官方的软件包已经包含了SD卡的驱动
STM32Cube_FW_F7_V1.9.0\Drivers\BSP\STM32F769I-Discovery\stm32f769i_discovery_sd.c

现对主要的函数理解以加深对SDIO的认识，为以后的使用积累经验。

根据电路图可知硬件连接上三个数据线，一根命令传输线，一根时钟线，一根SD卡插入检测线。

1. SD_HandleTypeDef uSdHandle;
   
2. /**
   
3.   * @brief  Initializes the SD card device.
   
4.   * @retval SD status
   
5.   */
   
6. uint8_t BSP_SD_Init(void)
   
7. {
   
8.   uint8_t sd_state = MSD_OK;
   
9. 
   
10.   /* PLLSAI is dedicated to LCD periph. Do not use it to get 48MHz*/
    
11. 
    
12.   /* uSD device interface configuration */
    
13.     uSdHandle.Instance = SDMMC2;
    
14.     uSdHandle.Init.ClockEdge           = SDMMC_CLOCK_EDGE_RISING;
    
15.     uSdHandle.Init.ClockBypass         = SDMMC_CLOCK_BYPASS_DISABLE;
    
16.     uSdHandle.Init.ClockPowerSave      = SDMMC_CLOCK_POWER_SAVE_DISABLE;
    
17.     uSdHandle.Init.BusWide             = SDMMC_BUS_WIDE_1B;
    
18.     uSdHandle.Init.HardwareFlowControl = SDMMC_HARDWARE_FLOW_CONTROL_DISABLE;
    
19.     uSdHandle.Init.ClockDiv            = SDMMC_TRANSFER_CLK_DIV;
    
20. 
    
21.   /* Msp SD Detect pin initialization */
    
22.   BSP_SD_Detect_MspInit(&uSdHandle, NULL);
    
23.   if(BSP_SD_IsDetected() != SD_PRESENT)   /* Check if SD card is present */
    
24.   {
    
25.     return MSD_ERROR_SD_NOT_PRESENT;
    
26.   }
    
27. 
    
28.   /* Msp SD initialization */
    
29.   BSP_SD_MspInit(&uSdHandle, NULL);
    
30. 
    
31.   /* HAL SD initialization */
    
32.   if(HAL_SD_Init(&uSdHandle) != HAL_OK)
    
33.   {
    
34.     sd_state = MSD_ERROR;
    
35.   }
    
36. 
    
37.   /* Configure SD Bus width */
    
38.   if(sd_state == MSD_OK)
    
39.   {
    
40.     /* Enable wide operation */
    
41.     if(HAL_SD_ConfigWideBusOperation(&uSdHandle, SDMMC_BUS_WIDE_4B) != HAL_OK)
    
42.     {
    
43.       sd_state = MSD_ERROR;
    
44.     }
    
45.     else
    
46.     {
    
47.       sd_state = MSD_OK;
    
48.     }
    
49.   }
    
50.   return  sd_state;
    
51. }

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代码初始化时设置数据位宽为SDMMC_BUS_WIDE_1B，之后又设置为SDMMC_BUS_WIDE_4B，为什么不一开始就设置成4位，而且硬件原理图上也是按照4位模式接的，后来在编程手册上找到如下描述，需要初始化完成之后再设置位宽度，但是还是没有想明白为什么这么设计。

By default SDMMC_D0 is used for data transfer. After initialization, the host can change the databus width.

BSP_SD_IsDetected()函数根据代码注释和内容可判断是，检测SD卡是否插入,检测到低电平是代表SD卡已插入。

1. /**
   
2. * @brief  Detects if SD card is correctly plugged in the memory slot or not.
   
3. * @retval Returns if SD is detected or not
   
4. */
   
5. uint8_t BSP_SD_IsDetected(void)
   
6. {
   
7.   __IO uint8_t  status = SD_PRESENT;
   
8. 
   
9.   /* Check SD card detect pin */
   
10.   if (HAL_GPIO_ReadPin(SD_DETECT_GPIO_PORT, SD_DETECT_PIN) == GPIO_PIN_SET)
    
11.   {
    
12.     status = SD_NOT_PRESENT;
    
13.   }
    
14. 
    
15.     return status;
    
16. }

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  BSP_SD_Detect_MspInit(&uSdHandle, NULL); 配置sd卡插入检测引脚为输入上拉模式

1. /**
   
2.   * @brief  Initializes the SD Detect pin MSP.
   
3.   * @param  hsd: SD handle
   
4.   * @param  Params : pointer on additional configuration parameters, can be NULL.  
   
5.   * @retval None
   
6.   */
   
7. __weak void BSP_SD_Detect_MspInit(SD_HandleTypeDef *hsd, void *Params)
   
8. {
   
9.   GPIO_InitTypeDef  gpio_init_structure;
   
10. 
    
11.   SD_DETECT_GPIO_CLK_ENABLE();
    
12. 
    
13.   /* GPIO configuration in input for uSD_Detect signal */
    
14.   gpio_init_structure.Pin       = SD_DETECT_PIN;
    
15.   gpio_init_structure.Mode      = GPIO_MODE_INPUT;
    
16.   gpio_init_structure.Pull      = GPIO_PULLUP;
    
17.   gpio_init_structure.Speed     = GPIO_SPEED_HIGH;
    
18.   HAL_GPIO_Init(SD_DETECT_GPIO_PORT, &gpio_init_structure);
    
19. }

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1. /**
   
2.   * @brief  Initializes the SD Card.
   
3.   * @param  hsd Pointer to SD handle
   
4.   * @note   This function initializes the SD card. It could be used when a card
   
5.             re-initialization is needed.
   
6.   * @retval HAL status
   
7.   */
   
8. HAL_StatusTypeDef HAL_SD_InitCard(SD_HandleTypeDef *hsd)
   
9. {
   
10.   uint32_t errorstate = HAL_SD_ERROR_NONE;
    
11.   SD_InitTypeDef Init;
    
12.   
    
13.   /* Default SDMMC peripheral configuration for SD card initialization */
    
14.   Init.ClockEdge           = SDMMC_CLOCK_EDGE_RISING;
    
15.   Init.ClockBypass         = SDMMC_CLOCK_BYPASS_DISABLE;
    
16.   Init.ClockPowerSave      = SDMMC_CLOCK_POWER_SAVE_DISABLE;
    
17.   Init.BusWide             = SDMMC_BUS_WIDE_1B;
    
18.   Init.HardwareFlowControl = SDMMC_HARDWARE_FLOW_CONTROL_DISABLE;
    
19.   Init.ClockDiv            = SDMMC_INIT_CLK_DIV;
    
20. 
    
21.   /* Initialize SDMMC peripheral interface with default configuration */
    
22.   SDMMC_Init(hsd->Instance, Init);
    
23. 
    
24.   /* Disable SDMMC Clock */
    
25.   __HAL_SD_DISABLE(hsd);
    
26.   
    
27.   /* Set Power State to ON */
    
28.   SDMMC_PowerState_ON(hsd->Instance);
    
29.   
    
30.   /* Enable SDMMC Clock */
    
31.   __HAL_SD_ENABLE(hsd);
    
32.   
    
33.   /* Required power up waiting time before starting the SD initialization sequence */
    
34.   HAL_Delay(2);
    
35.   
    
36.   /* Identify card operating voltage */
    
37.   errorstate = SD_PowerON(hsd);
    
38.   if(errorstate != HAL_SD_ERROR_NONE)
    
39.   {
    
40.     hsd->State = HAL_SD_STATE_READY;
    
41.     hsd->ErrorCode |= errorstate;
    
42.     return HAL_ERROR;
    
43.   }
    
44. 
    
45.   /* Card initialization */
    
46.   errorstate = SD_InitCard(hsd);
    
47.   if(errorstate != HAL_SD_ERROR_NONE)
    
48.   {
    
49.     hsd->State = HAL_SD_STATE_READY;
    
50.     hsd->ErrorCode |= errorstate;
    
51.     return HAL_ERROR;
    
52.   }
    
53. 
    
54.   return HAL_OK;
    
55. }

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呃呃呃  没编辑完  竟然发出去了  有时间慢慢写吧

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