STM32 通过SPI模式实现SD卡 读卡器

实现SD卡读卡器的步骤如下：

1. 硬件连接：将SD卡读卡器的MISO、MOSI、SCK、CS（片选）引脚分别连接到STM32的SPI接口的MISO、MOSI、SCK、NSS（片选）引脚上。

2. 初始化SPI接口：初始化SPI接口，设置SPI模式、数据位数、时钟极性和相位等参数。

3. 初始化SD卡：通过SPI接口发送SD卡的初始化命令，等待SD卡响应，并设置SD卡的工作参数。

4. 读取数据：通过SPI接口发送读数据命令，读取数据。

具体代码实现如下：

#include "stm32f4xx.h"

/* 定义SPI接口和引脚 */
#define SPIx_SPI                       SPI2
#define SPIx_CLK                       RCC_APB1Periph_SPI2
#define SPIx_IRQn                      SPI2_IRQn
#define SPIx_IRQHANDLER                SPI2_IRQHandler
#define SPIx_SCK_PIN                   GPIO_Pin_13
#define SPIx_SCK_GPIO_PORT             GPIOB
#define SPIx_SCK_GPIO_CLK              RCC_AHB1Periph_GPIOB
#define SPIx_MISO_PIN                  GPIO_Pin_14
#define SPIx_MISO_GPIO_PORT            GPIOB
#define SPIx_MISO_GPIO_CLK             RCC_AHB1Periph_GPIOB
#define SPIx_MOSI_PIN                  GPIO_Pin_15
#define SPIx_MOSI_GPIO_PORT            GPIOB
#define SPIx_MOSI_GPIO_CLK             RCC_AHB1Periph_GPIOB
#define SPIx_CS_PIN                    GPIO_Pin_12
#define SPIx_CS_GPIO_PORT              GPIOB
#define SPIx_CS_GPIO_CLK               RCC_AHB1Periph_GPIOB

/* 定义SD卡命令 */
#define CMD0                           0x40
#define CMD8                           0x48
#define CMD9                           0x49
#define CMD16                          0x50
#define CMD17                          0x51
#define CMD55                          0x77
#define CMD58                          0x7A
#define ACMD41                         0x69

/* 定义SD卡响应 */
#define R1                             0x01
#define R1_IDLE_STATE                  0x01
#define R1_ILLEGAL_COMMAND             0x04
#define R1_CRC_ERROR                   0x08
#define R1_ERASE_RESET                 0x20
#define R1_IN_IDLE_STATE               0x80

/* SD卡初始化函数 */
uint8_t SD_Init(void)
{
    uint8_t i, response, data[4];

    /* 初始化SPI接口 */
    SPI_InitTypeDef SPI_InitStructure;
    GPIO_InitTypeDef GPIO_InitStructure;
    RCC_AHB1PeriphClockCmd(SPIx_SCK_GPIO_CLK | SPIx_MISO_GPIO_CLK | SPIx_MOSI_GPIO_CLK, ENABLE);
    RCC_APB1PeriphClockCmd(SPIx_CLK, ENABLE);
    GPIO_PinAFConfig(SPIx_SCK_GPIO_PORT, GPIO_PinSource13, GPIO_AF_SPI2);
    GPIO_PinAFConfig(SPIx_MISO_GPIO_PORT, GPIO_PinSource14, GPIO_AF_SPI2);
    GPIO_PinAFConfig(SPIx_MOSI_GPIO_PORT, GPIO_PinSource15, GPIO_AF_SPI2);
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_NOPULL;
    GPIO_InitStructure.GPIO_Pin = SPIx_SCK_PIN;
    GPIO_Init(SPIx_SCK_GPIO_PORT, &GPIO_InitStructure);
    GPIO_InitStructure.GPIO_Pin = SPIx_MISO_PIN;
    GPIO_Init(SPIx_MISO_GPIO_PORT, &GPIO_InitStructure);
    GPIO_InitStructure.GPIO_Pin = SPIx_MOSI_PIN;
    GPIO_Init(SPIx_MOSI_GPIO_PORT, &GPIO_InitStructure);
    SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
    SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;
    SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low;
    SPI_InitStructure.SPI_CPHA = SPI_CPHA_1Edge;
    SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;
    SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_256;
    SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
    SPI_InitStructure.SPI_CRCPolynomial = 7;
    SPI_Init(SPIx_SPI, &SPI_InitStructure);
    SPI_Cmd(SPIx_SPI, ENABLE);

    /* 等待SD卡上电 */
    for(i = 0; i < 10; i++)
    {
        SPIx_WriteByte(0xFF);
    }

    /* 发送CMD0命令 */
    response = SD_SendCommand(CMD0, 0x00000000, R1_IDLE_STATE);
    if(response != R1_IDLE_STATE)
    {
        return 1;
    }

    /* 发送CMD8命令 */
    response = SD_SendCommand(CMD8, 0x000001AA, R1_IDLE_STATE);
    if(response == R1_IDLE_STATE)
    {
        for(i = 0; i < 4; i++)
        {
            data[i] = SPIx_WriteByte(0xFF);
        }
        if((data[2] != 0x01) || (data[3] != 0xAA))
        {
            return 1;
        }
    }

    /* 发送ACMD41命令 */
    while(1)
    {
        response = SD_SendCommand(CMD55, 0x00000000, R1_IDLE_STATE);
        if(response != R1_IDLE_STATE)
        {
            return 1;
        }
        response = SD_SendCommand(ACMD41, 0x40000000, R1_IDLE_STATE);
        if(response == R1_IDLE_STATE)
        {
            break;
        }
    }

    /* 发送CMD58命令 */
    response = SD_SendCommand(CMD58, 0x00000000, R1_IDLE_STATE);
    if(response != R1_IDLE_STATE)
    {
        return 1;
    }
    for(i = 0; i < 4; i++)
    {
        data[i] = SPIx_WriteByte(0xFF);
    }

    return 0;
}

/* 发送SD卡命令 */
uint8_t SD_SendCommand(uint8_t cmd, uint32_t arg, uint8_t crc)
{
    uint8_t response;

    /* 发送命令 */
    SPIx_WriteByte(cmd | 0x40);
    SPIx_WriteByte((uint8_t)(arg >> 24));
    SPIx_WriteByte((uint8_t)(arg >> 16));
    SPIx_WriteByte((uint8_t)(arg >> 8));
    SPIx_WriteByte((uint8_t)arg);
    SPIx_WriteByte(crc);

    /* 接收响应 */
    response = SPIx_WriteByte(0xFF);
    while(response == 0xFF)
    {
        response = SPIx_WriteByte(0xFF);
    }

    return response;
}

/* 读取SD卡数据 */
void SD_ReadData(uint32_t sector, uint8_t *buffer)
{
    uint32_t i;
    uint8_t response;

    /* 发送CMD17命令 */
    response = SD_SendCommand(CMD17, sector << 9, R1);
    if(response != 0x00)
    {
        return;
    }

    /* 读取数据 */
    for(i = 0; i < 512; i++)
    {
        buffer[i] = SPIx_WriteByte(0xFF);
    }

    /* 停止传输 */
    SPIx_WriteByte(0xFF);
    SPIx_WriteByte(0xFF);
}

/* SPI接口写入一个字节 */
uint8_t SPIx_WriteByte(uint8_t byte)
{
    while(SPI_I2S_GetFlagStatus(SPIx_SPI, SPI_I2S_FLAG_TXE) == RESET);
    SPI_I2S_SendData(SPIx_SPI, byte);
    while(SPI_I2S_GetFlagStatus(SPIx_SPI, SPI_I2S_FLAG_RXNE) == RESET);
    return SPI_I2S_ReceiveData(SPIx_SPI);
}

注：以上代码仅供参考，实际使用时需要根据具体情况进行调整。