AVR的SD卡接口程序

/************************************************************/
/*SDCodeforM32L*/

/*Bypasyong*/
/*2006-4*/
/*BaseICC6.31A*/
/************************************************************/
#include
#include
#include"1011.h"
#defineucharunsignedchar
#defineuintunsignedint
#defineMMC_CS_PINBIT(4)//PORTB.4
#defineMMC_PORTPORTB

ucharreading=0,a=0,pointer=0;
voidsd_port_init()
{
MMC_PORT|=MMC_CS_PIN;
}
ucharBUFFER[512];//扇区缓冲区
uinti=0;
voiddelay_nus(uintn)
{
unsignedcharb;
for(b=1;b;
}
//****************************************************************************
//SendaCommandtoMMC/SD-Card
//Return:thesecondbyteofresponseregisterofMMC/SD-Card
//****************************************************************************
ucharSD_Write_Command(ucharcmd,unsignedlongarg)
{
uchartmp;
ucharretry=0;

//MMC_PORT|=MMC_CS_PIN;//SD卡关闭
//send8CLOCkImpulse
Write_Byte_SPI(0xFF);

//setMMC_Chip_Selecttolow(MMC/SD-Cardactive)
MMC_PORT&=~MMC_CS_PIN;//SD卡使能

Write_Byte_SPI(cmd|0x40);//送头命令
Write_Byte_SPI(arg>>24);
Write_Byte_SPI(arg>>16);//send6ByteCommandtoMMC/SD-Card
Write_Byte_SPI(arg>>8);
Write_Byte_SPI(arg&0xff);
Write_Byte_SPI(0x95);//仅仅对RESET有效的CRC效验码

//get8bitresponse
//Read_Byte_MMC();//readthefirstbyte,ignoreit.
do
{//Onlylast8bitisusedhere.Readitout.
tmp=Read_Byte_SPI();
retry++;
}
while((tmp==0xff)&&(retry<100));//当没有收到有效的命令的时候

if(reading==0)
MMC_PORT|=MMC_CS_PIN;//MMC_CS_PIN=1;
elseMMC_PORT&=~MMC_CS_PIN;//MMC_CS_PIN=0;
return(tmp);
}
//****************************************************************************
//SD卡初始化(SPI-MODE)
//****************************************************************************
ucharSD_Init(void)
{
ucharretry,temp;
uchari;
MMC_PORT&=~MMC_CS_PIN;//SD卡使能

delay_nus(250);//WaitMMC/SDready...
for(i=0;i<0x0f;i++)
{
Write_Byte_SPI(0xff);//send74clockatleast!!!
}
//SendCommandCMD0toMMC/SDCard
retry=0;

do
{//retry200timestosendCMD0command
temp=SD_Write_Command(0,0);
retry++;
if(retry==100)
{
;//CMD0Error!
}
}
while(temp!=1);

//SendCommandCMD1toMMC/SD-Card
retry=0;
do
{//retry100timestosendCMD1command
temp=SD_Write_Command(1,0);
retry++;
if(retry==100)
{
;
}
}
while(temp!=0);
retry=0;
SD_Write_Command(16,512);//设置一次读写BLOCK的长度为512个字节

MMC_PORT|=MMC_CS_PIN;//MMC_CS_PIN=1;//setMMC_Chip_Selecttohigh
return(0);//Allcommandshavebeentaken.
}
//****************************************************************************
//从SD卡读一个扇区Return0ifnoError.
//****************************************************************************
ucharSD_Read_Block(unsignedlongaddress)
{
uchartemp=0;uinti=0;
reading=1;
temp=SD_Write_Command(17,address);//读出RESPONSE
while(Read_Byte_SPI()!=0xfe)
{;}//直到读取到了数据的开始头0XFE,才继续
for(i=0;i<512;i++)
{
BUFFER[i]=Read_Byte_SPI();
}
Read_Byte_SPI();//CRC-Byte
Read_Byte_SPI();//CRC-Byte
reading=0;
MMC_PORT|=MMC_CS_PIN;//关闭SD卡
return(temp);
}