FATFS
(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!
郑重声明:本站内容如果来自互联网及其他传播媒体,其版权均属原媒体及文章作者所有。转载目的在于传递更多信息及用于网络分享,并不代表本站赞同其观点和对其真实性负责,也不构成任何其他建议。