SD 卡 SPI 模式初始化过程，带流程图。

只看该作者 · 2012-2-3 14:37

流程图如下，该代码能识别 MMC V3, SD V1.X 和 SD V2.00及其后续版本，其中 SD V2.00及其后续版本又可分为标准容量和大容量版本。

只看该作者 · 2012-2-3 14:46

SD SPI 发送命令 API 如下，所有实现代码参考附件。

/**
  * @brief  Send 6 bytes command to the SD card.
  * @param  Cmd: The command send to SD card.
  * @param  argument: The command argument.
  * @param  response_type: the SPI command response type.
  * @param  *response: the SPI response returned.
  * @retval The SD Response.
  */
uint8_t ARC_sd_send_command(uint8_t cmd, uint32_t argument,
                        SD_Response response_type, uint8_t *response)
{
int32_t i = 0;
uint8_t crc = 0x01;
int8_t response_length = 0;
uint8_t tmp;
uint8_t Frame[6];
if (cmd & 0x80)  /* Send a CMD55 prior to ACMD<n> */
{
      cmd &= 0x7F;
      ARC_sd_send_command(SD_CMD_APP_CMD, 0, R1, response);
      if (response[0] > 0x1)
      {
         ARC_SD_CS_HIGH();
         ARC_SPI_SendByte(SPI1, SD_DUMMY_BYTE);
         return response[0];
      }
}
ARC_SD_CS_LOW();
if(cmd == SD_CMD_GO_IDLE_STATE)
      crc = 0x95;

if(cmd == SD_CMD_SEND_IF_COND)
      crc = 0x87;

/* All data is sent MSB first, and MSb first */
/* cmd Format:
cmd[7:6] : 01
cmd[5:0] : command */
Frame[0] = ((cmd & 0x3F) | 0x40); /*!< Construct byte 1 */
Frame[1] = (uint8_t)(argument >> 24); /*!< Construct byte 2 */
Frame[2] = (uint8_t)(argument >> 16); /*!< Construct byte 3 */
Frame[3] = (uint8_t)(argument >> 8); /*!< Construct byte 4 */
Frame[4] = (uint8_t)(argument); /*!< Construct byte 5 */
Frame[5] = (uint8_t)(crc); /*!< Construct CRC: byte 6 */
for (i = 0; i < 6; i++)
{
      ARC_SPI_SendByte(SPI1, Frame[i]); /*!< Send the Cmd bytes */
}

switch (response_type)
{
      case R1:
      case R1B:
         response_length = 1;
         break;
      case R2:
         response_length = 2;
         break;
      case R3:
      case R7:
         response_length = 5;
         break;
      default:
         break;
}

/* Wait for a response. A response can be recognized by the start bit (a zero) */
i = 0xFF;
do
{
      tmp = ARC_SPI_SendByte(SPI1, SD_DUMMY_BYTE);
}while ((tmp & 0x80) && --i);
response[0] = tmp;

/* Just bail if we never got a response */
if (i == 0)
{
      ARC_SD_CS_HIGH();
      ARC_SPI_SendByte(SPI1, SD_DUMMY_BYTE);
      return response[0];
}
if((response[0] & SD_ILLEGAL_COMMAND) == SD_ILLEGAL_COMMAND)
{
      ARC_SD_CS_HIGH();
      ARC_SPI_SendByte(SPI1, SD_DUMMY_BYTE);
      return response[0];
}
i = 1;
while(i < response_length)
{
      tmp = ARC_SPI_SendByte(SPI1, SD_DUMMY_BYTE);
      response[i] = tmp;
      i++;
}

/* If the response is a "busy" type (R1B), then there's some
   * special handling that needs to be done. The card will
   * output a continuous stream of zeros, so the end of the BUSY
   * state is signaled by any nonzero response. The bus idles
   * high.
   */
if (response_type == R1B)
{
      do
      {
         tmp = ARC_SPI_SendByte(SPI1, SD_DUMMY_BYTE);;
      }while (tmp != 0xFF);
      ARC_SPI_SendByte(SPI1, SD_DUMMY_BYTE);
}

ARC_SD_CS_HIGH();
ARC_SPI_SendByte(SPI1, SD_DUMMY_BYTE);
return response[0];
}