什么是文件系统
负责管理和存储文件信息的软件机构，在磁盘上组织文件的方法。
常用的文件系统
FAT/FATFS 小型嵌入式系统
NTFS WINDOWS
CDFS 光盘
exFAT 更适用于闪存
FATFS优点
：免费开源，专门为小型嵌入式系统设计，c编写，支持FAT12, FAT16 与 FAT32，支持多种存储媒介,有独立的缓冲区，可对多个文件进行读写，可裁剪的文件系统（极为重要）
FATFS的特点：
由于它以上的特点，使得FATFS在嵌入式系统中被广泛的使用
①底层接口，包括存储媒介读／写接口（disk I/O）和供给文件创建修改时间的实时时钟，需要我们根据平台和存储介质编写移植代码。
②中间层FATFS模块，实现了FAT 文件读／写协议。FATFS模块提供的是ff.c和ff.h。除非有必要，使用者一般不用修改，使用时将头文件直接包含进去即可。
③最顶层是应用层，使用者无需理会FATFS的内部结构和复杂的FAT 协议，只需要调用FATFS模块提供给用户的一系列应用接口函数，如f_open，f_read，f_write 和f_close等，就可以像在PC 上读／写文件那样简单。
FATFS的整个系统包可以在FATFS的官网下载：官网地址
同时在官网还可以查看每个函数的说明，同时大部分的函数都带有示例，是不错的学习资源。
fatfs文件系统
diskio.c和diskio.h是硬件层，需要根据存储介质来修改
ff.c和ff.h是FATFS的文件系统层和文件系统的API层
移植步骤
： 1、数据类型：在integer.h 里面去定义好数据的类型。这里需要了解你用的编
译器的数据类型，并根据编译器定义好数据类型。
2、配置：通过ffconf.h配置FATFS的相关功能，以满足你的需要。
3、函数编写：打开diskio.c，进行底层驱动编写，一般需要编写6 个接口函数
相关配置宏：
_FS_TINY mini版本的FATFS
_FS_READONLY 设置只读，可以减少所占的空间
_FS_MINIMIZE 削减函数
_USE_STRFUNC 字符及字符串操作函数
_USE_MKFS 是否启用格式化
_USE_FASTSEEK 使能快速定位
_USE_LABEL 是否支持磁盘盘符的设置和读取
_CODE_PAGE 设置语言936-中文GBK编码
_USE_LFN 是否支持长文件名，值不同存储的位置不同
_MAX_LFN 文件名的最大长度
_VOLUMES 支持的逻辑设备数目
_MAX_SS 扇区缓冲最大值，一般为512
STM32F407开发板diskio.c配置
/*-----------------------------------------------------------------------*/
/* Low level disk I/O module skeleton for FatFs (C)ChaN, 2013 */
/*-----------------------------------------------------------------------*/
/* 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 "sdio_sdcard.h"
#include "w25qxx.h"
#include "malloc.h"
#define SD_CARD 0 //SD卡,卷标为0
#define EX_FLASH 1 //外部flash,卷标为1
#define FLASH_SECTOR_SIZE 512
//对于W25Q128
//前12M字节给fatfs用,12M字节后,用于存放字库,字库占用3.09M. 剩余部分,给客户自己用
u16 FLASH_SECTOR_COUNT=2048*12; //W25Q1218,前12M字节给FATFS占用
#define FLASH_BLOCK_SIZE 8 //每个BLOCK有8个扇区
//初始化磁盘
DSTATUS disk_initialize (
BYTE pdrv /* Physical drive nmuber (0..) */
)
{
u8 res=0;
switch(pdrv)
{
case SD_CARD://SD卡
res=SD_Init();//SD卡初始化
break;
case EX_FLASH://外部flash
W25QXX_Init();
FLASH_SECTOR_COUNT=2048*12;//W25Q1218,前12M字节给FATFS占用
break;
default:
res=1;
}
if(res)return STA_NOINIT;
else return 0; //初始化成功
}
//获得磁盘状态
DSTATUS disk_status (
BYTE pdrv /* Physical drive nmuber (0..) */
)
{
return 0;
}
//读扇区
//drv:磁盘编号0~9
//*buff:数据接收缓冲首地址
//sector:扇区地址
//count:需要读取的扇区数
DRESULT disk_read (
BYTE pdrv, /* Physical drive nmuber (0..) */
BYTE *buff, /* Data buffer to store read data */
DWORD sector, /* Sector address (LBA) */
UINT count /* Number of sectors to read (1..128) */
)
{
u8 res=0;
if (!count)return RES_PARERR;//count不能等于0，否则返回参数错误
switch(pdrv)
{
case SD_CARD://SD卡
res=SD_ReadDisk(buff,sector,count);
while(res)//读出错
{
SD_Init(); //重新初始化SD卡
res=SD_ReadDisk(buff,sector,count);
//printf("sd rd error:%d\r\n",res);
}
break;
case EX_FLASH://外部flash
for(;count>0;count--)
{
W25QXX_Read(buff,sector*FLASH_SECTOR_SIZE,FLASH_SECTOR_SIZE);
sector++;
buff+=FLASH_SECTOR_SIZE;
}
res=0;
break;
default:
res=1;
}
//处理返回值，将SPI_SD_driver.c的返回值转成ff.c的返回值
if(res==0x00)return RES_OK;
else return RES_ERROR;
}
//写扇区
//drv:磁盘编号0~9
//*buff:发送数据首地址
//sector:扇区地址
//count:需要写入的扇区数
#if _USE_WRITE
DRESULT disk_write (
BYTE pdrv, /* Physical drive nmuber (0..) */
const BYTE *buff, /* Data to be written */
DWORD sector, /* Sector address (LBA) */
UINT count /* Number of sectors to write (1..128) */
)
{
u8 res=0;
if (!count)return RES_PARERR;//count不能等于0，否则返回参数错误
switch(pdrv)
{
case SD_CARD://SD卡
res=SD_WriteDisk((u8*)buff,sector,count);
while(res)//写出错
{
SD_Init(); //重新初始化SD卡
res=SD_WriteDisk((u8*)buff,sector,count);
//printf("sd wr error:%d\r\n",res);
}
break;
case EX_FLASH://外部flash
for(;count>0;count--)
{
W25QXX_Write((u8*)buff,sector*FLASH_SECTOR_SIZE,FLASH_SECTOR_SIZE);
sector++;
buff+=FLASH_SECTOR_SIZE;
}
res=0;
break;
default:
res=1;
}
//处理返回值，将SPI_SD_driver.c的返回值转成ff.c的返回值
if(res == 0x00)return RES_OK;
else return RES_ERROR;
}
#endif
//其他表参数的获得
//drv:磁盘编号0~9
//ctrl:控制代码
//*buff:发送/接收缓冲区指针
#if _USE_IOCTL
DRESULT disk_ioctl (
BYTE pdrv, /* Physical drive nmuber (0..) */
BYTE cmd, /* Control code */
void *buff /* Buffer to send/receive control data */
)
{
DRESULT res;
if(pdrv==SD_CARD)//SD卡
{
switch(cmd)
{
case CTRL_SYNC:
res = RES_OK;
break;
case GET_SECTOR_SIZE:
*(DWORD*)buff = 512;
res = RES_OK;
break;
case GET_BLOCK_SIZE:
*(WORD*)buff = SDCardInfo.CardBlockSize;
res = RES_OK;
break;
case GET_SECTOR_COUNT:
*(DWORD*)buff = SDCardInfo.CardCapacity/512;
res = RES_OK;
break;
default:
res = RES_PARERR;
break;
}
}else if(pdrv==EX_FLASH) //外部FLASH
{
switch(cmd)
{
case CTRL_SYNC:
res = RES_OK;
break;
case GET_SECTOR_SIZE:
*(WORD*)buff = FLASH_SECTOR_SIZE;
res = RES_OK;
break;
case GET_BLOCK_SIZE:
*(WORD*)buff = FLASH_BLOCK_SIZE;
res = RES_OK;
break;
case GET_SECTOR_COUNT:
*(DWORD*)buff = FLASH_SECTOR_COUNT;
res = RES_OK;
break;
default:
res = RES_PARERR;
break;
}
}else res=RES_ERROR;//其他的不支持
return res;
}
#endif
//获得时间
//User defined function to give a current time to fatfs module */
//31-25: Year(0-127 org.1980), 24-21: Month(1-12), 20-16: Day(1-31) */
//15-11: Hour(0-23), 10-5: Minute(0-59), 4-0: Second(0-29 *2) */
DWORD get_fattime (void)
{
return 0;
}
//动态分配内存
void *ff_memalloc (UINT size)
{
return (void*)mymalloc(SRAMIN,size);
}
//释放内存
void ff_memfree (void* mf)
{
myfree(SRAMIN,mf);
}
ffconf.h配置
/*---------------------------------------------------------------------------/
/ FatFs - FAT file system module configuration file R0.10b (C)ChaN, 2014
/---------------------------------------------------------------------------*/
#ifndef _FFCONF
#define _FFCONF 8051 /* Revision ID */
/*---------------------------------------------------------------------------/
/ Functions and Buffer Configurations
/---------------------------------------------------------------------------*/
#define _FS_TINY 0 /* 0:Normal or 1:Tiny */
/* When _FS_TINY is set to 1, it reduces memory consumption _MAX_SS bytes each
/ file object. For file data transfer, FatFs uses the common sector buffer in
/ the file system object (FATFS) instead of private sector buffer eliminated
/ from the file object (FIL). */
#define _FS_READONLY 0 /* 0:Read/Write or 1:Read only */
/* Setting _FS_READONLY to 1 defines read only configuration. This removes
/ writing functions, f_write(), f_sync(), f_unlink(), f_mkdir(), f_chmod(),
/ f_rename(), f_truncate() and useless f_getfree(). */
#define _FS_MINIMIZE 0 /* 0 to 3 */
/* The _FS_MINIMIZE option defines minimization level to remove API functions.
/
/ 0: All basic functions are enabled.
/ 1: f_stat(), f_getfree(), f_unlink(), f_mkdir(), f_chmod(), f_utime(),
/ f_truncate() and f_rename() function are removed.
/ 2: f_opendir(), f_readdir() and f_closedir() are removed in addition to 1.
/ 3: f_lseek() function is removed in addition to 2. */
#define _USE_STRFUNC 1 /* 0:Disable or 1-2:Enable */
/* To enable string functions, set _USE_STRFUNC to 1 or 2. */
#define _USE_MKFS 1 /* 0:Disable or 1:Enable */
/* To enable f_mkfs() function, set _USE_MKFS to 1 and set _FS_READONLY to 0 */
#define _USE_FASTSEEK 1 /* 0:Disable or 1:Enable */
/* To enable fast seek feature, set _USE_FASTSEEK to 1. */
#define _USE_LABEL 1 /* 0:Disable or 1:Enable */
/* To enable volume label functions, set _USE_LAVEL to 1 */
#define _USE_FORWARD 0 /* 0:Disable or 1:Enable */
/* To enable f_forward() function, set _USE_FORWARD to 1 and set _FS_TINY to 1. */
/*---------------------------------------------------------------------------/
/ Locale and Namespace Configurations
/---------------------------------------------------------------------------*/
#define _CODE_PAGE 936 //采用中文GBK编码
/* 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 (Valid for only non-LFN configuration) */
#define _USE_LFN 3 /* 0 to 3 */
#define _MAX_LFN 255 /* Maximum LFN length to handle (12 to 255) */
/* The _USE_LFN option switches the LFN feature.
/
/ 0: Disable LFN feature. _MAX_LFN has no effect.
/ 1: Enable LFN with static working buffer on the BSS. Always NOT thread-safe.
/ 2: Enable LFN with dynamic working buffer on the STACK.
/ 3: Enable LFN with dynamic working buffer on the HEAP.
/
/ When enable LFN feature, Unicode handling functions ff_convert() and ff_wtoupper()
/ function must be added to the project.
/ The LFN working buffer occupies (_MAX_LFN + 1) * 2 bytes. When use stack for the
/ working buffer, take care on stack overflow. When use heap memory for the working
/ buffer, memory management functions, ff_memalloc() and ff_memfree(), must be added
/ to the project. */
#define _LFN_UNICODE 0 /* 0:ANSI/OEM or 1:Unicode */
/* To switch the character encoding on the FatFs API (TCHAR) to Unicode, enable LFN
/ feature and set _LFN_UNICODE to 1. This option affects behavior of string I/O
/ functions. This option must be 0 when LFN feature is not enabled. */
#define _STRF_ENCODE 3 /* 0:ANSI/OEM, 1:UTF-16LE, 2:UTF-16BE, 3:UTF-8 */
/* When Unicode API is enabled by _LFN_UNICODE option, this option selects the character
/ encoding on the file to be read/written via string I/O functions, f_gets(), f_putc(),
/ f_puts and f_printf(). This option has no effect when _LFN_UNICODE == 0. Note that
/ FatFs supports only BMP. */
#define _FS_RPATH 0 /* 0 to 2 */
/* The _FS_RPATH option configures relative path feature.
/
/ 0: Disable relative path feature and remove related functions.
/ 1: Enable relative path. f_chdrive() and f_chdir() function are available.
/ 2: f_getcwd() function is available in addition to 1.
/
/ Note that output of the f_readdir() fnction is affected by this option. */
/*---------------------------------------------------------------------------/
/ Drive/Volume Configurations
/---------------------------------------------------------------------------*/
#define _VOLUMES 3 //支持3个磁盘
/* Number of volumes (logical drives) to be used. */
#define _STR_VOLUME_ID 0 /* 0:Use only 0-9 for drive ID, 1:Use strings for drive ID */
#define _VOLUME_STRS "RAM","NAND","CF","SD1","SD2","USB1","USB2","USB3"
/* When _STR_VOLUME_ID is set to 1, also pre-defined strings can be used as drive
/ number in the path name. _VOLUME_STRS defines the drive ID strings for each logical
/ drives. Number of items must be equal to _VOLUMES. Valid characters for the drive ID
/ strings are: 0-9 and A-Z. */
#define _MULTI_PARTITION 0 /* 0:Single partition, 1:Enable multiple partition */
/* By default(0), each logical drive number is bound to the same physical drive number
/ and only a FAT volume found on the physical drive is mounted. When it is set to 1,
/ each logical drive number is bound to arbitrary drive/partition listed in VolToPart[].
*/
#define _MIN_SS 512
#define _MAX_SS 512
/* These options configure the range of sector size to be supported. (512, 1024, 2048 or
/ 4096) Always set both 512 for most systems, all memory card and harddisk. But a larger
/ value may be required for on-board flash memory and some type of optical media.
/ When _MAX_SS is larger than _MIN_SS, FatFs is configured to variable sector size and
/ GET_SECTOR_SIZE command must be implemented to the disk_ioctl() function. */
#define _USE_ERASE 0 /* 0:Disable or 1:Enable */
/* To enable sector erase feature, set _USE_ERASE to 1. Also CTRL_ERASE_SECTOR command
/ should be added to the disk_ioctl() function. */
#define _FS_NOFSINFO 0 /* 0 to 3 */
/* If you need to know correct free space on the FAT32 volume, set bit 0 of this option
/ and f_getfree() function at first time after volume mount will force a full FAT scan.
/ Bit 1 controls the last allocated cluster number as bit 0.
/
/ bit0=0: Use free cluster count in the FSINFO if available.
/ bit0=1: Do not trust free cluster count in the FSINFO.
/ bit1=0: Use last allocated cluster number in the FSINFO if available.
/ bit1=1: Do not trust last allocated cluster number in the FSINFO.
*/
/*---------------------------------------------------------------------------/
/ System Configurations
/---------------------------------------------------------------------------*/
#define _FS_LOCK 0 /* 0:Disable or >=1:Enable */
/* To enable file lock control feature, set _FS_LOCK to non-zero value.
/ The value defines how many files/sub-directories can be opened simultaneously
/ with file lock control. This feature uses bss _FS_LOCK * 12 bytes. */
#define _FS_REENTRANT 0 /* 0:Disable or 1:Enable */
#define _FS_TIMEOUT 1000 /* Timeout period in unit of time tick */
#define _SYNC_t HANDLE /* O/S dependent sync object type. e.g. HANDLE, OS_EVENT*, ID, SemaphoreHandle_t and etc.. */
/* The _FS_REENTRANT option switches the re-entrancy (thread safe) of the FatFs module.
/
/ 0: Disable re-entrancy. _FS_TIMEOUT and _SYNC_t have no effect.
/ 1: Enable re-entrancy. Also user provided synchronization handlers,
/ ff_req_grant(), ff_rel_grant(), ff_del_syncobj() and ff_cre_syncobj()
/ function must be added to the project.
*/
#define _WORD_ACCESS 0 /* 0 or 1 */
/* The _WORD_ACCESS option is an only platform dependent option. It defines
/ which access method is used to the word data on the FAT volume.
/
/ 0: Byte-by-byte access. Always compatible with all platforms.
/ 1: Word access. Do not choose this unless under both the following conditions.
/
/ * Address misaligned memory access is always allowed for ALL instructions.
/ * Byte order on the memory is little-endian.
/
/ If it is the case, _WORD_ACCESS can also be set to 1 to improve performance and
/ reduce code size. Following table shows an example of some processor types.
/
/ ARM7TDMI 0 ColdFire 0 V850E 0
/ Cortex-M3 0 Z80 0/1 V850ES 0/1
/ Cortex-M0 0 RX600(LE) 0/1 TLCS-870 0/1
/ AVR 0/1 RX600(BE) 0 TLCS-900 0/1
/ AVR32 0 RL78 0 R32C 0
/ PIC18 0/1 SH-2 0 M16C 0/1
/ PIC24 0 H8S 0 MSP430 0
/ PIC32 0 H8/300H 0 x86 0/1
*/
#endif /* _FFCONF */
可以看出我使用了Normal FATFS、可以读写、保留了全部函数、使能了字符串操作、使能了格式化操作、使能了快速定位、支持磁盘盘符的设置和读取、设置语言936-中文GBK编码、支持长文件名且最大长度255、支持的逻辑设备数目为3、扇区缓冲最大值最小值都为512 FATFS给用户提供了大量的API函数，可以满足我们对文件的各种操作。
FATFS给用户提供了大量的API函数，可以满足我们对文件的各种操作。
在官网有详细的使用指南，看着使用指南再对照源码就会基本掌握函数的使用。
几个重要结构体：
文件对象结构体（FIL类型）：存放文件的相关信息，打开关闭读写文件等操作时需要使用其指针
目录对象结构体（DIR类型）：存放目录的相关信息，对目录操作时需要其指针
文件状态结构体（FILINFO类型）：存放文件的大小属性文件名等信息
文件系统对象结构体（FATFS类型）：暂时没见怎么用过
文件的属性宏定义（用在打开时）： 可以使用或运算符使得该文件具有多种性质，注意在读写时一定要以相应的属性打开文件
文件夹文件属性宏定义：可以使用或运算符使得该文件具有多种性质，提供了函数可以修改文件的属性
注意：传参时的path(路径)应为一个字符串，是要操作的文件的完整路径，根目录0表示SD 卡，1表示外部SRAM
要注意数据类型的统一，在integer.h中定义的文件系统所用到的数据类型
大部分函数若执行成功返回0，若失败会返回一个错误码，该错误码为枚举类型（FRESULT）中的成员，在调试时打印错误码会事半功倍