900字范文 > SD卡读卡程序 C语言 IO模拟请问大神些有谁用过SD模式读写SD卡？时序是用单片机IO模拟。...

SD卡读卡程序 C语言 IO模拟请问大神些有谁用过SD模式读写SD卡？时序是用单片机IO模拟。...

时间：2022-01-25 04:20:50

大家读写SD卡怎么不用SD模式方式读取，是SPI方式读取简单?

下面贴一段代码，是在FPGA上程序，只能用SD模式进行读，没有文件系统，没有用AVR硬件实现，

电路图：

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-4-20 17:54 上传

电路说明，SD_DAT3一直给高电平

程序：

#ifndef __SD_Card_H__

#define __SD_Card_H__

#define High 1

#define Low 0

//-------------------------------------------------------------------------

//SD Card Set I/O Direction

#define SD_CMD_IN DDRX.1 = Low

#define SD_CMD_OUTDDRX.1 = High

#define SD_DAT_IN DDRX.2 = Low

#define SD_DAT_OUTDDRX.2 = High

#define SD_CLK_OUTDDRX.3 = High

#define SD_DAT3_OUT DDRX.0 = High

//SD Card Output High/Low

#define SD_CMD_LOWPORTX.1 = Low

#define SD_CMD_HIGH PORTX.1 = High

#define SD_DAT_LOWPORTX.2 = Low

#define SD_DAT_HIGH PORTX.2 = High

#define SD_CLK_LOWPORTX.3 = Low

#define SD_CLK_HIGH PORTX.3 = High

#define SD_DAT3_HIGH PORTX.0 = High

//SD Card Input Read

#define SD_TEST_CMD PINX.1

#define SD_TEST_DAT PINX.2

//-------------------------------------------------------------------------

#define BYTE unsigned char

#define UINT16unsigned int

#define UINT32unsigned long

//-------------------------------------------------------------------------

void Ncr(void);

void Ncc(void);

BYTE response_R(BYTE);

BYTE send_cmd(BYTE *);

BYTE SD_read_lba(BYTE *,UINT32,UINT32);

BYTE SD_card_init(void);

//-------------------------------------------------------------------------

BYTE read_status;

BYTE response_buffer[20];

BYTE RCA[2];

BYTE cmd_buffer[5];

const BYTE cmd0[5] = {0x40,0x00,0x00,0x00,0x00};

const BYTE cmd55[5]= {0x77,0x00,0x00,0x00,0x00};

const BYTE cmd2[5] = {0x42,0x00,0x00,0x00,0x00};

const BYTE cmd3[5] = {0x43,0x00,0x00,0x00,0x00};

const BYTE cmd7[5] = {0x47,0x00,0x00,0x00,0x00};

const BYTE cmd9[5] = {0x49,0x00,0x00,0x00,0x00};

const BYTE cmd16[5]= {0x50,0x00,0x00,0x02,0x00};

const BYTE cmd17[5]= {0x51,0x00,0x00,0x00,0x00};

const BYTE acmd6[5]= {0x46,0x00,0x00,0x00,0x02};

const BYTE acmd41[5] = {0x69,0x0f,0xf0,0x00,0x00};

const BYTE acmd51[5] = {0x73,0x00,0x00,0x00,0x00};

//-------------------------------------------------------------------------

void Ncr(void)

{

SD_CMD_IN;

SD_CLK_LOW;

SD_CLK_HIGH;

SD_CLK_LOW;

SD_CLK_HIGH;

}

//-------------------------------------------------------------------------

void Ncc(void)

{

int i;

for(i=0;i<8;i++)

{

SD_CLK_LOW;

SD_CLK_HIGH;

}

//-------------------------------------------------------------------------

BYTE SD_card_init(void)

{

BYTE x,y;

SD_CMD_OUT;

SD_DAT_IN;

SD_CLK_HIGH;

SD_CMD_HIGH;

SD_DAT_LOW;

read_status=0;

for(x=0;x<40;x++)

Ncr();

for(x=0;x<5;x++)

cmd_buffer[x]=cmd0[x];

y = send_cmd(cmd_buffer);

{

for(x=0;x<40;x++);

Ncc();

for(x=0;x<5;x++)

cmd_buffer[x]=cmd55[x];

y = send_cmd(cmd_buffer);

Ncr();

if(response_R(1)>1) //response too long or crc error

return 1;

Ncc();

for(x=0;x<5;x++)

cmd_buffer[x]=acmd41[x];

y = send_cmd(cmd_buffer);

Ncr();

} while(response_R(3)==1);

Ncc();

for(x=0;x<5;x++)

cmd_buffer[x]=cmd2[x];

y = send_cmd(cmd_buffer);

Ncr();

if(response_R(2)>1)

return 1;

Ncc();

for(x=0;x<5;x++)

cmd_buffer[x]=cmd3[x];

y = send_cmd(cmd_buffer);

Ncr();

if(response_R(6)>1)

return 1;

RCA[0]=response_buffer[1];

RCA[1]=response_buffer[2];

Ncc();

for(x=0;x<5;x++)

cmd_buffer[x]=cmd9[x];

cmd_buffer[1] = RCA[0];

cmd_buffer[2] = RCA[1];

y = send_cmd(cmd_buffer);

Ncr();

if(response_R(2)>1)

return 1;

Ncc();

for(x=0;x<5;x++)

cmd_buffer[x]=cmd7[x];

cmd_buffer[1] = RCA[0];

cmd_buffer[2] = RCA[1];

y = send_cmd(cmd_buffer);

Ncr();

if(response_R(1)>1)

return 1;

Ncc();

for(x=0;x<5;x++)

cmd_buffer[x]=cmd16[x];

y = send_cmd(cmd_buffer);

Ncr();

if(response_R(1)>1)

return 1;

read_status =1; //sd card ready

return 0;

}

//-------------------------------------------------------------------------

BYTE SD_read_lba(BYTE *buff,UINT32 lba,UINT32 seccnt)

{

BYTE c=0;

UINT32i,j;

lba+=101;

for(j=0;j

{

Ncc();

cmd_buffer[0] = cmd17[0];

cmd_buffer[1] = (lba>>15)&0xff;

cmd_buffer[2] = (lba>>7)&0xff;

cmd_buffer[3] = (lba<<1)&0xff;

cmd_buffer[4] = 0;

lba++;

send_cmd(cmd_buffer);

Ncr();

}

while(1)

{

SD_CLK_LOW;

SD_CLK_HIGH;

if(!(SD_TEST_DAT))

break;

}

for(i=0;i<512;i++)

{

BYTE k;

for(k=0;k<8;k++)

{

SD_CLK_LOW;

SD_CLK_HIGH;

c <<= 1;

if(SD_TEST_DAT)

c |= 0x01;

}

*buff=c;

buff++;

}

for(i=0; i<16; i++)

{

SD_CLK_LOW;

SD_CLK_HIGH;

}

read_status = 1;//SD data next in

return 0;

}

//-------------------------------------------------------------------------

BYTE response_R(BYTE s)

{

BYTE a=0,b=0,c=0,r=0,crc=0;

BYTE i,j=6,k;

while(1)

{

SD_CLK_LOW;

SD_CLK_HIGH;

if(!(SD_TEST_CMD))

break;

if(crc++ >100)

return 2;

}

crc =0;

if(s == 2)

j = 17;

for(k=0; k

{

c = 0;

if(k > 0) //for crc culcar

b = response_buffer[k-1];

for(i=0; i<8; i++)

{

SD_CLK_LOW;

if(a > 0)

c <<= 1;

else

i++;

a++;

SD_CLK_HIGH;

if(SD_TEST_CMD)

c |= 0x01;

if(k > 0)

{

crc <<= 1;

if((crc ^ b) & 0x80)

crc ^= 0x09;

b <<= 1;

crc &= 0x7f;

}

if(s==3)

{

if( k==1 &&(!(c&0x80)))

r=1;

}

response_buffer[k] = c;

}

if(s==1 || s==6)

{

if(c != ((crc<<1)+1))

r=2;

}

return r;

}

//-------------------------------------------------------------------------

BYTE send_cmd(BYTE *in)

{

int i,j;

BYTE b,crc=0;

SD_CMD_OUT;

for(i=0; i < 5; i++)

{

b = in[ i ];

for(j=0; j<8; j++)

{

SD_CLK_LOW;

if(b&0x80)

SD_CMD_HIGH;

else

SD_CMD_LOW;

crc <<= 1;

SD_CLK_HIGH;

if((crc ^ b) & 0x80)

crc ^= 0x09;

b<<=1;

}

crc &= 0x7f;

}

crc =((crc<<1)|0x01);

b = crc;

for(j=0; j<8; j++)

{

SD_CLK_LOW;

if(crc&0x80)

SD_CMD_HIGH;

else

SD_CMD_LOW;

SD_CLK_HIGH;

crc<<=1;

}

return b;

}

//-------------------------------------------------------------------------

#endif

这些程序有些我也不明白，贴出来希望大家一起探讨交流，打破网站SD卡用SPI方式读写的垄断局面，哈哈

sd模式下应该有4各data吧，怎么你的只用一个?

SPI模式是1Bit的

SD模式是1Bit或4Bit

SD卡确实也像USB一样分为全速(FULL-SPEED)卡和低速卡(LOW-SPEED)。全速卡支持SPI，

1BIT和4BIT的传输模式，可以工作在0-25MHz,并且可以提供高达10MB/S的传输速率；低速卡

仅支持SPI和1BIT的传输模式，4BIT属于可选模式，可以工作在0-400KHz.

在SD模式下,用软件将数据拆分,计算CRC16的时间都占了大头,实际速度不比SPI模式快多少!

SD模式的读有优势吧。写的时候SD模式下就多了CRC16(刚接触实际的东西，所以不太了解CRC16的时间问题，见笑),但是读不管哪种模式下，不是都有CRC校验的？SD模式到底还有那些优势呢，请教

关注一下,SD的读写方式资料太少,或是英文资料太难看

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SD卡读卡程序 C语言 IO模拟 请问大神些 有谁用过SD模式读写SD卡？时序是用单片机IO模拟。...

SD卡读卡程序 C语言 IO模拟请问大神些有谁用过SD模式读写SD卡？时序是用单片机IO模拟。...