sd._c

AVR单片机系统开发经典实例部分源程序

//---------------------------- SD卡驱动程序 ----------------------------
//
//简化版SD卡驱动程序
//整理日期：2009.7.8
//
//------------------------------------------------------------------------

#include"sd.h"
#include"Usart.h"


//---------------------------------
//
//     SD卡接口初始化函数 
//
//---------------------------------
void SD_Port_Init(void)
{
 SD_CS_DDR |= 1<<SD_CS_BIT;
 SD_CS_PORT |= 1<<SD_CS_BIT;
}



//---------------------------------
//
// SD卡写寄存器函数 
// arg：命令
// cmd：命令号
//
//---------------------------------
uint8 SD_SendCommand(uint8 cmd, uint32 arg)
{
	uint8 r1=1;
	uint8 retry=0;
	

	SPI_SrByte(0xff);
	SPI_CS_Assert;
	while(r1--);
	
	SPI_SrByte((cmd & 0x3f) | 0x40);	/* send command */
	
	SPI_SrByte(arg>>24);
	SPI_SrByte(arg>>16);
	SPI_SrByte(arg>>8);
	SPI_SrByte(arg);
	
	SPI_SrByte(0x95);
	
	SPI_SrByte(0xff);
	while((r1 = SPI_SrByte(0xff)) == 0xff)	/* wait response */
		if(retry++ > 0xfe) break;				/* time out error */

	SPI_CS_Deassert;
	SPI_SrByte(0xff);				// extra 8 CLK

	return r1;								/* return state */
}


//---------------------------------
//
//        SD卡初始化函数 
//
//---------------------------------
uint8 SD_Init(void)
{
    
	uint8 i;
	uint8 retry = 0;
	uint8 r1 = 0;
	
	SD_Port_Init();
	
	SPI_CS_Assert;
	delay_ms(1);
	SPI_CS_Deassert;
	delay_ms(1);
	
	
	SPI_Low();	
	
	do
	{
		for(i=0;i<10;i++) SPI_SrByte(0xff);
		r1 = SD_SendCommand(0, 0);//发idle命令	//send idle command
		retry++;
		if(retry>0xfe) return 1;//超时退出		//time out
	} while(r1 != 0x01);	


	retry = 0;
	do
	{
		r1 = SD_SendCommand(1, 0);//发active命令	//send active command
		retry++;
		if(retry>0xfe) return 1;//超时退出		//time out
	} while(r1);
	
	SPI_High();		/* Use High Speed SPI*/
	
	r1 = SD_SendCommand(59, 0);//关crc		//disable CRC

	r1 = SD_SendCommand(16, 512);//设扇区大小512	//set sector size to 512
	return 0;//正常返回		//normal return
}



//---------------------------------------------
//
// SD卡扇区读取函数 
// sector：扇区号
// buffer：数据缓存
//
//---------------------------------------------
uint8 SD_ReadBlock(uint32 sector, uint8* buffer)
{
	uint8 r1;
	uint16 i;
	uint16 retry=0;

	SPI_High();		/* Use High Speed SPI*/

	r1 = SD_SendCommand(17, sector<<9);//读命令	//read command
	
	if(r1 != 0x00)
		return r1;

	SPI_CS_Assert;
	//等数据的开始	//wait to start recieve data
	while(SPI_SrByte(0xff) != 0xfe)
	 if(retry++ > 0xfffe)
		 {SPI_CS_Deassert;return 1;}

	for(i=0; i<512; i++)//读512个数据	//read 512 bytes
	{
		*buffer++ = SPI_SrByte(0xff);
	}

	SPI_SrByte(0xff);//伪crc    //dummy crc
	SPI_SrByte(0xff);
	
	SPI_CS_Deassert;
	SPI_SrByte(0xff);// extra 8 CLK
	 

	return 0;
}


//---------------------------------------------
//
// SD卡扇区写入函数 
// sector：扇区号
// buffer：数据缓存
//
//---------------------------------------------
uint8 SD_WriteSingleBlock(uint32 sector, uint8* buffer)
{
	uint8 r1;
	uint16 i;
	uint16 retry=0;
	
	//SPI_High();		/* Use High Speed SPI*/

	r1 = SD_SendCommand(24, sector<<9);//写命令	//send command
	if(r1 != 0x00)
		return r1;

	SPI_CS_Assert;
	
	SPI_SrByte(0xff);
	SPI_SrByte(0xff);
	SPI_SrByte(0xff);

	SPI_SrByte(0xfe);//发开始符			//send start byte "token"
	
	for(i=0; i<512; i++)//送512字节数据		//send 512 bytes data
	{
		SPI_SrByte(buffer[i]);
	}
	
	SPI_SrByte(0xff);			//dummy crc
	SPI_SrByte(0xff);
	
	r1 = SPI_SrByte(0xff);
	
	if( (r1&0x1f) != 0x05)//等待是否成功	//judge if it successful
	{
		SPI_CS_Deassert;
		return r1;
	}
	//等待操作完		//wait no busy
	while(!SPI_SrByte(0xff))if(retry++ > 0xfffe){SPI_CS_Deassert;return 1;}

	SPI_CS_Deassert;
	//SPI_SrByte(0xff);// extra 8 CLK

	return 0;
}