sd._c

mp3源码,是自己写的,关于vs1001与CD卡的读取歌曲,和播放.

#include<all.h>
#include<vs1001k.h>
#include<sd.h>
#define SD_INIT_TRY   50
#define SD_IDLE_WAIT_MAX  100 //等待进入IDLE次数
#define SD_CMD_TIMEOUT    100 //读CMD次数
#define TIMEOUT_WRITE  10000   // 8M/8
#define TIMEOUT_READ   400000  // 8M/20

uchar mp3_data[DATA_LENGTH];
uchar response[5];

void sd_wait_nobusy(void)
{
  while(read_single()!=0xff);
  select_vs;
}
void sd_delay(uchar dat)
{ uint n;
  for(n=0;n<dat;n++)
   write_single(0xff);
}   
/****************sd 发命令**********************/
uchar sd_write_command(uchar cmd,uchar response_type,ulong arg,uchar *response)
{ uchar response_length,dat;
  int n;
  select_sd;//选择SD
  write_single(cmd|0x40);
  write_single(arg>>24);
  write_single(arg>>16);
  write_single(arg>>8);
  write_single(arg);
  write_single(0x95);//CRC 对于CMD0有效，SPI忽略
  response_length=0;
  switch(response_type)
  { case R1: 
    case R1B:response_length=1;break;
	case R2: response_length=2;break;
	case R3: response_length=5;break;
	default: break;
  }	
  n=0;
  do                              //等待响应
  { dat=read_single();
    n++;
  }
  while(((dat&0x80)!=0)&&(n<SD_CMD_TIMEOUT));
  if(n>=SD_CMD_TIMEOUT)	//超时
  { select_vs;
    return 0;
  }	
  for(n=response_length-1;n>=0;n--)//取数据
  { response[n]=dat;
    dat=read_single();
  }	
  if(response_type==R1B)//忙等待结束
  { do
    { dat=read_single();}
	while(dat!=0xff);
	write_single(0xff);
  }
  select_vs;//释放SD
  return 1;	  
}

uchar read_block(ulong blockadd,uint length,uchar *mp3_data) 
{ uchar dat;
  ulong n;  
  sd_wait_nobusy();
  if(sd_write_command(CMD16,CMD16_R,length,response)==0)//设置读取数据的长度
    return 0; 
  //blockadd<<=9;//增加512B
  if(sd_write_command(CMD17,CMD17_R,blockadd,response)==0)
    return 0;
  if(response[0]!=0)//出现error
    return 0;
  select_sd;
  n=0;
  do
  { dat=read_single();
    n++;
  }
  while((dat==0xff)&&(n<TIMEOUT_READ));//读出数据的头0xfe	
  for(n=0;n<length;n++)
  { mp3_data[n]=read_single();}
  read_single();//CRC 16bit
  read_single();
  select_vs;
  return 1;
}

void sd_read_block(ulong blockadd,uint length,uchar *mp3_data)//读SD数据
{ while(read_block(blockadd,length,mp3_data)==0);}

uchar do_sd_init(void)//sd初始化
{ uchar n;
  delay(200);
  select_sd;
  sd_delay(100);
  select_vs;
  sd_delay(2);
  if(sd_write_command(CMD0,CMD0_R,0,response)==0)
    return 0;
  n=0;
  do
  { n++;
    if(sd_write_command(CMD55,CMD55_R,0,response)==1)//进入special command
	 { /*getin OCR*/
	  sd_write_command(ACMD41,ACMD41_R,0,response);
	 }
	else
	  n=SD_IDLE_WAIT_MAX;  //no response
	delay(500);//经调试需要加延迟
  }
  while(((response[0]&MSK_IDLE)==MSK_IDLE)&&(n<SD_IDLE_WAIT_MAX));
  if(n>=SD_IDLE_WAIT_MAX)
    return 0;
  if(sd_write_command(CMD58,CMD58_R,0,response)==0)//读取OCR
    return 0;
  if((response[2]&MSK_OCR_33)!=MSK_OCR_33)//电压最低为3.3V
    return 0;
  /*set block length			
  if(sd_write_command(CMD16,CMD16_R,DATA_LENGTH,response)==0)
    return 0;
  */
  return 1;    
}

uchar sd_init(void)
{ uchar n,j;
  j=0;
  for(n=0;(n<SD_INIT_TRY)&&(j!=1);n++)
    j=do_sd_init();
  if(n>=SD_INIT_TRY)//超次数
    return 0;	
  return 1;
}  	  

/****************song***************/