1.如何計算V1.0 SD卡容量
計算C_SIZE:
C_SIZE = (csd[8] >> 6) + ((uint16_t)csd[7] << 2) + ((uint16_t)(csd[6] & 3) << 10);
計算 C_SIZE_MULT:
C_SIZE_MULT = ((csd[10] & 128) >> 7) + ((csd[9] & 3) << 1);
計算READ_BL_LEN:
READ_BL_LEN = csd[5] & 15;
容量:
memory capacity = (C_SIZE+1)*MULT*BLOCK_LEN
memory capacity = (C_SIZE+1)<<(C_SIZE_MULT+2+BLOCK_LEN);
如果需要轉換成Kbyte,左移10位即可實作,也可以把結果除以1024,或者把上面的公式寫成如下:
memory capacity = (C_SIZE+1)<<(C_SIZE_MULT+2+BLOCK_LEN-10);
2.如何計算V2.0 SD卡容量
csize = csd[9] + ((uint32_t)csd[8] << 8) + ((uint32_t)(csd[7] & 63) << 16) + 1;
Capacity = csize << 9;
3.識别SD卡版本
uint32_t SD_GetCapacity(void)
{
uint8_t csd[16];
uint32_t Capacity;
uint16_t n;
uint16_t csize;
if(SD_GetCSD(csd)!=0) return 0;
if((csd[0]&0xC0)==0x40)//判斷bit126是否為1
{
csize = csd[9] + ((uint32_t)csd[8] << 8) + ((uint32_t)(csd[7] & 63) << 16) + 1;
Capacity = csize << 9;
}
else
{
n = (csd[5] & 0x0F) + ((csd[10] & 0x80) >> 7) + ((csd[9] & 0x03) << 1) + 2;
csize = (csd[8] >> 6) + ((uint16_t)csd[7] << 2) + ((uint16_t)(csd[6] & 0x03) << 10) + 1;
Capacity = (uint32_t)csize << (n - 10);
}
return Capacity;
}