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          EEPW首頁 
	 > 嵌入式系統(tǒng) > 設計應用 > 51單片機讀寫SD卡程序
          
    
          

          

          


	
	
	

          
	
          
		
          
			
          51單片機讀寫SD卡程序
          
						
          
				作者：
				時間：2016-11-29
				來源：網(wǎng)絡
				
				
				
				
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          //================================================================
          //往SD卡指定地址寫數(shù)據(jù),一次最多512字節(jié)
          //unsigned char SdWriteBlock(unsigned char *Block, unsigned long address,int len)
          unsigned char SdWriteBlock(unsigned long address,int len)
          {
          unsigned int count;
          unsigned char dataResp;
          //Block size is 512 bytes exactly
          //First Lower SS
          SD_CS=0;
          //Then send write command
          SdCommand(0x18,address,0xff);
          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;countfor(count=0;count//for(count=0;countfor(;count<512;count++) SdWrite(0);
          //data block sent - now send checksum
          SdWrite(0xff); //兩字節(jié)CRC校驗, 為0XFFFF 表示不考慮CRC
          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");
          return 0;
          }
          if(dataResp==0x05)
          return 1;
          //printf("Invalid data Response token.");
          return 0;
          }
          //printf("Command 0x18 (Write) was not received by the MMC.");
          return 0;
          }
          //=======================================================================
          //從SD卡指定地址讀取數(shù)據(jù),一次最多512字節(jié)
          unsigned char SdReadBlock(unsigned char *Block, unsigned long address,int len)
          {
          unsigned int count;
          //Block size is 512 bytes exactly
          //First Lower SS
          //printf("MMC_read_block");
          SD_CS=0;
          //Then send write command
          SdCommand(0x11,address,0xff);
          if(SdResponse()==00)
          {
          //command was a success - now send data
          //start with DATA TOKEN = 0xFE
          while(SdRead()!=0xfe);
          for(count=0;countfor(;count<512;count++) SdRead();
          //data block sent - now send checksum
          SdRead();
          SdRead();
          //Now read in the DATA RESPONSE token
          SD_CS=1;
          SdRead();
          return 1;
          }
          //printf("Command 0x11 (Read) was not received by the MMC.");
          return 0;
          }

          void initbaud(void)
          {
          TMOD=0X20;
          TH1=0XFD;
          TL1=0XFD;
          PCON=0X00;
          TR1=1;
          SCON=0X50;//8位波特可變
          //SCON=0X52;//8位波特可變 TI開中斷
          }
          //============================================================
          //主程序 
          main()
          {
          unsigned int i;
          unsigned long AddTemp=331264;//SD卡地址第一個數(shù)據(jù)物理地址初始值，可以用winhex查看，這里是641物理扇區(qū)，512x641=328192，根據(jù)實際SD卡內(nèi)容更改
          delayms(5);
          SdInit(); //SD卡初始化
          while(1)
          {
          SdWriteBlock(AddTemp,512);
          delayms(1000);
          AddTemp=331264;
          SdReadBlock(DATA,AddTemp,512);//每次讀出512字節(jié)放到緩沖區(qū)
          initbaud();
          for(i=0;i<512;i++)
          {
          SBUF=DATA[i];
          while(!TI);
          TI=0;
          delayms(1);
          }
          while(KEY); //等待按鍵按下繼續(xù)執(zhí)行

          }
          }
          可以在串口中看到SD卡中被寫入的數(shù)據(jù)，程序在MCU-51/AVR開發(fā)板進行了實驗。具體介紹可訪問：
          http://item.taobao.com/item.htm?spm=0.0.0.50.xZjZ87&id=21441052281，http://item.taobao.com/item.htm?spm=1103*oQM.3-5SusJ.h-2Yh1mq&id=14049701171& 這是兩款功能強大的51、AVR開發(fā)板，對初學者和研發(fā)人員都是不錯的選擇，下一節(jié)給大家講下結(jié)合SD卡的TFT真彩屏的相關讀寫！



          
				
            
                
			
							
          
                
			            
          
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