How can I read capacity of SD card ?

[bianchi77]

Guys, I've been trying to read the capacity of sd card, but always fail, anything that I can work around ?
thanks for reading and helping,

Here's the function :

uint32 MMC_SD_ReadCapacity()
{
	uint8 r1;
	uint16 i;
	uint16 temp;
	uint8 buffer[16];
	uint32 Capacity;
	uint16 retry =0;
	//uint8 retry=0;

	r1 = MMC_SD_SendCommand(9, 0);//дÃüÁî	//send command  //READ CSD
	if(r1 != 0x00)
		return r1;

	SPI_CS_Assert();
	while(SPI_WriteByte(0xff) != 0xfe)if(retry++ > 0xfffe){SPI_CS_Deassert();return 1;}

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

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

	SPI_WriteByte(0xff);// extra 8 CLK

/*********************************/
//	C_SIZE
	i = buffer[6]&0x03;
	i<<=8;
	i += buffer[7];
	i<<=2;
	i += ((buffer[8]&0xc0)>>6);

/**********************************/
//  C_SIZE_MULT

	r1 = buffer[9]&0x03;
	r1<<=1;
	r1 += ((buffer[10]&0x80)>>7);


/**********************************/
// BLOCKNR

	r1+=2;

	temp = 1;
	while(r1)
	{
		temp*=2;
		r1--;
	}
	
	Capacity = ((uint32)(i+1))*((uint32)temp);

/////////////////////////
// READ_BL_LEN

	i = buffer[5]&0x0f;

/*************************/
//BLOCK_LEN

	temp = 1;
	while(i)
	{
		temp*=2;
		i--;
	}
/************************/


/************** formula of the capacity ******************/
//
//  memory capacity = BLOCKNR * BLOCK_LEN
//	
//	BLOCKNR = (C_SIZE + 1)* MULT
//
//           C_SIZE_MULT+2
//	MULT = 2
//
//               READ_BL_LEN
//	BLOCK_LEN = 2
/**********************************************/

//The final result
	
	Capacity *= (uint32)temp;	 
	return Capacity;		
}

 

[Soumyajit]

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