（一），什么是文件管理系统
答：数据在PC上是以文件的形式储存在磁盘中的，这些数据的形式一般为ASCII码或二进制形式。简单点说就是：管理磁盘上的文件的方法的代码！
如：我们写到SD卡上面的数据管理一下，更科学的方法来管理
http://elm-chan.org/fsw/ff/00index_e.html，官网介绍 Resources下面是源码
（二），我们在移植时主要是那些函数？
答：Device Control Interface（硬件接口函数）
- disk_status - Get device status 选择操纵的模块，此处用SD卡
- disk_initialize - Initialize device 初始化函数
- disk_read - Read sector(s) 读
- disk_write - Write sector(s) 写
- disk_ioctl - Control device dependent features
- get_fattime - Get current time
（三），例程：
1，我们用的是0.09版本的
2，CC936.c中文字体库
①新建工作区间
/* Register work area for each volume (Always succeeds regardless of disk status) */
f_mount(0,&fs); //（文件管理系统）注册一个工作区间，工作空间命名为0。
那么工作区间的命名范围是什么呢？
答：
FRESULT f_mount (
BYTE vol, /* Logical drive number to be mounted/unmounted */
FATFS *fs /* Pointer to new file system object (NULL for unmount)*/
)
{
FATFS *rfs; if (vol >= _VOLUMES) /* Check if the drive number is valid */
return FR_INVALID_DRIVE;
vol就是f_mount的第一个形参（命名），当他的值大于等于 _VOLUMES，就会返回错误
#define _VOLUMES 1 //can define 9
/* Number of volumes (logical drives) to be used. */
Parameters（官网）
- Drive
- Logical drive number (0-9) to register/unregister the work area.
- FileSystemObject
- Pointer to the work area (file system object) to be registered.
②然后再工作区间里面新建文件
/* function disk_initialize() has been called in f_open */ /* Create new file on the drive 0 */
res = f_open(&fnew, "0:newfile.txt", FA_CREATE_ALWAYS | FA_WRITE );
OPEN的属性：
1.怎么打开呢？
FA_CREATE_ALWAYS 总是以创建总是新建的形式打开这个文件
FA_WRITE：此文件只能写
2.看下open函数
FRESULT f_open (
FIL* FileObject, /* Pointer to the blank file object structure */ 文件指针，把打开的文件关联到这个指针连
const TCHAR* FileName, /* Pointer to the file neme */ 文件名字
BYTE ModeFlags /* Mode flags */ 属性
);
属性：
| Value | Description |
|---|---|
| FA_READ | Specifies read access to the object. Data can be read from the file. Combine with FA_WRITE for read-write access. |
| FA_WRITE | Specifies write access to the object. Data can be written to the file. Combine with FA_READ for read-write access. |
| FA_OPEN_EXISTING | Opens the file. The function fails if the file is not existing. (Default) |
| FA_OPEN_ALWAYS | Opens the file if it is existing. If not, a new file is created. To append data to the file, use f_lseek function after file open in this method. |
| FA_CREATE_NEW | Creates a new file. The function fails with FR_EXIST if the file is existing. |
| FA_CREATE_ALWAYS | Creates a new file. If the file is existing, it is truncated and overwritten. |
可以第一次打开用：FA_CREATE_NEW，之后打开用：FA_OPEN_EXISTING（已存在）就可以了
或者：总是打开，总是关闭
当用到：FA_CREATE_ALWAYS时，我们要将 #define _FS_READONLY 0 /* 0:Read/Write or 1:Read only */ 打开
3.对于返回值（Return Values）：我们只测试：FR_OK（是否成功）
③往该文件内写数据
if ( res == FR_OK )
{
res = f_write(&fnew, textFileBuffer, sizeof(textFileBuffer), &bw);
f_close(&fnew); 写完之后，把该文件关掉
}
④关掉之后再打开它
res = f_open(&fnew, "0:newfile.txt", FA_OPEN_EXISTING | FA_READ); // FA_READ：此时打开定义可读
⑤读取数据
res = f_read(&fnew, buffer, sizeof(buffer), &br);
⑥打印之后关闭
printf("\r\n %s ", buffer);
/* Close open files */
f_close(&fnew);
⑦在文件系统中注册掉刚才开辟的“0”工作区间
/* Unregister work area prior to discard it */
f_mount(0, NULL);
（四）文件管理系统与SD卡的关联！
1，Application：就是我们主函数中使用的那些上层函数
2，中间是文件系统模块，文件系统要操纵底层SD卡的时候呢还需要 Low level disk I/O，这一部分驱动，这一部分驱动需要我们自己写
/*-------------------------- SD Init ----------------------------- */
Status = SD_Init();
if (Status!=SD_OK )
{
return STA_NOINIT;
}
else
{
return RES_OK;
} }
和
/*-----------------------------------------------------------------------*/
/* Return Disk Status */ DSTATUS disk_status (
BYTE drv /* Physical drive nmuber (0..) */
)
{
return RES_OK;
}
底层的磁盘的读/写
/*-----------------------------------------------------------------------*/
/* 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) */
)
{ if (count > 1) //多个磁盘
{
SD_ReadMultiBlocks(buff, sector*BLOCK_SIZE, BLOCK_SIZE, count); /* Check if the Transfer is finished */
SD_WaitReadOperation(); //循环查询dma传输是否结束 /* Wait until end of DMA transfer */
while(SD_GetStatus() != SD_TRANSFER_OK);
}
else //单个磁盘
{ SD_ReadBlock(buff, sector*BLOCK_SIZE, BLOCK_SIZE); /* Check if the Transfer is finished */
SD_WaitReadOperation(); //循环查询dma传输是否结束 /* Wait until end of DMA transfer */
while(SD_GetStatus() != SD_TRANSFER_OK); }
return RES_OK;
} /*-----------------------------------------------------------------------*/
/* 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) */
)
{ if (count > 1)
{
SD_WriteMultiBlocks((uint8_t *)buff, sector*BLOCK_SIZE, BLOCK_SIZE, count); /* Check if the Transfer is finished */
SD_WaitWriteOperation(); //等待dma传输结束
while(SD_GetStatus() != SD_TRANSFER_OK); //等待sdio到sd卡传输结束
}
else
{
SD_WriteBlock((uint8_t *)buff,sector*BLOCK_SIZE, BLOCK_SIZE); /* Check if the Transfer is finished */
SD_WaitWriteOperation(); //等待dma传输结束
while(SD_GetStatus() != SD_TRANSFER_OK); //等待sdio到sd卡传输结束
}
return RES_OK;
}
#endif /* _READONLY */
IO控制为空（直接返回OK）
/*-----------------------------------------------------------------------*/
/* 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;
}
嵌入式初学者，看到此文的大神们，有什么错误的地方多多意见啊！