STC52单片机的SD卡底层驱动——SPI

最近在做SD卡以及单片机上的FAT32文件系统，这个是我参考别人的源程序以后写出来的自己的SD卡驱动，如有不完整的地方，还望大家不吝指教。

定义声明：

#ifndef _SD_H_
#define _SD_H_

#include

sbit SD_CS=P2^7;//SD卡片选信号
sbit SD_SI=P2^6;//SD卡数据输入
sbit SD_SCL=P2^5;//SD卡时钟信号
sbit SD_SO=P2^4;//SD卡数据输出

#define DELAY_TIME 100//SD卡的复位与初始化时SPI延时
#define TRY_TIME 200//SD卡写入命令以后，读取SD卡的回应次数

#define INIT_CMD0_ERROR0x01//CMD0错误
#define INIT_CMD1_ERROR0x02//CMD1错误
#define WRITE_BLOCK_ERROR 0x03//写块错误
#define READ_BLOCK_ERROR0x04//读块错误

unsigned char SD_Reset();
unsigned char SD_Init();
unsigned char SD_Write_Sector(unsigned long addr,unsigned char *buffer);
unsigned char SD_Read_Sector(unsigned long addr,unsigned char *buffer);

#endif

代码实现：

#include"SD.h"
#include"myfun.h"

unsigned char Is_init;

unsigned char bdata _dat;
sbit _dat7 = _dat^7;
sbit _dat6 = _dat^6;
sbit _dat5 = _dat^5;
sbit _dat4 = _dat^4;
sbit _dat3 = _dat^3;
sbit _dat2 = _dat^2;
sbit _dat1 = _dat^1;
sbit _dat0 = _dat^0;

void SD_spi_write(unsigned char x)
{
_dat=x;

SD_SI = _dat7;
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL=1;
if(Is_init) Delay20us(DELAY_TIME);

SD_SI = _dat6;
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL=1;
if(Is_init) Delay20us(DELAY_TIME);

SD_SI = _dat5;
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL=1;
if(Is_init) Delay20us(DELAY_TIME);

SD_SI = _dat4;
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL=1;
if(Is_init) Delay20us(DELAY_TIME);

SD_SI = _dat3;
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL=1;
if(Is_init) Delay20us(DELAY_TIME);

SD_SI = _dat2;
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL=1;
if(Is_init) Delay20us(DELAY_TIME);

SD_SI = _dat1;
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL=1;
if(Is_init) Delay20us(DELAY_TIME);

SD_SI = _dat0;
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL=1;
if(Is_init) Delay20us(DELAY_TIME);

}

unsigned char SD_spi_read()
{
SD_SO = 1;

SD_SCL = 1;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
_dat7 = SD_SO;

SD_SCL = 1;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
_dat6 = SD_SO;

SD_SCL = 1;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
_dat5 = SD_SO;

SD_SCL = 1;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
_dat4 = SD_SO;

SD_SCL = 1;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
_dat3 = SD_SO;

SD_SCL = 1;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
_dat2 = SD_SO;

SD_SCL = 1;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
_dat1 = SD_SO;

SD_SCL = 1;
if(Is_init) Delay20us(DELAY_TIME);
SD_SCL = 0;
if(Is_init) Delay20us(DELAY_TIME);
_dat0 = SD_SO;

return(_dat);
}

unsigned char SD_Write_Cmd(unsigned char *pcmd)
{
unsigned char temp,time=0;

SD_CS=1;
SD_spi_write(0xff);//提高程序的兼容性
SD_CS=0;

SD_spi_write(pcmd[0]);
SD_spi_write(pcmd[1]);
SD_spi_write(pcmd[2]);
SD_spi_write(pcmd[3]);
SD_spi_write(pcmd[4]);
SD_spi_write(pcmd[5]);
do
{
temp = SD_spi_read();
time++;
}
while((temp==0xff)&&(time return(temp);
}

unsigned char SD_Reset()
{
unsigned char time,temp,i;
unsigned char pcmd[] = {0x40,0x00,0x00,0x00,0x00,0x95};

Is_init = 1;

SD_CS = 1;//关闭片选
for(i=0;i<0x0f;i++){
SD_spi_write(0xff); //补充120个时钟，唤醒SPI
}
SD_CS = 0;//打开片选
time=0;
do{
temp=SD_Write_Cmd(pcmd);//写入CMD0
time++;
if(time==TRY_TIME){
SD_CS = 1; //关闭片选
return(INIT_CMD0_ERROR); //CMD0 写入失败
}
}while(temp!=0x01);

SD_CS = 1;//关闭片选

SD_spi_write(0xff);//补充8个时钟，提高兼容性

return 0 ;//返回0，复位操作成功
}

unsigned char SD_Init()
{
unsigned char time,temp;
unsigned char pcmd[] = {0x41,0x00,0x00,0x00,0x00,0xff};
SD_CS = 0; //打开片选

time = 0;
do{
temp = SD_Write_Cmd(pcmd);
time++;
if(time==TRY_TIME){ //CMD1写入失败
SD_CS=1;
return(INIT_CMD1_ERROR);
}
}while(temp!=0);

Is_init = 0; //讲Is_init设置为0，提高SPI速度
SD_CS = 1;//关闭片选
SD_spi_write(0xff);//补充8个时钟
return(0);
}

unsigned char SD_Write_Sector(unsigned long addr,unsigned char *buffer)
{
unsigned char temp,time;
unsigned int i;
unsigned char pcmd[]={0x58,0x00,0x00,0x00,0x00,0xff};

addr<<=9;
pcmd[1] = ((addr&0xff000000)>>24);
pcmd[2] = ((addr&0x00ff0000)>>16);
pcmd[3] = ((addr&0x0000ff00)>>8);

SD_CS = 0;
time = 0;

do{
temp=SD_Write_Cmd(pcmd);//写入CMD0
time++;
if(time == TRY_TIME)
{
SD_CS = 1;//关闭片选
return(temp); //写入失败
}
}while(temp!=0);

for(i=0;i<100;i++)//插入若干个字节的时钟，保持稳定性
{
SD_spi_write(0xff);
}

SD_spi_write(0xfe);//写入0xfe，后面就是要写入的数据

for(i=0;i<512;i++)
{
SD_spi_write(buffer[i]);
}

SD_spi_write(0xff);//两个字节的CRC校验码
SD_spi_write(0xff);

temp = SD_spi_read();//读取返回值
if((temp&0x1f)!=0x05){
SD_CS = 1;
return(WRITE_BLOCK_ERROR);//写块数据失败
}
while(SD_spi_read()!=0xff);//SD卡忙状态，等待

SD_CS = 1;

SD_spi_write(0xff);//补充8个时钟
return(0);

}

unsigned char SD_Read_Sector(unsigned long addr,unsigned char *buffer)
{
unsigned int j;
unsigned char time,temp;
unsigned char pcmd[]={0x51,0x00,0x00,0x00,0x00,0xff}; //CMD17的字节序列

addr<<=9; //addr=addr*512将块地址（扇区地址）转为字节地址

pcmd[1]=((addr&0xff000000)>>24);//将字节地址写入到CMD17字节序列中
pcmd[2]=((addr&0x00FF0000)>>16);
pcmd[3]=((addr&0x0000FF00)>>8);

SD_CS=0;//打开片选

time=0;
do{
temp = SD_Write_Cmd(pcmd);
time++;
if(time==TRY_TIME){
return(READ_BLOCK_ERROR);
}
}while(temp!=0);

while(SD_spi_read()!=0xfe);//读到0xfe，说明后面是512字节的数据

for(j=0;j<512;j++)
{
buffer[j]=SD_spi_read();
}

SD_spi_read();//读取两个字节的CRC校验码
SD_spi_read();

SD_CS=1;

SD_spi_write(0xff);//补充8个时钟

return 0;

}