. Return 1 if the erase block size is unknown or disk devices. This command is used by only f_mkfs() function and it attempts to align data area to the erase block boundary.
+
CTRL_ERASE_SECTOR
Erases a part of the flash memory specified by a DWORD array {<start sector>, <end sector>} pointed by buff. This is similar command to Trim command of ATA command set. When this feature is not supported or not a flash memory media, this command has no effect. The FatFs does not check the result code and the file function is not affected even if the sectors are not erased well. This command is called on removing a cluster chain when _USE_ERASE is 1.
The disk_read function reads sector(s) from the disk drive.
+
+DRESULT disk_read (
+ BYTE pdrv, /* [IN] Physical drive number */
+ BYTE* buff, /* [OUT] Pointer to the read data buffer */
+ DWORD sector, /* [IN] Start sector number */
+ UINT count/* [IN] Number of sectros to read */
+);
+
+
+
+
+
Parameters
+
+
pdrv
+
Specifies the physical drive number.
+
buff
+
Pointer to the byte array to store the read data. The size of buffer must be in sector size * sector count.
+
sector
+
Specifies the start sector number in logical block address (LBA).
+
count
+
Specifies number of sectors to read. FatFs specifis with 1 to 128. Generally, a multiple sector transfer request must not be split into single sector transactions to the device, or you may not get good read performance.
+
+
+
+
+
+
Return Value
+
+
RES_OK (0)
+
The function succeeded.
+
RES_ERROR
+
Any hard error occured during the read operation and could not recover it.
+
RES_PARERR
+
Invalid parameter.
+
RES_NOTRDY
+
The disk drive has not been initialized.
+
+
+
+
+
+
Description
+
The memory address specified by buff is not that always aligned to word boundary because the type of argument is defined as BYTE*. The misaligned read/write request can occure at direct transfer. If the bus architecture, especially DMA controller, does not allow misaligned memory access, it should be solved in this function. There are some workarounds described below to avoid this issue.
+
+
Convert word transfer to byte transfer in this function. - Recommended.
+
For f_read(), avoid long read request that includes a whole of sector. - Direct transfer will never occure.
+
For f_read(fp, buff, btr, &br), make sure that (((UINT)buff & 3) == (f_tell(fp) & 3)) is true. - Word aligned direct transfer is guaranteed.
Specifies the physical drive number to be confirmed.
+
+
+
+
+
+
Return Values
+
The disk status is returned in combination of following flags. FatFs refers only STA_NOINIT and STA_PROTECTED.
+
+
STA_NOINIT
+
Indicates that the disk drive is not initialized. This flag is set on system reset, media removal or failure of disk_initialize() function. It is cleared on disk_initialize() function succeeded. Media change that occurs asynchronously must be captured and reflect it to the status flags, or auto-mount feature will not work correctly. When media change detection feature is not supported, application program needs to de-initialize the file system object with f_mount() function after the media change.
+
STA_NODISK
+
Indicates that no medium in the drive. This is always cleared on fixed disk drive. Note that FatFs does not refer this flag.
+
STA_PROTECTED
+
Indicates that the medium is write protected. This is always cleared on the drive that does not support write protect notch. Not valid while no medium in the drive.
+DRESULT disk_write (
+ BYTE drv, /* [IN] Physical drive number */
+ const BYTE* buff, /* [IN] Write data (may be non aligned) */
+ DWORD sector, /* [IN] Sector number to write */
+ UINT count/* [IN] Number of sectors to write */
+);
+
+
+
+
+
Parameters
+
+
pdrv
+
Specifies the physical drive number.
+
buff
+
Pointer to the byte array to be written.
+
sector
+
Specifies the start sector number in logical block address (LBA).
+
count
+
Specifies the number of sectors to write. FatFs specifis 1 to 128. Generally, a multiple sector transfer request must not be split into single sector transactions to the device, or you will never get good write performance.
+
+
+
+
+
+
Return Values
+
+
RES_OK (0)
+
The function succeeded.
+
RES_ERROR
+
Any hard error occured during the write operation and could not recover it.
+
RES_WRPRT
+
The medium is write protected.
+
RES_PARERR
+
Invalid parameter.
+
RES_NOTRDY
+
The disk drive has not been initialized.
+
+
+
+
+
+
Description
+
This function is not required in read only configuration. The specified memory address is not that always aligned to word boundary because the type of pointer is defined as BYTE. For more information, read description in disk_read function.
+
Application program MUST NOT call this function while FatFs is in use, or FAT structure on the volume can be corrapted.
Currnet time is returned with packed into a DWORD value. The bit field is as follows:
+
+
bit31:25
+
Year from 1980 (0..127)
+
bit24:21
+
Month (1..12)
+
bit20:16
+
Day in month(1..31)
+
bit15:11
+
Hour (0..23)
+
bit10:5
+
Minute (0..59)
+
bit4:0
+
Second / 2 (0..29)
+
+
+
+
+
+
Description
+
The get_fattime() function must return any valid time even if the system does not support a real time clock. If a zero is returned, the file will not have a valid time. This fucntion is not required in read only configuration.
The f_fdisk() function creates a partition table into the MBR of the physical drive. The partitioning rule is in generic FDISK format, so that it can create upto four primary partitions. Extended partition is not supported. The part[] array with four items specifies how to divide the physical drive. The first item specifies the size of first primary partition and fourth item specifies the fourth primary partition. If the value is less than or equal to 100, it means percentage of the partition in the entire disk space. If it is larger than 100, it means partition size in unit of sector.
+
+
+
+
QuickInfo
+
Available when _FS_READOLNY == 0, _USE_MKFS == 1 and _MULTI_PARTITION == 1.
+ /* Initialize a brand-new disk drive mapped to physical drive 0 */
+
+ FATFS fs;
+ DWORD plist[] = {50, 50, 0, 0}; /* Divide drive into two partitions */
+ BYTE work[_MAX_SS];
+
+ f_fdisk(0, plist, work); /* Divide physical drive 0 */
+
+ f_mount(&fs, "0:", 0); /* Register work area to the logical drive 0 */
+ f_mkfs("0:", 0, 0); /* Create FAT volume on the logical drive 0. 2nd argument is ignored. */
+ f_mount(0, "0:", 0); /* Unregister work area from the logical drive 0 */
+
+ f_mount(&fs, "1:", 0); /* Give a work area to the logical drive 1 */
+ f_mkfs("1:", 0, 0); /* Create FAT volume on the logical drive 1. 2nd argument is ignored. */
+ f_mount(0, "1:", 0); /* Unregister work area from the logical drive 1 */
+
+
The format of path name on the FatFs module is similer to the filename specs of DOS/Windos as follows:
+
"[drive#:][/]directory/file"
+
The FatFs module supports long file name (LFN) and 8.3 format file name (SFN). The LFN can be used when LFN feature is enabled (_USE_LFN > 0). The sub directories are separated with a \ or / in the same way as DOS/Windows API. Duplicated separators are skipped and ignored. Only a difference is that the logical drive is specified in a numeral with a colon. When the drive number is omitted, it is assumed as default drive (drive 0 or current drive).
+
Control characters ('\0' to '\x1F') are recognized as end of the path name. Leading/embedded spaces in the path name are valid as a part of the name at LFN configuration but they are recognized as end of the path name at non-LFN configuration. Trailing spaces and dots are ignored.
+
In default configuration (_FS_RPATH == 0), it does not have a concept of current directory like OS oriented file system. All objects on the volume are always specified in full path name that follows from the root directory. Dot directory names are not allowed. Heading separator is ignored and it can be exist or omitted. The default drive number is fixed to 0.
+
When relative path feature is enabled (_FS_RPATH == 1), specified path is followed from the root directory if a heading separator is exist. If not, it is followed from the current directory set with f_chdir function. Dot names are also allowed for the path name. The default drive is the current drive set with f_chdrive function.
+
+
Path name
_FS_RPATH == 0
_FS_RPATH == 1
+
file.txt
A file in the root directory of the drive 0
A file in the current directory of the current drive
+
/file.txt
A file in the root directory of the drive 0
A file in the root directory of the current drive
+
The root directory of the drive 0
The current directory of the current drive
+
/
The root directory of the drive 0
The root directory of the current drive
+
2:
The root directory of the drive 2
The current directory of the drive 2
+
2:/
The root directory of the drive 2
The root directory of the drive 2
+
2:file.txt
A file in the root directory of the drive 2
A file in the current directory of the drive 2
+
../file.txt
Invalid name
A file in the parent directory
+
.
Invalid name
This directory
+
..
Invalid name
Parent directory of the current directory
+
dir1/..
Invalid name
The current directory
+
/..
Invalid name
The root directory (sticks the top level)
+
+
+
+
+
+
Unicode API
+
The path names are input/output in either ANSI/OEM code (SBCS/DBCS) or Unicode depends on the configuration options. The type of arguments which specify the file names are defined as TCHAR. It is an alias of char in default. The code set used to the file name string is ANSI/OEM specifid by _CODE_PAGE. When _LFN_UNICODE is set to 1, the type of the TCHAR is switched to WCHAR to support Unicode (UTF-16 encoding). In this case, the LFN feature is fully supported and the Unicode specific characters, such as ✝☪✡☸☭, can also be used for the path name. It also affects data types and encoding of the string I/O functions. To define literal strings, _T(s) and _TEXT(s) macro are available to select either ANSI/OEM or Unicode automatically. The code shown below is an example to define the literal strings.
The FatFs module needs dynamic work area called file system object for each volume (logical drive). It is registered to the FatFs module by f_mount() function. By default, each logical drive is bound to the physical drive with the same drive number and an FAT volume on the drive is serched by auto detect feature. It loads boot sectors and checks it if it is an FAT boot sector in order of sector 0 as SFD format, 1st partition, 2nd partition, 3rd partition and 4th partition as FDISK format.
+
When _MULTI_PARTITION == 1 is specified by configuration option, each individual logical drive is bound to the partition on the physical drive specified by volume management table. The volume management table must be defined by user to resolve relationship between logical drives and partitions. Following code is an example of a volume management table.
+
+Example: Logical drive 0-2 are tied to three pri-partitions on the physical drive 0 (fixed disk)
+ Logical drive 3 is tied to an FAT volume on the physical drive 1 (removable disk)
+
+PARTITION VolToPart[] = {
+ {0, 1}, /* Logical drive 0 ==> Physical drive 0, 1st partition */
+ {0, 2}, /* Logical drive 1 ==> Physical drive 0, 2nd partition */
+ {0, 3}, /* Logical drive 2 ==> Physical drive 0, 3rd partition */
+ {1, 0} /* Logical drive 3 ==> Physical drive 1 (auto detection) */
+};
+
+
+
There are some considerations on using _MULTI_PARTITION configuration.
+
+
Only four primary partitions can be specified. Logical partition is not supported.
+
The physical drive that has two or more partitions must be non-removable class.
The f_forward() function reads the data from the file and forward it to the outgoing stream without data buffer. This is suitable for small memory system because it does not require any data buffer at application module. The file pointer of the file object increases in number of bytes forwarded. In case of *bf is less than btf without error, it means the requested bytes could not be transferred due to end of file or stream goes busy during data transfer.
+
+
+
+
+
QuickInfo
+
Available when _USE_FORWARD == 1 and _FS_TINY == 1.
+
+
+
+
+
Example (Audio playback)
+
+/*------------------------------------------------------------------------*/
+/* Sample code of data transfer function to be called back from f_forward */
+/*------------------------------------------------------------------------*/
+
+UINT out_stream ( /* Returns number of bytes sent or stream status */
+ const BYTE *p, /* Pointer to the data block to be sent */
+ UINT btf /* >0: Transfer call (Number of bytes to be sent). 0: Sense call */
+)
+{
+ UINT cnt = 0;
+
+
+ if (btf == 0) { /* Sense call */
+ /* Return stream status (0: Busy, 1: Ready) */
+ /* When once it returned ready to sense call, it must accept a byte at least */
+ /* at subsequent transfer call, or f_forward will fail with FR_INT_ERR. */
+ if (FIFO_READY) cnt = 1;
+ }
+ else { /* Transfer call */
+ do { /* Repeat while there is any data to be sent and the stream is ready */
+ FIFO_PORT = *p++;
+ cnt++;
+ } while (cnt < btf && FIFO_READY);
+ }
+
+ return cnt;
+}
+
+
+/*------------------------------------------------------------------------*/
+/* Sample code using f_forward function */
+/*------------------------------------------------------------------------*/
+
+FRESULT play_file (
+ char *fn /* Pointer to the audio file name to be played */
+)
+{
+ FRESULT rc;
+ FIL fil;
+ UINT dmy;
+
+ /* Open the audio file in read only mode */
+ rc = f_open(&fil, fn, FA_READ);
+ if (rc) return rc;
+
+ /* Repeat until the file pointer reaches end of the file */
+ while (rc == FR_OK && fil.fptr < fil.fsize) {
+
+ /* any other processes... */
+
+ /* Fill output stream periodicaly or on-demand */
+ rc = f_forward(&fil, out_stream, 1000, &dmy);
+ }
+
+ /* Close the file and return */
+ f_close(&fil);
+ return rc;
+}
+
The f_getcwd() function retrieves full path name of the current directory of the current drive. When _VOLUMES is larger than 1, a logical drive number is added to top of the path name.
The f_getfree() function gets number of free clusters on the volume. The member csize in the file system object indicates number of sectors per cluster, so that the free space in unit of sector can be calcurated with this information. When FSINFO structure on the FAT32 volume is not in sync, this function can return an incorrect free cluster count. To avoid this problem, FatFs can be forced full FAT scan by _FS_NOFSINFO option.
+
+
+
+
+
QuickInfo
+
Available when _FS_READONLY == 0 and _FS_MINIMIZE == 0.
+
+
+
+
+
Example
+
+ FATFS *fs;
+ DWORD fre_clust, fre_sect, tot_sect;
+
+
+ /* Get volume information and free clusters of drive 1 */
+ res = f_getfree("1:", &fre_clust, &fs);
+ if (res) die(res);
+
+ /* Get total sectors and free sectors */
+ tot_sect = (fs->n_fatent - 2) * fs->csize;
+ fre_sect = fre_clust * fs->csize;
+
+ /* Print the free space (assuming 512 bytes/sector) */
+ printf("%10lu KiB total drive space.\n%10lu KiB available.\n",
+ tot_sect / 2, fre_sect / 2);
+
The f_getlabel function returns volume label and volume serial number of a drive.
+
+FRESULT f_getlabel (
+ const TCHAR* path, /* [IN] Drive number */
+ TCHAR* buff, /* [OUT] Volume label */
+ DWORD* sn/* [OUT] Volume serial number */
+);
+
+
+
+
+
Parameters
+
+
path
+
Pointer to the null-terminated string that specifies the logical drive. Null-string specifies the default drive.
+
buff
+
Pointer to the buffer to store the volume label. The buffer size must be at least 12 items. If the volume has no label, a null-string will be returned. Set null pointer if this information is not needed.
+
sn
+
Pointer to the DWORD variable to store the volume serial number. Set null pointer if this information is not needed.
When the function succeeded, buff will be returuned.
+
+
+
+
+
Description
+
The f_gets() function is a wrapper function of f_read() function. The read operation continues until a '\n' is stored, reached end of the file or the buffer is filled with len - 1 characters. The read string is terminated with a '\0'. When no character to read or any error occured during read operation, it returns a null pointer. The status of EOF and error can be examined with f_eof() and f_error() macros.
+
When FatFs is configured to Unicode API (_LFN_UNICODE == 1), data types on the srting fuctions, f_putc(), f_puts(), f_printf() and f_gets(), is also switched to Unicode. The character encoding on the file to be read/written via those functions is selected by _STRF_ENCODE option.
+
+
+
+
+
QuickInfo
+
Available when _USE_STRFUNC is 1 or 2. When it is set to 2, '\r's contained in the file are stripped out.
The f_lseek() function moves the file read/write pointer of an open file. The offset can be specified in only origin from top of the file. When an offset beyond the file size is specified in write mode, the file size is expanded to the specified offset. The file data in the expanded area is undefined because no data is written to the file. This is suitable to pre-allocate a cluster chain quickly, for fast write operation. After the f_lseek() function succeeded, the current read/write pointer should be checked in order to make sure the read/write pointer has been moved correctry. In case of the current read/write pointer is not the expected value, either of followings has been occured.
+
+
End of file. The specified ofs was clipped at end of the file because the file has been opened in read-only mode.
+
Disk full. There is insufficient free space on the volume to expand the file.
+
+
Fast seek feature is enabled when _USE_FASTSEEK is set to 1 and the member cltbl in the file object is not NULL. This feature enables fast backward/long seek operations without FAT access by using cluster link map table (CLMT). It is also applied to f_read()/f_write() function. In this mode, the file cannot be expanded by f_write()/f_lseek() function.
+
The CLMT must be created in the user defined DWORD array prior to use the fast seek feature. To create the CLMT, set address of the DWORD array to the member cltbl in the file object, set the array size in unit of items into the first item and call the f_lseek() function with ofs = CREATE_LINKMAP. After the function succeeded and CLMT is created, no FAT access is occured in subsequent f_read()/f_write()/f_lseek() function to the file. If the function failed with FR_NOT_ENOUGH_CORE, the given array size is insufficient for the file and number of items required is returned into the first item of the array. The required array size is (number of fragments + 1) * 2 items. For example, when the file is fragmented in 5, 12 items will be required for the CLMT.
+
+
+
+
+
QuickInfo
+
Available when _FS_MINIMIZE <= 2.
+
+
+
+
+
Example
+
+ /* Open file */
+ fp = malloc(sizeof (FIL));
+ res = f_open(fp, "file.dat", FA_READ|FA_WRITE);
+ if (res) ...
+
+ /* Move to offset of 5000 from top of the file */
+ res = f_lseek(fp, 5000);
+
+ /* Move to end of the file to append data */
+ res = f_lseek(fp, f_size(fp));
+
+ /* Forward 3000 bytes */
+ res = f_lseek(fp, f_tell(fp) + 3000);
+
+ /* Rewind 2000 bytes (take care on wraparound) */
+ res = f_lseek(fp, f_tell(fp) - 2000);
+
+
+/* Cluster pre-allocation (to prevent buffer overrun on streaming write) */
+
+ res = f_open(fp, recfile, FA_CREATE_NEW | FA_WRITE); /* Create a file */
+
+ res = f_lseek(fp, PRE_SIZE); /* Expand file size (cluster pre-allocation) */
+ if (res || f_tell(fp) != PRE_SIZE) ... /* Check if the file has been expanded */
+
+ res = f_lseek(fp, DATA_START); /* Record data stream WITHOUT cluster allocation delay */
+ ... /* DATA_START and write block size should be aligned to sector boundary */
+
+ res = f_truncate(fp); /* Truncate unused area */
+ res = f_lseek(fp, 0); /* Put file header */
+ ...
+
+ res = f_close(fp);
+
+
+/* Using fast seek feature */
+
+ DWORD clmt[SZ_TBL]; /* Cluster link map table buffer */
+
+ res = f_lseek(fp, ofs1); /* This is normal seek (cltbl member is nulled on file open) */
+
+ fp->cltbl = clmt; /* Enable fast seek feature */
+ clmt[0] = SZ_TBL; /* Set table size */
+ res = f_lseek(fp, CREATE_LINKMAP); /* Create CLMT */
+ ...
+
+ res = f_lseek(fp, ofs2); /* This is fast seek */
+
Available when _FS_READONLY == 0 and _FS_MINIMIZE == 0.
+
+
+
+
+
Example
+
+ res = f_mkdir("sub1");
+ if (res) die(res);
+ res = f_mkdir("sub1/sub2");
+ if (res) die(res);
+ res = f_mkdir("sub1/sub2/sub3");
+ if (res) die(res);
+
The f_mkfs fucntion creates an FAT file system on the logical drive.
+
+FRESULT f_mkfs (
+ const TCHAR* path, /* [IN] Logical drive number */
+ BYTE sfd, /* [IN] Partitioning rule */
+ UINT au/* [IN] Size of the allocation unit */
+);
+
+
+
+
+
Parameters
+
+
path
+
Pinter to the null-terminated string that specifies the logical drive to be formatted. If there is no drive number, it means the default drive.
+
sfd
+
Specifies partitioning rule (FDISK(0) or SFD(1)). This argument will be ignored on some case.
+
au
+
Specifies size of the allocation unit (cluter) in unit of byte. The value must be sector size * n (n is 1 to 128 and power of 2). When a zero is given, the cluster size is determined depends on the volume size.
The f_mkfs() function creates an FAT volume on the logical drive. When FDISK format is specified, a primary partition occupies the entire disk space is created and then an FAT volume is created on the partition. When SFD format is specified, the FAT volume starts from the first sector of the physical drive.
+
If the logical drive has been bound to any partition (1-4) by multiple partition feature (_MULTI_PARTITION), the FAT volume is created into the specified partition. In this case, the second argument sfd is ignored. The physical drive must have been partitioned with f_fdisk() function or any other partitioning tool prior to use this function.
+
Note that there are two partitioning rules, FDISK and SFD. The FDISK partitioning is usually used for harddisk, MMC, SDC, CFC and U Disk. It can divide a physical drive into one or more partitions with a partition table on the MBR. However Windows does not support multiple partition on the removable media. The SFD is non-partitioned method. The FAT volume starts from the first sector on the physical drive without partition table. It is usually used for floppy disk, Microdrive, optical disk and super-floppy media.
+
The FAT sub-type, FAT12/FAT16/FAT32, is determined by number of clusters on the volume and nothing else, according to the FAT specification issued by Microsoft. Thus which FAT sub-type is selected, is depends on the volume size and the specified cluster size. The cluster size affects performance of the file system and large cluster increases the performance.
+
When the number of clusters gets near the FAT sub-type boundaries, the function can fail with FR_MKFS_ABORTED.
+
+
+
+
QuickInfo
+
Available when _FS_READOLNY == 0 and _USE_MKFS == 1.
The f_mount() function registers/unregisters a file system object used for the logical drive to the FatFs module as follows:
+
+
Determines the logical drive which specified by path.
+
Clears and unregisters the regsitered work area of the drive.
+
Clears and registers the work area to the drive if fatfs is not NULL.
+
Performs volume mount process to the drive if forced mount is specified.
+
+
The file system object is the work area needed for each logical drive. It must be given to the logical drive with this function prior to use any other file functions. To unregister a work area, specify a NULL to the fatfs, and then the work area can be discarded.
+
If forced mount is not specified, this function always succeeds regardless of the physical drive status due to delayed mount feature. It only clears (de-initializes) the given work area and registers its address to the internal table. No activity of the physical drive in this function. It can also be used to force de-initialized the registered work area of a logical drive. The volume mount processes, initialize the corresponding physical drive, find the FAT volume in it and initialize the work area, is performed in the subsequent file access functions when either or both of following condition is true.
+
+
File system object is not initialized. It is cleared by f_mount().
+
Physical drive is not initialized. It is de-initialized by system reset or media removal.
+
+
If the function with forced mount failed, it means that the file system object is registered but the volume is currently not available. Mount process will also be attempted in subsequent file access functions.
+
If implementation of the disk I/O layer lacks media change detection, application program needs to perform a f_mount() after media change to force cleared the file system object.
After f_open() function succeeded, the file object is valid. The file object is used for subsequent read/write functions to identify the file. To close an open file, use f_close() function. If the file is modified and not closed properly, the file data will be collapted.
+
If duplicated file open is needed, read here carefully. However duplicated open of a file with write mode flag is always prohibited.
+
Before using any file function, a work area (file system object) must be registered to the logical drive with f_mount() function. All API functions except for f_fdisk() function can work after this procedure.
+
+
+
+
+
QuickInfo
+
Always available. The mode flags, FA_WRITE, FA_CREATE_ALWAYS, FA_CREATE_NEW and FA_OPEN_ALWAYS, are not available when _FS_READONLY == 1.
+
+
+
+
+
Example
+
+/* Read a text file and display it */
+
+FATFS FatFs; /* Work area (file system object) for logical drive */
+
+int main (void)
+{
+ FIL fil; /* File object */
+ char line[82]; /* Line buffer */
+ FRESULT fr; /* FatFs return code */
+
+
+ /* Register work area to the default drive */
+ f_mount(&FatFs, "", 0);
+
+ /* Open a text file */
+ fr = f_open(&fil, "message.txt", FA_READ);
+ if (fr) return (int)fr;
+
+ /* Read all lines and display it */
+ while (f_gets(line, sizeof line, &fil))
+ printf(line);
+
+ /* Close the file */
+ f_close(&fil);
+
+ return 0;
+}
+
+
+/* Copy a file "file.bin" on the drive 1 to drive 0 */
+
+int main (void)
+{
+ FATFS fs[2]; /* Work area (file system object) for logical drives */
+ FIL fsrc, fdst; /* File objects */
+ BYTE buffer[4096]; /* File copy buffer */
+ FRESULT fr; /* FatFs function common result code */
+ UINT br, bw; /* File read/write count */
+
+
+ /* Register work area for each logical drive */
+ f_mount(&fs[0], "0:", 0);
+ f_mount(&fs[1], "1:", 0);
+
+ /* Open source file on the drive 1 */
+ fr = f_open(&fsrc, "1:file.bin", FA_OPEN_EXISTING | FA_READ);
+ if (fr) return (int)fr;
+
+ /* Create destination file on the drive 0 */
+ fr = f_open(&fdst, "0:file.bin", FA_CREATE_ALWAYS | FA_WRITE);
+ if (fr) return (int)fr;
+
+ /* Copy source to destination */
+ for (;;) {
+ fr = f_read(&fsrc, buffer, sizeof buffer, &br); /* Read a chunk of source file */
+ if (fr || br == 0) break; /* error or eof */
+ fr = f_write(&fdst, buffer, br, &bw); /* Write it to the destination file */
+ if (fr || bw < br) break; /* error or disk full */
+ }
+
+ /* Close open files */
+ f_close(&fsrc);
+ f_close(&fdst);
+
+ /* Unregister work area prior to discard it */
+ f_mount(NULL, "0:", 0);
+ f_mount(NULL, "1:", 0);
+
+ return (int)fr;
+}
+
When the function succeeded, it returns number of characters written. When the function failed due to disk full or any error, an EOF (-1) will be returned.
+
+
+
+
+
Description
+
The f_printf() is a wrapper function of f_write(). The format control directive is a sub-set of standard library shown as follos:
+
+
Type: c C s S d D u U x X b B
+
Size: l L
+
Flag: 0 -
+
+
+
+
+
+
QuickInfo
+
Available when _FS_READONLY == 0 and _USE_STRFUNC is 1 or 2. When it is set to 2, '\n's contained in the output are converted to "\r\n".
+
When FatFs is configured to Unicode API (_LFN_UNICODE == 1), data types on the srting fuctions, f_putc(), f_puts(), f_printf() and f_gets(), is also switched to Unicode. The character encoding on the file to be read/written via those functions is selected by _STRF_ENCODE option.
+int f_putc (
+ TCHAR chr, /* [IN] A character to put */
+ FIL* fp/* [IN] File object */
+);
+
+
+
+
+
Parameters
+
+
chr
+
A character to be put.
+
fp
+
Pointer to the open file object structuer.
+
+
+
+
+
+
Return Values
+
When the character was written successfuly, it returns number of characters written. When the function failed due to disk full or any error, an EOF (-1) will be returned.
+
When FatFs is configured to Unicode API (_LFN_UNICODE == 1), character encoding on the string fuctions, f_putc(), f_puts(), f_printf() and f_gets(), is also switched to Unicode. The character encoding on the file to be read/written via those functions is selected by _STRF_ENCODE option.
+
+
+
+
+
Description
+
The f_putc() function is a wrapper function of f_write() function.
+
+
+
+
+
QuickInfo
+
Available when _FS_READONLY == 0 and _USE_STRFUNC is 1 or 2. When it is set to 2, a '\n' is converted to "\r\n".
Pointer to the null terminated string to be written. The null character will not be written.
+
fp
+
Pointer to the open file object structure.
+
+
+
+
+
+
Return Value
+
When the function succeeded, it returns number of characters written. When the write operation is aborted due to disk full or any error, an EOF (-1) will be returned.
+
When FatFs is configured to Unicode API (_LFN_UNICODE == 1), character encoding on the srting fuctions, f_putc(), f_puts(), f_printf() and f_gets(), is also switched to Unicode. The character encoding on the file to be read/written via those functions is selected by _STRF_ENCODE option.
+
+
+
+
+
Description
+
The f_puts() function is a wrapper function of f_write() function.
+
+
+
+
+
QuickInfo
+
Available when _FS_READONLY == 0 and _USE_STRFUNC is 1 or 2. When it is set to 2, '\n's contained in the string are converted to "\r\n".
On the FatFs API, most of file functions return common result code as enum type FRESULT. When a function succeeded, it returns zero, otherwise returns non-zero value that indicates type of error.
+
+
+
FR_OK (0)
+
The function succeeded.
+
FR_DISK_ERR
+
An unrecoverable error occured in the lower layer, disk_read(), disk_write() or disk_ioctl() function.
+
FR_INT_ERR
+
Assertion failed. An insanity is detected in the internal process. One of the following possibilities are suspected.
+
+
There is any error of the FAT structure on the volume.
+
Work area (file system object, file object or etc...) is broken by stack overflow or any other application. This is the reason in most case.
+
An FR_DISK_ERR has occured on the file object.
+
+
+
FR_NOT_READY
+
The disk drive cannot work due to incorrect medium removal or disk_initialize() function failed.
The file read/write pointer of the file object advances number of bytes read. After the function succeeded, *br should be checked to detect the end of file. In case of *br is less than btr, it means the read/write pointer reached end of the file during read operation.
The f_readdir() function reads directory items, file and directory, in sequence. All items in the directory can be read by calling f_readdir() function repeatedly. When relative path feature is enabled (_FS_RPATH >= 1), dot entries ("." and "..") are not filtered out and they will appear in the read items. When all directory items have been read and no item to read, a null string is returned into the fname[] without any error. When a null pointer is given to the fno, the read index of the directory object is rewinded.
+
When LFN feature is enabled, lfname and lfsize in the file information structure must be initialized with valid value prior to use it. The lfname is a pointer to the LFN read buffer. The lfsize is size of the LFN read buffer in unit of TCHAR. If the LFN is not needed, set a null pointer to the lfname and the LFN is not returned. A null string will be returned into the LFN read buffer in case of following conditions.
+
+
The directory item has no LFN information.
+
Either the size of read buffer or LFN working buffer is insufficient for the LFN.
+
The LFN contains Unicode charactrer that cannot be converted to OEM code. (not the case on Unicode API)
+
+
When the directory item has no LFN information, lower case characters can be contained in the fname[].
+
+
+
+
+
QuickInfo
+
Available when _FS_MINIMIZE <= 1.
+
+
+
+
+
Sample Code
+
+FRESULT scan_files (
+ char* path /* Start node to be scanned (also used as work area) */
+)
+{
+ FRESULT res;
+ FILINFO fno;
+ DIR dir;
+ int i;
+ char *fn; /* This function is assuming non-Unicode cfg. */
+#if _USE_LFN
+ static char lfn[_MAX_LFN + 1]; /* Buffer to store the LFN */
+ fno.lfname = lfn;
+ fno.lfsize = sizeof lfn;
+#endif
+
+
+ res = f_opendir(&dir, path); /* Open the directory */
+ if (res == FR_OK) {
+ i = strlen(path);
+ for (;;) {
+ res = f_readdir(&dir, &fno); /* Read a directory item */
+ if (res != FR_OK || fno.fname[0] == 0) break; /* Break on error or end of dir */
+ if (fno.fname[0] == '.') continue; /* Ignore dot entry */
+#if _USE_LFN
+ fn = *fno.lfname ? fno.lfname : fno.fname;
+#else
+ fn = fno.fname;
+#endif
+ if (fno.fattrib & AM_DIR) { /* It is a directory */
+ sprintf(&path[i], "/%s", fn);
+ res = scan_files(path);
+ if (res != FR_OK) break;
+ path[i] = 0;
+ } else { /* It is a file. */
+ printf("%s/%s\n", path, fn);
+ }
+ }
+ f_closedir(&dir)
+ }
+
+ return res;
+}
+
Renames a file or sub-directory and can also move it to other directory. The logical drive number is determined by old name, new name must not contain a logical drive number. Do not rename open objects or directry table can be collapted.
+
+
+
+
+
QuickInfo
+
Available when _FS_READONLY == 0 and _FS_MINIMIZE == 0.
+
+
+
+
+
Example
+
+ /* Rename an object */
+ f_rename("oldname.txt", "newname.txt");
+
+ /* Rename and move an object to other directory */
+ f_rename("oldname.txt", "dir1/newname.txt");
+
The DIR structure is used for the work area to read a directory by f_oepndir()/f_readdir() function. Application program must not modify any member in this structure.
+
+typedefstruct {
+ FATFS* fs; /* Pointer to the owner file system object */
+ WORD id; /* Owner file system mount ID */
+ WORD index; /* Index of directory entry to start to search next */
+ DWORD sclust; /* Table start cluster (0:Root directory) */
+ DWORD clust; /* Current cluster */
+ DWORD sect; /* Current sector */
+ BYTE* dir; /* Pointer to the current SFN entry in the win[] */
+ BYTE* fn; /* Pointer to the SFN (in/out) {file[8],ext[3],status[1]} */
+#if _FS_LOCK
+ UINT lockid; /* Sub-directory lock ID (0:Root directory) */
+#endif
+#if _USE_LFN
+ WCHAR* lfn; /* Pointer to the LFN working buffer */
+ WORD lfn_idx; /* Index of top of last matched LFN entris (0xFFFF:No LFN) */
+#endif
+} DIR;
+
When the string has a drive number, the volume label will be set to the volume specified by the drive number. If the volume label is a null-string, the volume label on the volume will be removed. The format of the volume label is similar to the SFN but there are some differences shown below:
+
+
11 bytes or less in length as local character code.
+
Cannot contain period.
+
Can contain spaces anywhere in the name.
+
+
+
+
+
QuickInfo
+
Available when _FS_READONLY == 0 and _USE_LABEL == 1.
+
+
+
+
+
Example
+
+ /* Set volume label to the default drive */
+ f_setlabel("DATA DISK");
+
+ /* Set volume label to the drive 2 */
+ f_setlabel("2:DISK 3 OF 4");
+
+ /* Remove volume label of the drive 2 */
+ f_setlabel("2:");
+
The FATFS structure (file system object) holds dynamic work area of individual logical drives. It is given by application program and registerd/unregisterd to the FatFs module with f_mount() function. Initialization is done on first API call after f_mount() function or media change. Application program must not modify any member in this structure.
+
+typedefstruct {
+ BYTE fs_type; /* FAT sub-type (0:Not mounted) */
+ BYTE drv; /* Physical drive number */
+ BYTE csize; /* Sectors per cluster (1,2,4,...,128) */
+ BYTE n_fats; /* Number of FAT copies (1,2) */
+ BYTE wflag; /* win[] flag (b0:win[] is dirty) */
+ BYTE fsi_flag; /* FSINFO flags (b7:Disabled, b0:Dirty) */
+ WORD id; /* File system mount ID */
+ WORD n_rootdir; /* Number of root directory entries (FAT12/16) */
+#if _MAX_SS != 512
+ WORD ssize; /* Sector size (512,1024,2048 or 4096) */
+#endif
+#if _FS_REENTRANT
+ _SYNC_t sobj; /* Identifier of sync object */
+#endif
+#if !_FS_READONLY
+ DWORD last_clust; /* FSINFO: Last allocated cluster */
+ DWORD free_clust; /* FSINFO: Number of free clusters */
+#endif
+#if _FS_RPATH
+ DWORD cdir; /* Current directory start cluster (0:root) */
+#endif
+ DWORD n_fatent; /* Number of FAT entries (== Number of clusters + 2) */
+ DWORD fsize; /* Sectors per FAT */
+ DWORD volbase; /* Volume start sector */
+ DWORD fatbase; /* FAT area start sector */
+ DWORD dirbase; /* Root directory area start sector (FAT32: Cluster#) */
+ DWORD database; /* Data area start sector */
+ DWORD winsect; /* Current sector appearing in the win[] */
+ BYTE win[_MAX_SS]; /* Disk access window for directory, FAT (and file data at tiny cfg) */
+} FATFS;
+
The FIL structure (file object) holds state of an open file. It is created by f_open() function and discarded by f_close() function. Application program must not modify any member in this structure except for cltbl. Note that a sector buffer is defined in this structure at non-tiny configuration, so that the FIL structures should not be defined as auto variable.
+
+
+typedefstruct {
+ FATFS* fs; /* Pointer to the owner file system object */
+ WORD id; /* Owner file system mount ID */
+ BYTE flag; /* File object status flags */
+ BYTE err; /* Abort flag (error code) */
+ DWORD fptr; /* File read/write pointer (Byte offset origin from top of the file) */
+ DWORD fsize; /* File size in unit of byte */
+ DWORD sclust; /* File start cluster */
+ DWORD clust; /* Current cluster */
+ DWORD dsect; /* Current data sector */
+#if !_FS_READONLY
+ DWORD dir_sect; /* Sector containing the directory entry */
+ BYTE* dir_ptr; /* Ponter to the directory entry in the window */
+#endif
+#if _USE_FASTSEEK
+ DWORD* cltbl; /* Pointer to the cluster link map table (Nulled on file open) */
+#endif
+#if _FS_LOCK
+ UINT lockid; /* Fle lock ID */
+#endif
+#if !_FS_TINY
+ BYTE buf[_MAX_SS]; /* File private data transfer buffer */
+#endif
+} FIL;
+
The FILINFO structure holds a file information returned by f_readdir() and f_stat() function.
+
+typedef struct {
+ DWORD fsize; /* File size */
+ WORD fdate; /* Last modified date */
+ WORD ftime; /* Last modified time */
+ BYTE fattrib; /* Attribute */
+ TCHAR fname[13]; /* Short file name (8.3 format) */
+#if _USE_LFN
+ TCHAR* lfname; /* Pointer to the LFN buffer */
+ int lfsize; /* Size of the LFN buffer in unit of TCHAR */
+#endif
+} FILINFO;
+
+
+
+
Members
+
+
fsize
+
Indicates size of the file in unit of byte. Always zero for directories.
+
fdate
+
Indicates the date that the file was modified or the directory was created.
+
+
bit15:9
+
Year origin from 1980 (0..127)
+
bit8:5
+
Month (1..12)
+
bit4:0
+
Day (1..31)
+
+
+
ftime
+
Indicates the time that the file was modified or the directory was created.
+
+
bit15:11
+
Hour (0..23)
+
bit10:5
+
Minute (0..59)
+
bit4:0
+
Second / 2 (0..29)
+
+
+
fattrib
+
Indicates the file/directory attribute in combination of AM_DIR, AM_RDO, AM_HID, AM_SYS and AM_ARC.
+
fname[]
+
Indicates the file/directory name in 8.3 format null-terminated string. It is always returnd with upper case in non-LFN configuration but it can be returned with lower case in LFN configuration.
+
lfname
+
Pointer to the LFN buffer to store the read LFN. This member must be initialized by application prior to use this structure. Not available in non-LFN configuration.
+
lfsize
+
Size of the LFN buffer in unit of TCHAR. This member must be initialized by application prior to use this structure. Not available in non-LFN configuration.
The f_stat() function checks the existence of a file or sub-directory. If exist, the function returns with FR_OK and the information of the object is stored to the file information structure. If not exist, the function returns with FR_NO_FILE. For details, refer to the FILINFO structure and f_readdir() function.
The f_sync() function performs the same process as f_close() function but the file is left opened and can continue read/write/seek operations to the file. This is suitable for the applications that open files for a long time in write mode, such as data logger. Performing f_sync() function of periodic or immediataly after f_write() function can minimize the risk of data loss due to a sudden blackout or an unintentional media removal. For more information, refer to application note.
+
However the f_sync() function immediataly before f_close() function has no advantage because it performs f_sync() function in it. In other words, the differnce between those functions is that the file object is invalidated or not.
The f_truncate() function truncates the file size to the current file read/write pointer. This function has no effect if the file read/write pointer is already pointing end of the file.
+
+
+
+
+
QuickInfo
+
Available when _FS_READONLY == 0 and _FS_MINIMIZE == 0.
+If condition of the object to be removed is applicable to the following terms, the function will be rejected.
+
The object must not have read-only attribute (AM_RDO) or the function will be rejected with FR_DENIED.
+
The sub-directory must be empty and must not be current directory or the function will be rejected with FR_DENIED.
+
The file or directory must not have been opened or the FAT volume can be collapted. It will able to be rejected with FR_LOCKED when file lock feature is enabled.
+
+
+
+
+
+
QuickInfo
+
Available when _FS_READONLY == 0 and _FS_MINIMIZE == 0.
+FRESULT f_write (
+ FIL* fp, /* [IN] Pointer to the file object structure */
+ const void* buff, /* [IN] Pointer to the data to be written */
+ UINT btw, /* [IN] Number of bytes to write */
+ UINT* bw/* [OUT] Pointer to the variable to return number of bytes written */
+);
+
+
+
+
+
Parameters
+
+
fp
+
Pointer to the open file object structure.
+
buff
+
Pointer to the data to be written.
+
btw
+
Specifies number of bytes to write in range of UINT type.
+
bw
+
Pointer to the UINT variable to return the number of bytes written. The value is always valid after the function call regardless of the result.
The read/write pointer of the file object advances number of bytes written. After the function succeeded, *bw should be checked to detect the disk full. In case of *bw is less than btw, it means the volume got full during the write operation. The function can take a time when the volume is full or close to full.
+
+
+
+
+
+
+