SD Cards (Part 5)
Other posts on same subject Part 1, 2, 3, 4, 5, 6
Erratum!
While building a professional grade application I realized that I made a stupid mistake in the Blocks function from my PlainSDC library. Firstly, here is a nice table showing the content of the CARD SPECIFIC DATA REGISTER:
It is taken from the ‘APPLICATION NOTE 3969: SD Media Format Expands the MAXQ2000’s Space for Nonvolatile Data Storage’ edited by MAXIM DALLAS.
And now is the correct code
uint32_t PlainSDC::Blocks(void)
/* Get nbr of blocks on SD memory card */
{
uint8_t vBuffer[16];
/* Read SD Card Size Details */
ReadRegister(vBuffer, SDC_SEND_CSD);
/* Compute size */
uint32_t C_Size = 0;
C_Size |= ((vBuffer[6] & 0x03) << 10);
C_Size |= ((vBuffer[7] & 0xFF) << 2);
C_Size |= ((vBuffer[8] & 0xC0) >> 6);
uint32_t C_Size_Mult = 0;
C_Size_Mult |= ((vBuffer[9] & 0x03) << 1);
C_Size_Mult |= ((vBuffer[10] & 0x80) >> 7);
return ((C_Size + 1) << (C_Size_Mult + 2));
};
And a little compensation gift: an additional function which computes the size of the read blocks!
uint16_t PlainSDC::BlockSize(void)
/* Get size of blocks on SD memory card */
{
uint8_t vBuffer[16];
/* Read SD Card Size Details */
ReadRegister(vBuffer, SDC_SEND_CSD);
/* Compute size */
uint16_t READ_BL_LEN = 0;
READ_BL_LEN |= ((vBuffer[5] & 0x0F) );
return (1 << READ_BL_LEN);
};
[…] Next post on same subject Tags: SD Cards Comment (RSS) | Trackback […]