1.SDIO配置
SDIO的引脚不像UART和SPI等数字外设一样可以灵巧配置，它是固定的几个引脚，如下图
利用起来也比较大略，干系的库函数已经封装好了，直接调用就行。
首先须要配置一下干系引脚的复用功能为SDIO：
PORT_Init(PORTB, PIN1, PORTB_PIN1_SD_CLK, 0); PORT_Init(PORTB, PIN2, PORTB_PIN2_SD_CMD, 1); PORT_Init(PORTB, PIN3, PORTB_PIN3_SD_D0, 1); PORT_Init(PORTB, PIN4, PORTB_PIN4_SD_D1, 1); PORT_Init(PORTB, PIN5, PORTB_PIN5_SD_D2, 1); PORT_Init(PORTB, PIN6, PORTB_PIN6_SD_D3, 1);
然后直接调用初始化的函数就行：
result = SDIO_Init(10000000);
个中形参为SDIO的时钟频率。
SD卡读写的干系函数也已经封装好了，包括DMA和非DMA办法，直接调用即可：
uint32_t SDIO_BlockWrite(uint32_t block_addr, uint32_t buff[]);uint32_t SDIO_BlockRead(uint32_t block_addr, uint32_t buff[]);uint32_t SDIO_MultiBlockWrite(uint32_t block_addr, uint16_t block_cnt, uint32_t buff[]);uint32_t SDIO_MultiBlockRead(uint32_t block_addr, uint16_t block_cnt, uint32_t buff[]);uint32_t SDIO_DMABlockWrite(uint32_t block_addr, uint16_t block_cnt, uint32_t buff[]);uint32_t SDIO_DMABlockRead(uint32_t block_addr, uint16_t block_cnt, uint32_t buff[]);
2.FatFs移植
底层读写函数有了往后，移植FatFs也就比较大略了，首先将FatFs的干系文件添加到工程中：
我们须要实现的接口函数在diskio.c文件中，包括至少以下3个函数：
初始化函数，直接将端口配置、SDIO初始化添加到该函数中：
DSTATUS disk_initialize ( BYTE pdrv / Physical drive nmuber to identify the drive /){ DSTATUS stat; int result; switch (pdrv) { case DEV_RAM : //result = RAM_disk_initialize(); // translate the reslut code here stat = STA_NOINIT; return stat; case DEV_MMC : //result = MMC_disk_initialize(); // translate the reslut code here PORT_Init(PORTB, PIN1, PORTB_PIN1_SD_CLK, 0); PORT_Init(PORTB, PIN2, PORTB_PIN2_SD_CMD, 1); PORT_Init(PORTB, PIN3, PORTB_PIN3_SD_D0, 1); PORT_Init(PORTB, PIN4, PORTB_PIN4_SD_D1, 1); PORT_Init(PORTB, PIN5, PORTB_PIN5_SD_D2, 1); PORT_Init(PORTB, PIN6, PORTB_PIN6_SD_D3, 1); result = SDIO_Init(10000000); if(result == SD_RES_OK) { stat = RES_OK; sd_initialized = 1; } else { stat = STA_NOINIT; sd_initialized = 0; } return stat; case DEV_USB : //result = USB_disk_initialize(); // translate the reslut code here stat = STA_NOINIT; return stat; } return STA_NOINIT;}
读函数：
DRESULT disk_read ( BYTE pdrv, / Physical drive nmuber to identify the drive / BYTE buff, / Data buffer to store read data / LBA_t sector, / Start sector in LBA / UINT count / Number of sectors to read /){ DRESULT res; int result; switch (pdrv) { case DEV_RAM : // translate the arguments here //result = RAM_disk_read(buff, sector, count); // translate the reslut code here res = RES_PARERR; return res; case DEV_MMC : if(count == 1) { result = SDIO_BlockRead(sector, (uint32_t )buff); } else { //result = SDIO_MultiBlockRead(sector, count, (uint32_t )buff); result = SDIO_DMABlockRead(sector, count, (uint32_t )buff);//利用DMA或非DMA模式均可 } if(result == SD_RES_OK) res = RES_OK; else res = RES_ERROR; return res; case DEV_USB : // translate the arguments here //result = USB_disk_read(buff, sector, count); // translate the reslut code here res = RES_PARERR; return res; } return RES_PARERR;}
写函数：
DRESULT disk_write ( BYTE pdrv, / Physical drive nmuber to identify the drive / const BYTE buff, / Data to be written / LBA_t sector, / Start sector in LBA / UINT count / Number of sectors to write /){ DRESULT res; int result; switch (pdrv) { case DEV_RAM : // translate the arguments here //result = RAM_disk_write(buff, sector, count); // translate the reslut code here res = RES_PARERR; return res; case DEV_MMC : if(count == 1) { result = SDIO_BlockWrite(sector, (uint32_t )buff); } else { //result = SDIO_MultiBlockWrite(sector, count, (uint32_t )buff); result = SDIO_DMABlockWrite(sector, count, (uint32_t )buff);//利用DMA或非DMA模式均可 } if(result == SD_RES_OK) res = RES_OK; else res = RES_ERROR; return res; case DEV_USB : // translate the arguments here //result = USB_disk_write(buff, sector, count); // translate the reslut code here res = RES_PARERR; return res; } return RES_PARERR;}
还有一个函数是用户获取SD卡容量等信息的，如下：
DRESULT disk_ioctl ( BYTE pdrv, / Physical drive nmuber (0..) / BYTE cmd, / Control code / void buff / Buffer to send/receive control data /){ DRESULT res; //int result; switch (pdrv) { case DEV_RAM : // Process of the command for the RAM drive res = RES_PARERR; return res; case DEV_MMC : switch ( cmd ) { //fatfs内核利用cmd调用 case GET_SECTOR_COUNT: //sector count (DWORD)buff = SD_cardInfo.CardCapacity / 512; return RES_OK; case GET_SECTOR_SIZE: //sector size, 传入block size(SD),单位bytes (DWORD)buff = 512; return RES_OK; case GET_BLOCK_SIZE: //block size, 由上文可得，对付SD2.0卡最大8192，最小 1 (DWORD)buff = 1; //单位为 sector(FatFs) return RES_OK; case CTRL_SYNC: //同步命令，貌似FatFs内核用来判断写操作是否完成 return RES_OK; } res = RES_OK; return res; case DEV_USB : // Process of the command the USB drive res = RES_PARERR; return res; } return RES_PARERR;}
接口部分实现后，就可以调用干系的函数实现文件的读写了，测试程序如下：
res = f_mount(&fatfs, "sd:", 1);if(res != FR_OK){ printf("sdcard init fail!\r\n");}res = f_open(&filw, "sd:test.txt", FA_CREATE_ALWAYS | FA_WRITE);if(res != FR_OK){ printf("create file fail!\r\n");}res = f_write(&filw, str, strlen(str), &len);if(res != FR_OK){ printf("write file fail!\r\n");}f_close(&filw);
文件系统的配置可以在"ffconf.h"文件中根据实际需求进行修正。
