2021年12月31日 | 基于51单片机的SD卡读卡器MMC存储器

硬件设计

程序设计

#include

#define F_OSC  11059200//晶振平率Hz

#define F_BAUD 9600

#define RELOAD 256-F_OSC/12/32/F_BAUD

#define CR 0x0D        //回车

//定义SD卡需要的4根信号线

sbit SD_CLK = P1^4;

sbit SD_DI  = P1^6;

sbit SD_DO  = P1^5;

sbit SD_CS  = P1^7;

unsigned char xdata DATA[512];

//定义512字节缓冲区，注意需要使用 xdata关键字

//===========================================================

//写一字节到SD卡,模拟SPI总线方式

void SdWrite(unsigned char n)

{

    unsigned char i;

    for(i=8;i;i--)

    {

        SD_CLK=0;

        SD_DI=(n&0x80);

        n<<=1;

        SD_CLK=1;

        }

        SD_DI=1; 

    } 

//===========================================================

//从SD卡读一字节,模拟SPI总线方式

unsigned char SdRead()

{

    unsigned char n,i;

    for(i=8;i;i--)

    {

        SD_CLK=0;

        SD_CLK=1;

        n<<=1;

        if(SD_DO) n|=1;

    }

    return n;

}

//============================================================

//检测SD卡的响应

unsigned char SdResponse()

{

    unsigned char i=0,response;

    while(i<=8)

    {

        response = SdRead();

        if(response==0x00)

        break;

        if(response==0x01)

        break;

        i++;

    }

    return response;

} 

//================================================================

//发命令到SD卡

void SdCommand(unsigned char command, unsigned long argument, unsigned char CRC)

{

    SdWrite(command|0x40);

    SdWrite(((unsigned char *)&argument)[0]);

    SdWrite(((unsigned char *)&argument)[1]);

    SdWrite(((unsigned char *)&argument)[2]);

    SdWrite(((unsigned char *)&argument)[3]);

    SdWrite(CRC);

}

//================================================================

//初始化SD卡

unsigned char SdInit(void)

{

    int delay=0, trials=0;

    unsigned char i;

    unsigned char response=0x01;

    SD_CS=1;

    for(i=0;i<=9;i++)

    SdWrite(0xff);

    SD_CS=0;

    //Send Command 0 to put MMC in SPI mode

    SdCommand(0x00,0,0x95);

    response=SdResponse();

    if(response!=0x01)

    {

        return 0;

    } 

    while(response==0x01)

    {

        SD_CS=1;

        SdWrite(0xff);

        SD_CS=0;

        SdCommand(0x01,0x00ffc000,0xff);

        response=SdResponse();

    } 

    SD_CS=1;

    SdWrite(0xff);

    return 1; 

}

//================================================================

//往SD卡指定地址写数据,一次最多512字节

unsigned char SdWriteBlock(unsigned char *Block, unsigned long address,int len)

{

    unsigned int count;

    unsigned char dataResp;

    //Block size is 512 bytes exactly

    //First Lower SS

    SD_CS=0;

    //Then send write command

    SdCommand(0x18,address,0xff);

    if(SdResponse()==00)

    {

        SdWrite(0xff);

        SdWrite(0xff);

        SdWrite(0xff);

        //command was a success - now send data

        //start with DATA TOKEN = 0xFE

        SdWrite(0xfe);

        //now send data

        for(count=0;count        

        for(;count<512;count++) SdWrite(0);

        //data block sent - now send checksum

        SdWrite(0xff); //两字节CRC校验, 为0XFFFF 表示不考虑CRC

        SdWrite(0xff);

        //Now read in the DATA RESPONSE token

        dataResp=SdRead();

        //Following the DATA RESPONSE token

        //are a number of BUSY bytes

        //a zero byte indicates the MMC is busy

        while(SdRead()==0);

        dataResp=dataResp&0x0f; //mask the high byte of the DATA RESPONSE token

        SD_CS=1;

        SdWrite(0xff);

        if(dataResp==0x0b)

        {

        //printf("DATA WAS NOT ACCEPTED BY CARD -- CRC ERRORn");

        return 0;

        }

        if(dataResp==0x05)

        return 1;

        //printf("Invalid data Response token.n");

        return 0;

    }

    //printf("Command 0x18 (Write) was not received by the MMC.n");

    return 0;

}

文件仅供参考

链接：https://pan.baidu.com/s/1h3ZnGUPP5o_8_NsVMwVQuA

提取码：4ebs