mmc_sd.c

mega8的mp3代码

/*************************************************************/
/*                   SD/MMC操作函数库                        */
/*  环境WinAVR 20060421                                      */
/*  作者：Bozai（章其波）                                    */
/*  E-mail：[e-mail]                                  */
/*  2006年11月26日                                           */
/*************************************************************/





#include <avr/io.h>
#include "MMC_SD.h"


//低速模式
void SPI_Low(void)
{
	SPCR =   _BV(SPE)|_BV(MSTR)|_BV(SPR1)|_BV(SPR0);
	SPSR &= ~_BV(SPI2X);
}

//高速模式
void SPI_High(void)
{
	SPCR =  _BV(SPE)|_BV(MSTR);
	SPSR |= _BV(SPI2X);
}

//端口初始化，模式初始化
void SPI_Init(void)
{
	DDR_INI();
	SPI_Low();
}

//写读一个字节
uint8 SPI_WriteByte(uint8 val)
{
	SPDR = val;
	while(!(SPSR & _BV(SPIF)));
	return SPDR;
}

/*uint8 SPI_ReadByte(void)
{
	SPDR = 0xff;
	while(!(SPSR & _BV(SPIF)));
	return SPDR;
}*/
//sd卡初始化
void MMC_SD_Init(void)
{
	SPI_Init();
	SPI_CS_Deassert();
}

//sd卡写命令
uint8 MMC_SD_SendCommand(uint8 cmd, uint32 arg)
{
	uint8 r1;
	uint8 retry=0;
	
	SPI_WriteByte(0xff);
	SPI_CS_Assert();
	
	SPI_WriteByte(cmd | 0x40);//分别写入命令
	SPI_WriteByte(arg>>24);
	SPI_WriteByte(arg>>16);
	SPI_WriteByte(arg>>8);
	SPI_WriteByte(arg);
	SPI_WriteByte(0x95);
	
	while((r1 = SPI_WriteByte(0xff)) == 0xff)//等待响应，
		if(retry++ > 8) break;//超时退出

	SPI_CS_Deassert();

	return r1;//返回状态值
}

//sd卡复位
uint8 MMC_SD_Reset(void)
{
	uint8 i;
	uint8 retry;
	uint8 r1=0;
	retry = 0;
	SPI_Low();
	do
	{
		for(i=0;i<10;i++) SPI_WriteByte(0xff);
		r1 = MMC_SD_SendCommand(0, 0);//发idle命令
		retry++;
		if(retry>10) return 1;//超时退出
	} while(r1 != 0x01);


	retry = 0;
	do
	{
		r1 = MMC_SD_SendCommand(1, 0);//发active命令
		retry++;
		if(retry>100) return 1;//超时退出
	} while(r1);
	SPI_High();
	r1 = MMC_SD_SendCommand(59, 0);//关crc

	r1 = MMC_SD_SendCommand(16, 512);//设扇区大小512

	return 0;//正常返回
}

//读一个扇区
uint8 MMC_SD_ReadSingleBlock(uint32 sector, uint8* buffer)
{
	uint8 r1;
	uint16 i;
	//uint8 retry=0;

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

	SPI_CS_Assert();
	//等数据的开始
	while(SPI_WriteByte(0xff) != 0xfe);//if(retry++ > 50){SPI_CS_Deassert();return 1;}

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

	SPI_WriteByte(0xff);//伪crc
	SPI_WriteByte(0xff);
	
	SPI_CS_Deassert();

	return 0;
}


//写一个扇区
uint8 MMC_SD_WriteSingleBlock(uint32 sector, uint8* buffer)
{
	uint8 r1;
	uint16 i;
	//uint8 retry=0;

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

	SPI_CS_Assert();
	
	SPI_WriteByte(0xff);
	SPI_WriteByte(0xff);
	SPI_WriteByte(0xff);

	SPI_WriteByte(0xfe);//发开始符
	
	for(i=0; i<512; i++)//送512字节数据
	{
		SPI_WriteByte(*buffer++);
	}
	
	SPI_WriteByte(0xff);
	SPI_WriteByte(0xff);
	
	r1 = SPI_WriteByte(0xff);
	
	if( (r1&0x1f) != 0x05)//等待是否成功
	{
		SPI_CS_Deassert();
		return r1;
	}
	//等待操作完
	while(!SPI_WriteByte(0xff));//if(retry++ > 50){SPI_CS_Deassert();return 1;}

	SPI_CS_Deassert();

	return 0;
}