It is a block storage device so will act like a hard drive or NAND, not like SRAM.
You don't need to use FATFS, but you will need to read/write block(s). Review the DISKIO.C for the FATFS implementations to see how that happens.
For SPI the best example to start with might be the ADAFRUIT one.
Interfaces via read/write block functions
STM32Cube_FW_F2_V1.7.0\Drivers\BSP\Adafruit_Shield\stm32_adafruit_sd.c
/**
* @brief Reads block(s) from a specified address in the SD card, in polling mode.
* @param pData: Pointer to the buffer that will contain the data to transmit
* @param ReadAddr: Address from where data is to be read. The address is counted
* in blocks of 512bytes
* @param NumOfBlocks: Number of SD blocks to read
* @param Timeout: This parameter is used for compatibility with BSP implementation
* @retval SD status
*/
uint8_t BSP_SD_ReadBlocks(uint32_t *pData, uint32_t ReadAddr, uint32_t NumOfBlocks, uint32_t Timeout)
STM32Cube_FW_F2_V1.7.0\Middlewares\Third_Party\FatFs\src\drivers\sd_diskio.c
/**
* @brief Reads Sector(s)
* @param lun : not used
* @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 SD_read(BYTE lun, BYTE *buff, DWORD sector, UINT count)
{
DRESULT res = RES_ERROR;
uint32_t timeout = 100000;
if(BSP_SD_ReadBlocks((uint32_t*)buff,
(uint32_t) (sector),
count, SD_DATATIMEOUT) == MSD_OK)
{
while(BSP_SD_GetCardState()!= MSD_OK)
{
if (timeout-- == 0)
{
return RES_ERROR;
}
}
res = RES_OK;
}
return res;
}
