SD卡fat文件系统移植

经过充分的研究，发现fatfs文件系统移植的比较简单！因为代码都已经被别人做好了！我们只需把io层稍稍做个处理就ok了；

至于sd卡的驱动请看我这篇博客：http://blog.csdn.net/ieczw/article/details/17378475

移植是以这个驱动为前提的！！

http://elm-chan.org/fsw/ff/00index_e.html

这个网站发布了所有版本的文件fatfs文件系统，我这次下载最新版的http://elm-chan.org/fsw/ff/ff9a.zip

直接解压，里面有两个文件，一个是src，另一个是doc；

把src放到自己的工程目录下面，并添加。首先看看00Readme.txt，我们主要是关注这些东西

FILES

  ffconf.h   Configuration file for FatFs module.
  ff.h       Common include file for FatFs and application module.
  ff.c       FatFs module.
  diskio.h   Common include file for FatFs and disk I/O module.
  diskio.c   An example of glue function to attach existing disk I/O module to FatFs.
  integer.h  Integer type definitions for FatFs.
  option     Optional external functions.

  Low level disk I/O module is not included in this archive because the FatFs
  module is only a generic file system layer and not depend on any specific
  storage device. You have to provide a low level disk I/O module that written
  to control your storage device.

所以我们主要修改的是diskio.c

DSTATUS disk_initialize (BYTE pdrv);
DSTATUS disk_status (BYTE pdrv);
DRESULT disk_read (BYTE pdrv, BYTE*buff, DWORD sector, BYTE count);
DRESULT disk_write (BYTE pdrv, const BYTE* buff, DWORD sector, BYTE count);
DRESULT disk_ioctl (BYTE pdrv, BYTE cmd, void* buff);

我们需要改的是这几个底层io函数，按照下面的修改，我想大家应该能懂！

/*-----------------------------------------------------------------------*/
/* Low level disk I/O module skeleton for FatFs     (C)ChaN, 2012        */
/*-----------------------------------------------------------------------*/
/* If a working storage control module is available, it should be        */
/* attached to the FatFs via a glue function rather than modifying it.   */
/* This is an example of glue functions to attach various exsisting      */
/* storage control module to the FatFs module with a defined API.        */
/*-----------------------------------------------------------------------*/

#include "diskio.h"		/* FatFs lower layer API */
#include "stm32_eval_sdio_sd.h"

/* Definitions of physical drive number for each media */
#define ATA		0
#define MMC		1
#define USB		2

#define SECTOR_SIZE 512U

/*-----------------------------------------------------------------------*/
/* Inidialize a Drive                                                    */

DSTATUS disk_initialize (
	BYTE drv				/* Physical drive nmuber (0..) */
)
{
	return SD_Init();
}

/*-----------------------------------------------------------------------*/
/* Return Disk Status                                                    */

DSTATUS disk_status (
	BYTE drv		/* Physical drive nmuber (0..) */
)
{
	return SD_GetStatus();
}

/*-----------------------------------------------------------------------*/
/* Read Sector(s)                                                        */

DRESULT disk_read (
	BYTE drv,		/* Physical drive nmuber (0..) */
	BYTE *buff,		/* Data buffer to store read data */
	DWORD sector,	/* Sector address (LBA) */
	BYTE count		/* Number of sectors to read (1..255) */
)
{
	return (DRESULT)SD_ReadBlock(buff,sector << 9 ,count);
}

/*-----------------------------------------------------------------------*/
/* Write Sector(s)                                                       */

#if _READONLY == 0
DRESULT disk_write (
	BYTE drv,			/* Physical drive nmuber (0..) */
	const BYTE *buff,	/* Data to be written */
	DWORD sector,		/* Sector address (LBA) */
	BYTE count			/* Number of sectors to write (1..255) */
)
{
	return (DRESULT)SD_WriteBlock((uint8_t *)buff,sector << 9 ,count);
}
#endif /* _READONLY */

/*-----------------------------------------------------------------------*/
/* Miscellaneous Functions                                               */

DRESULT disk_ioctl (
	BYTE drv,		/* Physical drive nmuber (0..) */
	BYTE ctrl,		/* Control code */
	void *buff		/* Buffer to send/receive control data */
)
{
	return RES_OK;
}

unsigned short get_fattime(void){
	return 0;
}

这些修改完后，如果你直接编译会出现如下错误：

..\fatfs\cc936.c(11): error:  #35: #error directive: This file is not needed in current configuration. Remove from the project.

找到cc936.c，他的头文件是这样定义的

/*------------------------------------------------------------------------*/
/* Unicode - OEM code bidirectional converter  (C)ChaN, 2009              */
/*                                                                        */
/* CP936 (Simplified Chinese GBK)                                         */
/*------------------------------------------------------------------------*/

#include "../ff.h"

#if !_USE_LFN || _CODE_PAGE != 936
#error This file is not needed in current configuration. Remove from the project.
#endif

他是找不到USE_LFN或者_CODE_PAGE !=936

那么可能头文件处理问题，大家应该发现问题了，把头文件修改下：#include "ff.h"

为什么要用936的呢？大家看ffconf.h，有这么一段注释

/*---------------------------------------------------------------------------/
/ Locale and Namespace Configurations
/----------------------------------------------------------------------------*/

#define _CODE_PAGE	936
/* The _CODE_PAGE specifies the OEM code page to be used on the target system.
/  Incorrect setting of the code page can cause a file open failure.
/
/   932  - Japanese Shift-JIS (DBCS, OEM, Windows)
/   936  - Simplified Chinese GBK (DBCS, OEM, Windows)
/   949  - Korean (DBCS, OEM, Windows)
/   950  - Traditional Chinese Big5 (DBCS, OEM, Windows)
/   1250 - Central Europe (Windows)
/   1251 - Cyrillic (Windows)
/   1252 - Latin 1 (Windows)
/   1253 - Greek (Windows)
/   1254 - Turkish (Windows)
/   1255 - Hebrew (Windows)
/   1256 - Arabic (Windows)
/   1257 - Baltic (Windows)
/   1258 - Vietnam (OEM, Windows)
/   437  - U.S. (OEM)
/   720  - Arabic (OEM)
/   737  - Greek (OEM)
/   775  - Baltic (OEM)
/   850  - Multilingual Latin 1 (OEM)
/   858  - Multilingual Latin 1 + Euro (OEM)
/   852  - Latin 2 (OEM)
/   855  - Cyrillic (OEM)
/   866  - Russian (OEM)
/   857  - Turkish (OEM)
/   862  - Hebrew (OEM)
/   874  - Thai (OEM, Windows)
/	1    - ASCII only (Valid for non LFN cfg.)
*/

所以，因为我们是中国人，所以我们要用936！哈哈。。。

然后编译又出现另一个问题：

..\output\stm32.axf: Error: L6218E: Undefined symbol get_fattime (referred from ff.o).

这个我们需要自己添加，我在上面修改diskio.c的时候已经添加了。

这些做完之后，也算移植玩了，简单吧，至于如何使用，我们还是看下载网页：http://elm-chan.org/fsw/ff/00index_e.html

或者双击doc/目录下的00index_e.html

Application Interface

FatFs module provides following functions to the applications. In other words, this list describes what FatFs can do to access the FAT volumes.
f_open - Open/Create a file
f_close - Close an open file
f_read - Read file
f_write - Write file
f_lseek - Move read/write pointer, Expand file size
f_truncate - Truncate file size
f_sync - Flush cached data
f_forward - Forward file data to the stream
f_stat - Check existance of a file or sub-directory
f_opendir - Open a directory
f_closedir - Close an open directory
f_readdir - Read a directory item
f_mkdir - Create a sub-directory
f_unlink - Remove a file or sub-directory
f_chmod - Change attribute
f_utime - Change timestamp
f_rename - Rename/Move a file or sub-directory
f_chdir - Change current directory
f_chdrive - Change current drive
f_getcwd - Retrieve the current directory
f_getfree - Get free clusters
f_getlabel - Get volume label
f_setlabel - Set volume label
f_mount - Register/Unregister a work area
f_mkfs - Create a file system on the drive
f_fdisk - Divide a physical drive
f_gets - Read a string
f_putc - Write a character
f_puts - Write a string
f_printf - Write a formatted string
f_tell - Get current read/write pointer
f_eof - Test for end-of-file on a file
f_size - Get size of a file
f_error - Test for an error on a file

里面对每个函数都做了说明，这样就有点像linux操作系统里面的文件io操作了。

我们可以任意点击去一个函数，里面都有例程，我们可以用这些例程来测试下

/* 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;
}

好，基于STM32的fatfs文件系统移植就到这里了！！！！

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