单片机读写SD卡教程

郑重声明：本实验并不是对所有SD卡都能成功运行第一步：打开winhex软件，用读卡器读SD卡，在winhex中查看SD卡点这点击查找（ctrl+F）输入FAT（找到DBR处）发现DBR起始于0x11200扇区地址，它必是512整数倍，因为一个扇区含512BYTE，所以在程序中读一个扇区时一定要是512整数倍，否则会出错。

11200地址对应的值是0xEB，本程序读一下这个地址的值看看是否正确。

注意有的winhex编址是十进制看看程序吧#include <reg52.h>#define uchar unsigned char#define uint unsigned int//=============================================================//定义SD卡需要的4根信号线sbit SD_CLK = P1^1;sbit SD_DI = P1^2;sbit SD_DO = P1^0;sbit SD_CS = P1^3;sbit Beep=P2^0;//用来调程序标志//===========================================================//===========================================================//定义512字节缓冲区，，89C52直接定义成unsigned char DATA[80];，太大了RAM不够unsigned char xdata DATA[512];void delay(unsigned int z){unsigned int x,y;for(x=z;x>0;x--);for(y=110;y>0;y--);}//=========================================================== //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=1;SD_CLK=0;n<<=1;if(SD_DO) n|=1;}return n;}//============================================================ //检测SD卡的响应unsigned char SdResponse(){uchar i=0,response=0;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(argument>>24);SdWrite(argument>>16);SdWrite(argument>>8);SdWrite(argument);SdWrite(CRC);}//================================================================ //初始化SD卡unsigned char SdInit(void){unsigned char i;unsigned char response=0xFF;P3=0xff;SD_CS=1;for(i=0;i<=0xfe;i++)SdWrite(0xff);SD_CS=0;SdCommand(0x00,0,0x95);SD_DI=1;response=SdResponse();if(response!=0x01){return 0;}if(response==0x01){ //不管什么SD卡都能进入这一步，同时也说明硬件没问题SD_CS=1;//Beep=0;//while(1);//用来查看程序能否运行到这一步，去掉//即可SdWrite(0xff);SD_CS=0;while(1){SdCommand(0x01,0,0xff);//SdCommand(0x01,0x00000000,0xff);//进SPIresponse=0xff;SD_DI=1;for(i=0;i<250;i++)//response!=0x00//等待回复{response=SdResponse(); //Beep=0;/if(response==0) break;}if(response==0) {break;}//回复0则通过SPI，只要通过SPI后面的指令才能继//续// Beep=0;}// Beep=0;//看程序能否跳出来，挑不出来则进不了SPISD_CS=1;SdWrite(0xff);SD_CS=0;// Beep=0;return 1;}}//================================================================//往SD卡指定地址写数据,一次最多512字节最好不要乱写否则fat系统被改掉SD卡打不开unsigned char SdWriteBlock(unsigned char *Block, unsigned long address,int len){unsigned int count;unsigned char dataResp;SD_CS=0;SdCommand(0x18,address,0xff);if(SdResponse()==00){SdWrite(0xff);SdWrite(0xff);SdWrite(0xff);//command was a success - now send data//start with DATA TOKEN = 0xFESdWrite(0xfe);//now send datafor(count=0;count<len;count++) SdWrite(*Block++);for(;count<512;count++) SdWrite(0);//data block sent - now send checksumSdWrite(0xff); //两字节CRC校验, 为0XFFFF 表示不考虑CRCSdWrite(0xff);//Now read in the DA TA RESPONSE tokendataResp=SdRead();while(SdRead()==0);dataResp=dataResp&0x0f; //mask the high byte of the DATA RESPONSE tokenSD_CS=1;SdWrite(0xff);if(dataResp==0x0b){return 0;}if(dataResp==0x05)return 1;return 0;}//printf("Command 0x18 (Write) was not received by the SD.\n");return 0;}//===================================================================== ==//从SD卡指定地址读取数据,一次最多512字节unsigned char SdReadBlock(unsigned char *Block, unsigned long address,int len){unsigned int count,i;uchar response;SD_CS=0;// while(1)// {SdCommand(0x11,address,0xff);// SD_DO=1;// P0=SdResponse();// P0=0xff;// while(1);while(response!=0xfe && i<200) {response=SdRead();P0=response;i++;} // if(i>=200) Beep=0;// P0=0xf0;// }// Beep=0;for(count=0;count<512;count++) *Block++=SdRead();SdRead();SdRead();//Now read in the DA TA RESPONSE tokenSD_CS=1;SdWrite(0xff);return 1;}void main(){unsigned int mm;unsigned long AddTemp=0x11200;//70144;//SD卡地址第一个数据物理地址初始值70144是通过winhex查看，对于你的SD卡肯定要改//可以用winhex查看，一定要是512整数倍mm=SdInit();//SdReadBlock(DATA,AddTemp,1);delay(10);// Beep=0;if(DATA[0]==0xeb) Beep=0;// 看读的对不对while(1);}。