SD.rar_sd writer_sd卡读写

SD卡读写子程序 作者：不详 来源：本站整理 发布时间：2007-1-8 12:51:06 发布人：admin 减小字体 增大字体 硬件平台：atmega8L最小系统 硬spi（sd卡的初始化采用了io口模拟时序，因为在实验中发现要使用较低的速率才能稳定的初始化） 软件开发平台：ICC-AVR version 6.31a 硬件配置：atmega8L 内部8m时钟 sandisk 128m sd卡 几个基本的子程序及其介绍： 1.io口模拟spi，实现数据发送，在初始化时使用 void iodatatransfer(unsigned char iodata) { unsigned char num,b; num=0x80; for (b=0;b<0x08;b++) { WDR();//feed the dog //SD_Write|=(1<<SPI_Clock);//sck=1 SD_Write&=~(1<<SPI_Clock);//sck=0 if(iodata&num) SD_Write|=(1<<SPI_DO);//do=1 else SD_Write&=~(1<<SPI_DO);//do=0 delay_4ms();//4ms WDR();//feed the dog //SD_Write&=~(1<<SPI_Clock);//sck=0 SD_Write|=(1<<SPI_Clock);//sck=1 delay_4ms();//4ms if(num>0x01) num=num>>1; } } 2.io口模拟spi，实现数据读取，在初始化时使用 unsigned char iodataread(void) { unsigned char data,temp,b; data=0; temp=0; for (b=0;b<0x08;b++) { WDR();//feed the dog SD_Write&=~(1<<SPI_Clock);//sck=0 delay_4ms();//4ms WDR();//feed the dog SD_Write|=(1<<SPI_Clock);//sck=1 temp=SD_READ; temp&=0x10;//to maintain the pb.4 bit(data_in) WDR();//feed the dog if(temp) { data|=0x01; } if(b<7) { data=data<<1;// } delay_4ms();//4ms WDR();//feed the dog } return data; } 3.io口模拟spi，实现指令发送及读响应，在初始化时使用 unsigned char iocmd(unsigned char *cmd) { unsigned temp,a,timeout; temp=0xff; timeout=0; // Raise chip select -----/ss=1 SD_Disable(); WDR();//feed the dog // Send an 8 bit pulse iodatatransfer(0xff); WDR();//feed the dog // Lower chip select SD_Enable(); for(a=0;a<6;a++) { iodatatransfer(*cmd++); WDR(); //transfer cmd in io_mode } while(temp==0xff)// { WDR();//feed the dog temp=iodataread(); if(timeout++>100) { break; } } WDR();//feed the dog return(temp);//the respone of the byte_write_operation } 4.硬spi读数据 unsigned char Read_Byte_SD(void) { char Byte; //SD_Enable(); SPDR=0xff; while(!(SPSR&(1<<SPIF)));// Byte=SPDR; return(Byte); } 5.硬spi写数据 void Write_Byte_SD(char Byte) { //SD_Enable(); SPDR=Byte; while(!(SPSR&(1<<SPIF))); } 6.硬spi写指令及读响应 unsigned char Write_Command_SD(char *CMD) { unsigned char a; unsigned char tmp=0xff; unsigned char Timeout=0; // Raise chip select -----/ss=1 SD_Disable(); // Send an 8 bit pulse Write_Byte_SD(0xFF); // Lower chip select SD_Enable(); //Send the 6 byte command for(a=0;a<0x06;a++) { Write_Byte_SD(*CMD++); } //Wait for the response while(tmp==0xff)// { tmp=Read_Byte_SD(); if(Timeout++>100) { break; } } //for some reason we need to delay here //delay_1ms(); return(tmp);//the respone of the byte_write_operation } 7.初始化 unsigned char SDInit(void) { unsigned char a,b,retry,erroetoken; unsigned char CMD[]={0x40,0x00,0x00,0x00,0x00,0x95};//cmd0 // Set certain pins to inputs and others to outputs // Only SPI_DI (data in) is an input //SD_Direction_REG==ddrb SD_Direction_REG&=~(1<<SPI_DI); SD_Direction_REG|=(1<<SPI_Clock); SD_Direction_REG|=(1<<SPI_DO); SD_Direction_REG|=(1<<SD_Chip_Select); //SD_Direction_REG|=(1<<SPI_SS); SD_Disable(); //We need to wait for the SD_Direction_REG to be ready for(a=0;a<200;a++) { WDR();//feed the dog nop(); nop(); }; delay_1ms(); SD_Disable();// iodatatransfer(0xff); WDR();//feed the dog //return 0;/////////// retry=0; SD_Enable(); while((erroetoken=iocmd(CMD))!=0x01)// { WDR(); //serial(erroetoken); if(retry++>200) { //fail and return return 1; } } //return 0;/////////// //Send the 2nd command retry=0; CMD[0]=0x41; CMD[5]=0xFF; while(erroetoken=iocmd(CMD)!=0x00) { WDR(); if (retry++>200) { return 2; } } //Set the SPI bus to full speed SPCR=0x50; SPSR|=0x01; //Raise Chip Select SD_Disable(); return 0; } 8.设置每次读的字节数 char SD_set_length(unsigned int length) { unsigned char retry; //Command to set the block length; char CMD[]={0x50,0x00,0x00,0x00,0x00,0xFF}; //cmd16 CMD[3]=((length&0xFF00)>>8);// CMD[4]= (length&0x00FF); while(Write_Command_SD(CMD)!=0)// { WDR(); if (retry++>200) { return 1; } } SD_Disable(); return 0; } 9.write 512 bytes to a given sector from a Byte_byte_long Buffer unsigned char SD_write_sector(unsigned long addr,unsigned char *Buffer,unsigned int Bytes) { unsigned int a; unsigned char retry,temp; //Command to read a block; char CMD[]={0x58,0x00,0x00,0x00,0x00,0xFF};//cmd24 CMD[1]=((addr&0xFF000000)>>24); CMD[2]=((addr&0x00FF0000)>>16); CMD[3]=((addr&0x0000FF00)>>8); CMD[4]=(addr&0x000000FF); //Send the write command while(Write_Command_SD(CMD)!=0) { if (retry++>50) { return 1; } } //Send the start byte Write_Byte_SD(0xfe); //Read off all the bytes in the block for(a=0;a<Bytes;++a) { Write_Byte_SD(*Buffer++); } while((temp=Read_Byte_SD())&0x10); //serial(temp);//according to p101 of datasheet if((temp&0x0f)!=0x05) return 2; //Read CRC byte while(SD_READ&0x10);//detect if data_in pb.4 is still busy(high) // Set SD_Chip_Select to high SD_Disable(); //SEI(); //re-enable interrupts return 0; } unsigned char SD_read_sector(unsigned long addr,unsigned char *Buffer,unsigned int Bytes) { unsigned int a; unsigned char retry; //Command to read a block; char CMD[]={0x51,0x00,0x00,0x00,0x00,0xFF};//cmd17 //CLI(); //disable all interrupts //addr = addr << 9; //addr = addr * 512 CMD[1]=((addr&0xFF000000)>>24); CMD[2]=((addr&0x00FF0000)>>16); CMD[3]=((addr&0x0000FF00)>>8); CMD[4]=(addr&0x000000FF); //Send the read command while(Write_Command_SD(CMD)!=0) { WDR();//feed the dog if (retry++>200) { return 1; } } //Send the start byte while(Read_Byte_SD()!=0xfe) { WDR();//feed the dog } //Read off all the bytes in the block for(a=0;a<Bytes;++a) { WDR();//feed the dog *Buffer=Read_Byte_SD(); //serial(*Buffer); Buffer++; } //Read CRC byte Read_Byte_SD(); Read_Byte_SD(); // Set SD_Chip_Select to high SD_Disable(); //SEI(); //re-enable interrupts return 0; } /* //read xx bytes no matter of misalignment!! */ unsigned char read_antimisaliment(unsigned long addr_temp,unsigned char *p_buffer, unsigned int length) { unsigned int _length=0x0000; SD_Enable(); while(SD_read_sector(addr_temp,p_buffer,length)) { SD_Enable();// length-=0x0001;//to find a suuitable length to avoid misalignment _length+=0x0001;// _length+length==xx SD_set_length(length); } /// if(_length==0x0000) { return 0; } /// addr_temp+=length; SD_Enable();// SD_set_length(_length); SD_Enable();// while(SD_read_sector(addr_temp,p_buffer,_length)) { SD_Enable(); } SD_Enable();