这是我自己搜改的　　　希望大家多提建议　　　

#include "HAL.H"


//============================================================
//往SD卡定一字节
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
unsigned char SdRead()
{
unsigned char n,i;
for(i=8;i;i--)
  {
   SD_CLK=0;
   SD_CLK=1;
   n<<=1;
   if(SD_DO) n|=1;   

  }
return n;
}
//================================================================
//读SD卡响应
unsigned char SdResponse()
{
  unsigned char i=0,response;
  
  while(i<=8)
  {
    response=SdRead();
    if(response==0x00)
      break;
    if(response==0x01)
      break;
    i++;
  }
  return response;
}  
//================================================================
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(CRC);
}
//================================================================
unsigned char SdInit(void)
{
  int delay=0, trials=0;
  unsigned char i;
  unsigned char response=0x01;    //你这里定义response=0x01是不是多余啊

  SD_CS=1;
  for(i=0;i<=9;i++)
    SdWrite(0xff);
  SD_CS=0;
  
  //Send Command 0 to put MMC in SPI mode
  SdCommand(0x00,0,0x95);              //send CMD0

  
  response=SdResponse();
  
  if(response!=0x01)
   {
    return 0;
   }
  
  while(response==0x01)
  {
    SD_CS=1;
    SdWrite(0xff);
    SD_CS=0;
    SdCommand(0x01,0x00ffc000,0xff);    // send CMD1 这里一定要写0x00ffc000吗？
    response=SdResponse();
  }
    
  SD_CS=1;
  SdWrite(0xff);
  return 1;  
}
//================================================================
unsigned char SdWriteBlock(unsigned char *Block, unsigned long address)
{
  unsigned char  count;
  unsigned char dataResp;
  //Block size is 512 bytes exactly
  //First Lower SS
  
  SD_CS=0;
  //Then send write command
  SdCommand(0x18,address,0xff);  //CMD24 WRITE_BLOCK
  
  if(SdResponse()==00)
  {
    SdWrite(0xff);
    SdWrite(0xff);
    SdWrite(0xff);
    //command was a success - now send data
    //start with DATA TOKEN = 0xFE
    SdWrite(0xfe);
    //now send data
    for(count=0;count<128;count++)
    {
      SdWrite(*Block++);
      SdWrite(*Block++);
      SdWrite(*Block++);
      SdWrite(*Block++);
    }
    //data block sent - now send checksum
    SdWrite(0xff);
    SdWrite(0xff);
    //Now read in the DATA RESPONSE token
    dataResp=SdRead();
    //Following the DATA RESPONSE token
    //are a number of BUSY bytes
    //a zero byte indicates the MMC is busy

    while(SdRead()==0);

    dataResp=dataResp&0x0f;    //mask the high byte of the DATA RESPONSE token
    SD_CS=1;
    SdWrite(0xff);
    if(dataResp==0x0b)
      {
      //printf("DATA WAS NOT ACCEPTED BY CARD -- CRC ERROR\n");
      return 0;
      }
    if(dataResp==0x05)
      return 1;
      
    //printf("Invalid data Response token.\n");
    return 0;
}
  //printf("Command 0x18 (Write) was not received by the MMC.\n");
  return 0;
}
//=======================================================================
unsigned char SdReadBlock(unsigned char *Block, unsigned long address)
{
   unsigned char count;
  //Block size is 512 bytes exactly
  //First Lower SS
  
//  printf("MMC_read_block\n");
  
  SD_CS=0;
  //Then send read command
  SdCommand(0x11,address,0xff);       //send CMD17 READ_SINGLE_BLOCK
  
  if(SdResponse()==00)
  {
    //command was a success - now send data
    //start with DATA TOKEN = 0xFE
    while(SdRead()!=0xfe);

    for(count=0;count<128;count++)
    {
      *Block++=SdRead();
      *Block++=SdRead();
      *Block++=SdRead();
      *Block++=SdRead();
    }
    //data block sent - now send checksum
    SdRead();
    SdRead();          //send two CRC bytes to host
    //Now read in the DATA RESPONSE token
    SD_CS=1;
    SdRead();
    return 1;
}
//  printf("Command 0x11 (Read) was not received by the MMC.\n");
  return 0;
}

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