创建媒体驱动程序：写入扇区
[创建 FreeRTOS-Plus-FAT 媒体驱动程序]

每个 FreeRTOS-Plus-FAT 媒体驱动程序都需要一个函数来将扇区写入存储嵌入式文件系统的媒体。写入函数的实际作用取决于媒体类型。例如，如果媒体是 RAM 磁盘，则可以使用 memcpy() 将数据写入 RAM，但如果媒体是 SD 卡，则卡的命令接口将必须通过 MMC 或 SPI 外围设备驱动器使用。

写入函数

写入函数可以使用任何名称，但必须具备以下原型：



int32_t FFWrite( uint8_t *pucSource,      /* Source of data to be written. */

                 uint32_t ulSectorNumber, /* The first sector being written to. */

                 uint32_t ulSectorCount,  /* The number of sectors to write. */

                 FF_Disk_t *pxDisk );     /* Describes the disk being written to. */



The prototype of a function used to write to the media that holds the embedded file system

以下示例大致描述了 FreeRTOS-Plus-FAT RAM 磁盘驱动器中使用的读取函数。完整版本包含输入参数检查，， /FreeRTOS-Plus/Source/FreeRTOS-Plus-FAT/portable/common/ff_ramdisk.c。



/* Each sector is 512 bytes. */

#define ramSECTOR_SIZE    512



static int32_t prvWriteRAM( uint8_t *pucSource,

                            uint32_t ulSectorNumber,

                            uint32_t ulSectorCount,

                            FF_Disk_t *pxDisk )

{

uint8_t *pucDestination;



    /* The FF_Disk_t structure describes the media being accessed.  Attributes that

    are common to all media types are stored in the structure directly.  The pvTag

    member of the structure is used to add attributes that are specific to the media

    actually being accessed.  In the case of the RAM disk the pvTag member is just

    used to point to the RAM buffer being used as the disk. */

    pucDestination = ( uint8_t * ) pxDisk->pvTag;



    /* Move to the start of the sector being written. */

    pucDestination += ( ramSECTOR_SIZE * ulSectorNumber );



    /* Copy the data to the disk.  As this is a RAM disk data can be copied

    using memcpy(). */

    memcpy( ( void * ) pucDestination,

            ( void * ) pucSource,

            ( size_t ) ( ulSectorCount * ramSECTOR_SIZE ) );



    return FF_ERR_NONE;

}



The write function used by the RAM disk driver - for clarity input parameter checking is not shown

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创建媒体驱动程序： 写入扇区 [创建 FreeRTOS-Plus-FAT 媒体驱动程序]

写入函数

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创建媒体驱动程序：写入扇区
[创建 FreeRTOS-Plus-FAT 媒体驱动程序]