mmc_sd.c

基於MCU c51/8051 讀寫SD/MMC card 再以USB 傳回電腦的範例程序

/* ELEC254 Group32 USB SD Card Reader */

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

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

void SPI_High(void)
{
	SPCR =  _BV(SPE)|_BV(MSTR);
	SPSR |= _BV(SPI2X);
}


void SPI_Init(void)
{
	DDR_INI();
	SPI_Low();
}

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;
}

void MMC_SD_Init(void)
{
	SPI_Init();
	SPI_CS_Deassert();
	LED_ON();
	
}

uint8 MMC_SD_SendCommand(uint8 cmd, uint32 arg)
{
	uint8 r1;
	uint8 retry=0;
	
	SPI_WriteByte(0xff);
	SPI_WriteByte(0xff);
	SPI_WriteByte(0xff);
	SPI_WriteByte(0xff);
	SPI_WriteByte(0xff);
	SPI_WriteByte(0xff);

	SPI_CS_Assert();
	
	SPI_WriteByte(cmd | 0x40);
	SPI_WriteByte(arg>>24);
	SPI_WriteByte(arg>>16);
	SPI_WriteByte(arg>>8);
	SPI_WriteByte(arg);
	SPI_WriteByte(0x95);
	
	while((r1 = SPI_WriteByte(0xff)) == 0xff)
		if(retry++ > 100) break;  //time out error

	SPI_CS_Deassert();

	return r1;
}

uint8 MMC_SD_Reset(void)
{
	uint8 i;
	uint8 retry;
	uint8 r1=0;
	retry = 0;
	SPI_Low();

	do
	{
		for(i=0;i<100;i++) SPI_WriteByte(0xff);
		r1 = MMC_SD_SendCommand(0, 0);	//send idle command
		retry++;
		if(retry>10) return 1;	//time out
	} while(r1 != 0x01);	


	retry = 0;
	do
	{
		r1 = MMC_SD_SendCommand(1, 0);	//send active command
		retry++;
		if(retry>100) return 1;	//time out
	} while(r1);
	SPI_High();
	r1 = MMC_SD_SendCommand(59, 0);	//disable CRC

	r1 = MMC_SD_SendCommand(16, 512);	//set sector size to 512
	return 0;	
}


uint8 MMC_SD_ReadSingleBlock(uint32 sector, uint8* buffer)
{
	uint8 r1;
	uint16 i;
	uint8 retry=0;

	do
	{
		r1 = MMC_SD_SendCommand(17, sector<<9);	//read command
		retry++;
		if(retry>10) return 1;	//time out
	} while(r1 != 0x00);	


	SPI_CS_Assert();
	//wait to start recieve data
	while(SPI_WriteByte(0xff) != 0xfe);

	for(i=0; i<512; i++)	//read 512 bytes
	{
		*buffer++ = SPI_WriteByte(0xff);
	}

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

	return 0;
}


uint8 MMC_SD_WriteSingleBlock(uint32 sector, uint8* buffer)
{
	uint8 r1;
	uint16 i;
	uint8 retry=0;

	do
	{
		r1 = MMC_SD_SendCommand(24, sector<<9);//send command
		retry++;
		if(retry>10) return 1;		//time out
	} while(r1 != 0x00);	



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

	SPI_WriteByte(0xfe);			//send start byte
	
	for(i=0; i<512; i++)		//send 512 bytes data
	{
		SPI_WriteByte(*buffer++);
	}
	
	SPI_WriteByte(0xff);
	SPI_WriteByte(0xff);
	
	r1 = SPI_WriteByte(0xff);
	
	if( (r1&0x1f) != 0x05)
	{
		SPI_CS_Deassert();
		return r1;
	}
			
	while(!SPI_WriteByte(0xff));

	SPI_CS_Deassert();

	return 0;
}

uint32_t MMC_SD_ReadCapacity()
{
	uint8 r1;
	uint16 i;
	uint16 temp;
	uint8 buffer[16];
	uint32 Capacity;

	r1 = MMC_SD_SendCommand(9, 0);
	if(r1 != 0x00)
		return r1;

	SPI_CS_Assert();
	while(SPI_WriteByte(0xff) != 0xfe);
	
	for(i=0;i<16;i++)
	{
		buffer[i]=SPI_WriteByte(0xff);
	}	

	SPI_WriteByte(0xff);
	SPI_WriteByte(0xff);
	
	SPI_WriteByte(0xff);
	
	SPI_CS_Deassert();

	i = buffer[6]&0x03;
	i<<=8;
	i += buffer[7];
	i<<=2;
	i += ((buffer[8]&0xc0)>>6);
	r1 = buffer[9]&0x03;
	r1<<=1;
	r1 += ((buffer[10]&0x80)>>7);

	r1+=2;

	temp = 1;
	while(r1)
	{
		temp*=2;
		r1--;
	}
	
	Capacity = ((uint32)(i+1))*((uint32)temp);
	i = buffer[5]&0x0f;
	temp = 1;
	while(i)
	{
		temp*=2;
		i--;
	}

	Capacity *= (uint32)temp;	 
	return Capacity;		
}