sd.c

SD卡的读写

#include "config.h"
#include "sd.h"
//----------------------------------------
//SPI initialize
void spi_init(void)
{
	DDRB = 0xB7;    //SI输入，SO，SCK，SS输出
	SPCR = 0x50;  //setup SPI
	SPSR = 0x01;  //setup SPI
}
//----------------------------------------
void Write_Byte_SPI(unsigned char byte)
{
	SPDR = byte;
	while (!SPSR_Bit7);
}
//----------------------------------------
unsigned char Read_Byte_SPI(void)
{
	SPDR = 0xFF;
	while (!SPSR_Bit7);
	return SPDR;
}

unsigned char SD_Buffer[512];
//****************************************************************************
//Send a Command to SD-Card
//Return: the second byte of response register of SD-Card
//****************************************************************************
unsigned char Write_Command_SD(unsigned char cmd,unsigned long arg,unsigned char crc7)
{
	unsigned char tmp;
	unsigned char retry=0;

	//set MMC_Chip_Select to high (SD-Card disable)
	SD_Disable();

	//send 8 Clock Impulse
	Write_Byte_SPI(0xFF);			//for ZZZZZZZZ	state
	//set MMC_Chip_Select to low (SD-Card active)

	SD_Enable();

	//send 6 Byte Command to SD-Card
	Write_Byte_SPI(cmd|0x40);   				//送头命令
	Write_Byte_SPI( (arg>>24) & 0xff );
	Write_Byte_SPI( (arg>>16) & 0xff );
	Write_Byte_SPI( (arg>> 8) & 0xff );
	Write_Byte_SPI(  arg&0xff);
	Write_Byte_SPI(crc7);       //仅仅对RESET有效的CRC效验码

	//get 16 bit response
	Read_Byte_SPI(); //read the first byte,ignore it.
	do
	{  //Only last 8 bit is used here.Read it out.
		tmp = Read_Byte_SPI();
		retry++;
	}
	while((tmp==0xff)&&(retry<100));
	return(tmp);
}

//****************************************************************************
//Routine for Init SD card(SPI-MODE)
//****************************************************************************
unsigned char SD_Init(void)
{
	unsigned char retry,temp;
	unsigned char i;

	spi_init();
	//MMC_Port_Init(); //Init SPI port
	for(i=0;i<200;i++) //Wait SD ready...
	{
		NOP();
	}
	
	SD_Enable();
	for (i=0;i<0xff;i++)
	{
		Write_Byte_SPI(0xFF); //send 74 clock at least!!!
	}

	//Send Command CMD0 to SD Card
	retry=0;
	do
	{ //retry 200 times to send CMD0 command
		temp=Write_Command_SD(00,00,0x95);
		retry++;
		if(retry==200)
		{
			SD_Disable();  //set SD_Chip_Select to high
			return(INIT_CMD0_ERROR);//CMD0 Error!
		}
	}
	while(temp!=1);
	delay_ms(30);

	//Send Command CMD1 to SD-Card
	retry=0;
	do
	{
		temp=Write_Command_SD(0x01,0x00,0xFF);
		retry++;
		if(retry==100)
		{
			SD_Disable();  //set SD_Chip_Select to high
			return(INIT_CMD1_ERROR);//CMD1 Error!
		}
	}
	while(temp!=0);

	Write_Command_SD(16,512,0xFF);			//sent com16 to sd to set a block len

	SD_Disable();  //set SD_Chip_Select to high

	return(0); //All commands have been taken.
}

unsigned char SD_Read_Block(unsigned long addr)
{
	unsigned char tmp;
	unsigned int i;
	addr<<=9;
	tmp=Write_Command_SD(17,addr,0xff);
	while (Read_Byte_SPI()!= 0xfe){	WDR();	}
	for(i=0;i<512;i++)
	{
		SD_Buffer[i]=Read_Byte_SPI();
	}
	SD_Disable();
	return(tmp);
}