单片机读写SD卡教程.doc

点这郑重声明：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 #define uchar unsigned char#define uint unsigned int/=/定义SD卡需要的4根信号线sbit SD_CLK = P11;sbit SD_DI = P12;sbit SD_DO = P10;sbit SD_CS = P13;sbit Beep=P20;/用来调程序标志/=/=/定义512字节缓冲区，89C52直接定义成unsigned char DATA80;，太大了RAM不够unsigned char xdata DATA512;void delay(unsigned int z)unsigned int x,y;for(x=z;x0;x-);for(y=110;y0;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(i24);SdWrite(argument16);SdWrite(argument8);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;i250;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;countlen;count+) SdWrite(*Block+);for(;count512;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 DATA 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) Beep=0;/P0=0xf0;/Beep=0;for(count=0;count512;count+) *Block+=SdRead(); SdRead();SdRead();/Now read in the DATA 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