解决STM32 SD卡官方库移植时 获取不到SD Status寄存器值的问题

前言

1. SD卡内部的SD Status寄存器和Card Status寄存器从名字上来看好像都是状态寄存器，但实际上所要呈现的工程是不同的，这一点要注意；
2. 本博文主要说内容是怎样正确的获取SD Status寄存器的值；
3. 如有不足之处，还请多多指教；

问题

SD Status寄存器表如下，我想获取其中的AU_SIZE的值

（[400:0]这段位域内没有信息，我这里忽略了）
如下图，AU_SIZE的值本身应该在0x01~0x09之间，但是我用串口打印出来的值却是0；

获取SD Status寄存器的函数代码如下：

/** 
  * @brief SD Card Status 
  */
typedef struct
{
  __IO uint8_t DAT_BUS_WIDTH;
  __IO uint8_t SECURED_MODE;
  __IO uint16_t SD_CARD_TYPE;
  __IO uint32_t SIZE_OF_PROTECTED_AREA;
  __IO uint8_t SPEED_CLASS;
  __IO uint8_t PERFORMANCE_MOVE;
  __IO uint8_t AU_SIZE;
  __IO uint16_t ERASE_SIZE;
  __IO uint8_t ERASE_TIMEOUT;
  __IO uint8_t ERASE_OFFSET;
} SD_CardStatus;

static uint8_t SDSTATUS_Tab[16];                            //SD状态表
SD_CardStatus SDCardStatus;

/**
  * @brief  Enables wide bus opeartion for the requeseted card if supported by 
  *         card.
  * @param  WideMode: Specifies the SD card wide bus mode. 
  *   This parameter can be one of the following values:
  *     @arg SDIO_BusWide_8b: 8-bit data transfer (Only for MMC)
  *     @arg SDIO_BusWide_4b: 4-bit data transfer
  *     @arg SDIO_BusWide_1b: 1-bit data transfer
  * @retval SD_Error: SD Card Error code.
  */
SD_Error SD_GetCardStatus(SD_CardStatus *cardstatus)
{
  SD_Error errorstatus = SD_OK;
  uint8_t tmp = 0;
  

  errorstatus = SD_SendSDStatus((uint32_t *)SDSTATUS_Tab); //程序卡死在这个函数里； 

  if (errorstatus  != SD_OK)
  {
    return(errorstatus);
  }

  /*!< Byte 0 */
  tmp = (uint8_t)((SDSTATUS_Tab[0] & 0xC0) >> 6);
  cardstatus->DAT_BUS_WIDTH = tmp;

  /*!< Byte 0 */
  tmp = (uint8_t)((SDSTATUS_Tab[0] & 0x20) >> 5);
  cardstatus->SECURED_MODE = tmp;

  /*!< Byte 2 */
  tmp = (uint8_t)((SDSTATUS_Tab[2] & 0xFF));
  cardstatus->SD_CARD_TYPE = tmp << 8;

  /*!< Byte 3 */
  tmp = (uint8_t)((SDSTATUS_Tab[3] & 0xFF));
  cardstatus->SD_CARD_TYPE |= tmp;

  /*!< Byte 4 */
  tmp = (uint8_t)(SDSTATUS_Tab[4] & 0xFF);
  cardstatus->SIZE_OF_PROTECTED_AREA = tmp << 24;

  /*!< Byte 5 */
  tmp = (uint8_t)(SDSTATUS_Tab[5] & 0xFF);
  cardstatus->SIZE_OF_PROTECTED_AREA |= tmp << 16;

  /*!< Byte 6 */
  tmp = (uint8_t)(SDSTATUS_Tab[6] & 0xFF);
  cardstatus->SIZE_OF_PROTECTED_AREA |= tmp << 8;

  /*!< Byte 7 */
  tmp = (uint8_t)(SDSTATUS_Tab[7] & 0xFF);
  cardstatus->SIZE_OF_PROTECTED_AREA |= tmp;

  /*!< Byte 8 */
  tmp = (uint8_t)((SDSTATUS_Tab[8] & 0xFF));
  cardstatus->SPEED_CLASS = tmp;

  /*!< Byte 9 */
  tmp = (uint8_t)((SDSTATUS_Tab[9] & 0xFF));
  cardstatus->PERFORMANCE_MOVE = tmp;

  /*!< Byte 10 */
  tmp = (uint8_t)((SDSTATUS_Tab[10] & 0xF0) >> 4);
  cardstatus->AU_SIZE = tmp;

  /*!< Byte 11 */
  tmp = (uint8_t)(SDSTATUS_Tab[11] & 0xFF);
  cardstatus->ERASE_SIZE = tmp << 8;

  /*!< Byte 12 */
  tmp = (uint8_t)(SDSTATUS_Tab[12] & 0xFF);
  cardstatus->ERASE_SIZE |= tmp;

  /*!< Byte 13 */
  tmp = (uint8_t)((SDSTATUS_Tab[13] & 0xFC) >> 2);
  cardstatus->ERASE_TIMEOUT = tmp;

  /*!< Byte 13 */
  tmp = (uint8_t)((SDSTATUS_Tab[13] & 0x3));
  cardstatus->ERASE_OFFSET = tmp;
 
  return(errorstatus);
}


/**
  * @brief  Returns the current SD card's status.
  * @param  psdstatus: pointer to the buffer that will contain the SD card status 
  *         (SD Status register).
  * @retval SD_Error: SD Card Error code.
  */
SD_Error SD_SendSDStatus(uint32_t *psdstatus)
{
  SD_Error errorstatus = SD_OK;
  uint32_t count = 0;

  if (SDIO_GetResponse(SDIO_RESP1) & SD_CARD_LOCKED)
  {
    errorstatus = SD_LOCK_UNLOCK_FAILED;
    return(errorstatus);
  }

	//CMD7 这个是我自己加的，在获取SD_Status寄存器值之前，卡必须处于传输状态“tran_state”
	SDIO_CmdInitStructure.SDIO_Argument = (uint32_t) RCA << 16;
  SDIO_CmdInitStructure.SDIO_CmdIndex = SD_CMD_SEL_DESEL_CARD;
  SDIO_CmdInitStructure.SDIO_Response = SDIO_Response_Short;   //r1
  SDIO_CmdInitStructure.SDIO_Wait = SDIO_Wait_No;
  SDIO_CmdInitStructure.SDIO_CPSM = SDIO_CPSM_Enable;
  SDIO_SendCommand(&SDIO_CmdInitStructure);

  errorstatus = CmdResp1Error(SD_CMD_SET_BLOCKLEN);

  if (SD_OK != errorstatus)
  {
    return(errorstatus);
  }

	/*!< Set Block Size for Card，cmd16,若是sdsc卡，可以用来设置块大小，若是sdhc卡，块大小为512字节，不受cmd16影响 */
  SDIO_CmdInitStructure.SDIO_Argument = 512;
  SDIO_CmdInitStructure.SDIO_CmdIndex = SD_CMD_SET_BLOCKLEN;
  SDIO_CmdInitStructure.SDIO_Response = SDIO_Response_Short;   //r1
  SDIO_CmdInitStructure.SDIO_Wait = SDIO_Wait_No;
  SDIO_CmdInitStructure.SDIO_CPSM = SDIO_CPSM_Enable;
  SDIO_SendCommand(&SDIO_CmdInitStructure);

  errorstatus = CmdResp1Error(SD_CMD_SET_BLOCKLEN);

  if (SD_OK != errorstatus)
  {
    return(errorstatus);
  }
  
  /*!< CMD55 */
  SDIO_CmdInitStructure.SDIO_Argument = (uint32_t) RCA << 16;
  SDIO_CmdInitStructure.SDIO_CmdIndex = SD_CMD_APP_CMD;
  SDIO_CmdInitStructure.SDIO_Response = SDIO_Response_Short;
  SDIO_CmdInitStructure.SDIO_Wait = SDIO_Wait_No;
  SDIO_CmdInitStructure.SDIO_CPSM = SDIO_CPSM_Enable;
  SDIO_SendCommand(&SDIO_CmdInitStructure);
  errorstatus = CmdResp1Error(SD_CMD_APP_CMD);

  if (errorstatus != SD_OK)
  {
    return(errorstatus);
  }

  SDIO_DataInitStructure.SDIO_DataTimeOut = SD_DATATIMEOUT;
  SDIO_DataInitStructure.SDIO_DataLength = 64;
  SDIO_DataInitStructure.SDIO_DataBlockSize = SDIO_DataBlockSize_64b;
  SDIO_DataInitStructure.SDIO_TransferDir = SDIO_TransferDir_ToSDIO;
  SDIO_DataInitStructure.SDIO_TransferMode = SDIO_TransferMode_Block;
  SDIO_DataInitStructure.SDIO_DPSM = SDIO_DPSM_Enable;
  SDIO_DataConfig(&SDIO_DataInitStructure);

  /*!< Send ACMD13 SD_APP_STAUS  with argument as card's RCA.*/
  SDIO_CmdInitStructure.SDIO_Argument = 0;
  SDIO_CmdInitStructure.SDIO_CmdIndex = SD_CMD_SD_APP_STAUS;
  SDIO_CmdInitStructure.SDIO_Response = SDIO_Response_Short;
  SDIO_CmdInitStructure.SDIO_Wait = SDIO_Wait_No;
  SDIO_CmdInitStructure.SDIO_CPSM = SDIO_CPSM_Enable;
  SDIO_SendCommand(&SDIO_CmdInitStructure);
  errorstatus = CmdResp1Error(SD_CMD_SD_APP_STAUS);

  if (errorstatus != SD_OK)
  {
    return(errorstatus);
  }

  while (!(SDIO->STA &(SDIO_FLAG_RXOVERR | SDIO_FLAG_DCRCFAIL | SDIO_FLAG_DTIMEOUT | SDIO_FLAG_DBCKEND | SDIO_FLAG_STBITERR)))
  {
    if (SDIO_GetFlagStatus(SDIO_FLAG_RXFIFOHF) != RESET)
    {
      for (count = 0; count < 8; count++)
      {
        *(psdstatus + count) = SDIO_ReadData();
      }
      psdstatus += 8;
    }
  }
	
  if (SDIO_GetFlagStatus(SDIO_FLAG_DTIMEOUT) != RESET)
  {
    SDIO_ClearFlag(SDIO_FLAG_DTIMEOUT);
    errorstatus = SD_DATA_TIMEOUT;
    return(errorstatus);
  }
  else if (SDIO_GetFlagStatus(SDIO_FLAG_DCRCFAIL) != RESET)
  {
    SDIO_ClearFlag(SDIO_FLAG_DCRCFAIL);
    errorstatus = SD_DATA_CRC_FAIL;
    return(errorstatus);
  }
  else if (SDIO_GetFlagStatus(SDIO_FLAG_RXOVERR) != RESET)
  {
    SDIO_ClearFlag(SDIO_FLAG_RXOVERR);
    errorstatus = SD_RX_OVERRUN;
    return(errorstatus);
  }
  else if (SDIO_GetFlagStatus(SDIO_FLAG_STBITERR) != RESET)
  {
    SDIO_ClearFlag(SDIO_FLAG_STBITERR);
    errorstatus = SD_START_BIT_ERR;
    return(errorstatus);
  }

  while (SDIO_GetFlagStatus(SDIO_FLAG_RXDAVL) != RESET)
  {
    *psdstatus = SDIO_ReadData();
    psdstatus++;
  }

  /*!< Clear all the static status flags*/
  SDIO_ClearFlag(SDIO_STATIC_FLAGS);

  return(errorstatus);
}

我用JLink调试时候，发现函数在下面函数中执行死循环；

  while (!(SDIO->STA &(SDIO_FLAG_RXOVERR | SDIO_FLAG_DCRCFAIL | SDIO_FLAG_DTIMEOUT | SDIO_FLAG_DBCKEND | SDIO_FLAG_STBITERR)))
  {
    if (SDIO_GetFlagStatus(SDIO_FLAG_RXFIFOHF) != RESET)
    {
      for (count = 0; count < 8; count++)
      {
        *(psdstatus + count) = SDIO_ReadData();
      }
      psdstatus += 8;
    }
  }

但是问题并不是出在这里，而是在上面SD_Error SD_SendSDStatus(uint32_t *psdstatus)函数中，少了一个命令；
看下列图片中的红线标注意思是，要想获取SD Status寄存器的值，必须要使SD卡处于“传输状态”，也就是“tran_state”

也就是主机向SD卡发送CMD55+ACMD13之前，必须先判断当前SD卡目前的状态，可以用 SD_GetState()函数，函数会返回当前状态，我获取的是处于待机状态 SD_CARD_STANDBY，查阅装填装换机制如下图：

需要发送一个CMD7即可从SD_CARD_STANDBY模式转化为SD_CARD_TRANSFER模式，最终即可最终即可获得；CMD7代码我已经在上面的例程中写出来了；上面的代码是正确代码；实现的结果如下：

AU_SIZE = 0x09；正确；