Posted on March 21, 2018 at 16:42ST's method is to have a 'wedge' DISKIO implementation for FATFS that vectors the block IO calls to the specific storage layer/drive being used. So you have a structure of function pointers, one goes to SDIO/SDMMC, another to USBSTOR/MSC, QSPI, NOR/NAND, etc.
/**
* @brief Gets Disk Status
* @param pdrv: Physical drive number (0..)
* @retval DSTATUS: Operation status
*/
DSTATUS disk_status (
BYTE pdrv /* Physical drive number to identify the drive */
)
{
DSTATUS stat;
stat = disk.drv[pdrv]->disk_status(disk.lun[pdrv]);
return stat;
}
/**
* @brief Initializes a Drive
* @param pdrv: Physical drive number (0..)
* @retval DSTATUS: Operation status
*/
DSTATUS disk_initialize (
BYTE pdrv /* Physical drive nmuber to identify the drive */
)
{
DSTATUS stat = RES_OK;
if(disk.is_initialized[pdrv] == 0)
{
disk.is_initialized[pdrv] = 1;
stat = disk.drv[pdrv]->disk_initialize(disk.lun[pdrv]);
}
return stat;
}
/**
* @brief Reads Sector(s)
* @param pdrv: Physical drive number (0..)
* @param *buff: Data buffer to store read data
* @param sector: Sector address (LBA)
* @param count: Number of sectors to read (1..128)
* @retval DRESULT: Operation result
*/
DRESULT disk_read (
BYTE pdrv, /* Physical drive nmuber to identify the drive */
BYTE *buff, /* Data buffer to store read data */
DWORD sector, /* Sector address in LBA */
UINT count /* Number of sectors to read */
)
{
DRESULT res;
res = disk.drv[pdrv]->disk_read(disk.lun[pdrv], buff, sector, count);
return res;
}
The MSC implementation has to provide a number of SCSI/ATAPI-MMC type commands (READ, WRITE, TEST-UNIT-READY, GET CAPACITY, INQUIRY, etc), as your Windows/Linux system sends IO requests to the media, and implements the FAT, NTFS, UDF etc with File System drivers on the host, NOT on the flash stick or external hard drive.
