STM32 Note SD card reading and writing and FatFS file system

Because I need to use it, I learned how to operate the SD card with SPI, and at the same time transplanted a free and open source FAT file system: FatFS. It feels good. I have realized the operation of reading and writing files on the microcontroller. Next, I can explain my G code!
　　My SD card underlying operation refers to several common codes on the Internet, but I have also made some optimizations to its structure, at least it looks more convenient to use. It can be used as the diskio of the file system, or you can directly use the underlying function to read and write the SD card as a flash.
　　The FatFs file system is quite small, 6-7K is enough, which is very suitable for the STM32 with 128K flash, and the cost is not high. At the same time, it is highly portable, and at least only 4 functions need to be modified to realize the transplantation of the file system. For an introduction to the relevant file system, please see here .
　　Here is a relatively complete set of reference materials, including the original materials of the fatfs file system, several important manuals and codes downloaded from the Internet.
http://www.ouravr.com/bbs/bbs_content.jsp?bbs_sn=3210864&bbs_page_no=1&bbs_id=3020

　　Below is my code:

　　The underlying SPI bus operation on the SD card is in SPI_SD_driver.c/h, and the disk operation function in the FATFS transplant file diskio.c will call the underlying operation function. Here are some low-level operation functions:
u8 SPI_ReadWriteByte(u8 TxData); //SPI bus reads and writes a byte
u8 SD_WaitReady(void); //Wait for SD card to be ready
u8 SD_SendCommand(u8 cmd, u32 arg, u8 crc); //SD card sends a command
u8 SD_SendCommand_NoDeassert(u8 cmd, u32 arg, u8 crc); //SD card sends a command, no disconnection
u8 SD_Init(void); //SD card initialization
                                  
u8 SD_ReceiveData(u8 *data, u16 len, u8 release); //SD card read data
u8 SD_GetCID(u8 *cid_data); //Read SD card CID
u8 SD_GetCSD(u8 *csd_data); //Read SD card CSD
u32 SD_GetCapacity(void); //Get SD card capacity

u8 SD_ReadSingleBlock(u32 sector, u8 *buffer); //Read a sector
u8 SD_WriteSingleBlock(u32 sector, const u8 *buffer); //Write a sector
u8 SD_ReadMultiBlock(u32 sector, u8 *buffer, u8 count); //Read multiple sectors
u8 SD_WriteMultiBlock(u32 sector, const u8 *data, u8 count); //Write multiple sectors

　　This is a piece of code in diskio.c. In the disk initialization, we called the SD card initialization function in SPI_SD_driver.c.
DSTATUS disk_initialize (
    BYTE drv /* Physical drive nmuber (0..) */
)
{
    u8 state;

    if(drv)
    {
        return STA_NOINIT; //Only supports operations on disk 0
    }

    state = SD_Init();
    if(state == STA_NODISK)
    {
        return STA_NODISK;
    }
    else if(state != 0)
    {
        return STA_NOINIT; //Other errors: initialization failed
    }
    else
    {
        return 0; //Initialization successful
    }
}
　　
　 　In short, the FATFS file system has high portability. After testing, under the 18MSPI clock of STM32, the file reading speed is more than 300K per second, and the file writing speed is also more than 100K. It should be said that it basically meets the speed requirements for disk reading and writing in embedded engineering applications. If the SD card reading and writing code is further optimized, the speed should be improved to a certain extent. At the same time, it should be noted that the reading and writing speed of FLASH itself is not as fast as RAM. By replacing the SD card, it is found that the reading and writing speed is directly related to the card itself, so you should try to choose a faster card.