单片机读写SD卡教程.doc
《单片机读写SD卡教程.doc》由会员分享,可在线阅读,更多相关《单片机读写SD卡教程.doc(8页珍藏版)》请在冰点文库上搜索。
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
#defineucharunsignedchar
#defineuintunsignedint
//=============================================================
//定义SD卡需要的4根信号线
sbitSD_CLK=P1^1;
sbitSD_DI=P1^2;
sbitSD_DO=P1^0;
sbitSD_CS=P1^3;
sbitBeep=P2^0;//用来调程序标志
//===========================================================
//===========================================================
//定义512字节缓冲区,,89C52直接定义成unsignedcharDATA[80];,太大了RAM不够
unsignedcharxdataDATA[512];
voiddelay(unsignedintz)
{
unsignedintx,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
voidSdWrite(unsignedcharn)
{
unsignedchari;
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
unsignedcharSdRead()
{
unsignedcharn,i;
for(i=8;i;i--)
{
SD_CLK=1;
SD_CLK=0;
n<<=1;
if(SD_DO)n|=1;
}
returnn;
}
//============================================================
//检测SD卡的响应
unsignedcharSdResponse()
{
uchari=0,response=0;
while(i<=8)
{
response=SdRead();
if(response==0x00)
break;
if(response==0x01)
break;
i++;
}
returnresponse;
}
//================================================================
//发命令到SD卡
voidSdCommand(unsignedcharcommand,unsignedlongargument,unsignedcharCRC)
{
SdWrite(command|0x40);
/*SdWrite(((unsignedchar*)&argument)[0]);
SdWrite(((unsignedchar*)&argument)[1]);
SdWrite(((unsignedchar*)&argument)[2]);
SdWrite(((unsignedchar*)&argument)[3]);*/
SdWrite(argument>>24);
SdWrite(argument>>16);
SdWrite(argument>>8);
SdWrite(argument);
SdWrite(CRC);
}
//================================================================
//初始化SD卡
unsignedcharSdInit(void)
{
unsignedchari;
unsignedcharresponse=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)
{
return0;
}
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SPI
response=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SPI
SD_CS=1;
SdWrite(0xff);
SD_CS=0;
// Beep=0;
return1;
}
}
//================================================================
//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
unsignedcharSdWriteBlock(unsignedchar*Block,unsignedlongaddress,intlen)
{
unsignedintcount;
unsignedchardataResp;
SD_CS=0;
SdCommand(0x18,address,0xff);
if(SdResponse()==00)
{
SdWrite(0xff);
SdWrite(0xff);
SdWrite(0xff);
//commandwasasuccess-nowsenddata
//startwithDATATOKEN=0xFE
SdWrite(0xfe);
//nowsenddata
for(count=0;countfor(;count<512;count++)SdWrite(0);
//datablocksent-nowsendchecksum
SdWrite(0xff);//两字节CRC校验,为0XFFFF表示不考虑CRC
SdWrite(0xff);
//NowreadintheDATARESPONSEtoken
dataResp=SdRead();
while(SdRead()==0);
dataResp=dataResp&0x0f;//maskthehighbyteoftheDATARESPONSEtoken
SD_CS=1;
SdWrite(0xff);
if(dataResp==0x0b)
{
return0;
}
if(dataResp==0x05)return1;
return0;
}
//printf("Command0x18(Write)wasnotreceivedbytheSD.\n");
return0;
}
//=======================================================================
//从SD卡指定地址读取数据,一次最多512字节
unsignedcharSdReadBlock(unsignedchar*Block,unsignedlongaddress,intlen)
{
unsignedintcount,i;
ucharresponse;
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();
//NowreadintheDATARESPONSEtoken
SD_CS=1;
SdWrite(0xff);
return1;
}
voidmain()
{
unsignedintmm;
unsignedlongAddTemp=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);
}