单片机读写SD卡最简单最基本的程序
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void read_data(U8 *buffer)
{
U32 i;
U8 rsp = 0;
while(!(rsp == 0xfe)) //答应字节的最低为0则代表起始位
rsp = spi_read_byte();
for(i = 0;i < BLOCK_LEN; i++) //读一个block的内容，一般为512字节
buffer = spi_read_byte();
for(i = 0; i < 2; i++) //读两个CRC校正码
send_clk();
send_clk(); //读结束字节
}
U8 write_data(U8 *buffer)
{
U16 rsp = 0, tmp = 0, busy = 0, i = 6;
spi_rt_mode();
spi_write_byte(0xfe); //起始位
for(i = 0; i < 512; i++) //发送512个字节
spi_write_byte(buffer);
for(i = 0; i < 2; i++) //发送16位的CRC校正
spi_write_byte(0xff);
spi_ro_mode(); //等待答应
while(!(rsp == 0x1))
{
rsp =(U16)spi_read_byte();
tmp = rsp;
rsp &= 0x11;
}
while(!(busy == 0xff)) //判忙
{
busy = spi_read_byte();
}
tmp &= 0xe;
if (tmp == 4)
return NO_ERR;
else
{
Uart_Printf("writing error!!!");
return WR_SGL_BLK_ERR;
}
}
U8 read_register(U8 len, U8 *buffer)
{
U8 rsp = 0xff, i = 0;
spi_ro_mode();
while((rsp == 0xff) && (i < 100))
{
rsp=spi_read_byte();
}
if (i > 99)
{
Uart_Printf("ERR in readding register!!!");
return rsp;
}
if (rsp != 0xfe)
{
buffer[0] = rsp;
i = 1;
}
else
i = 0;
for( ; i < len; i++)
buffer = spi_read_byte();
for(i = 0; i < 2; i++ )
send_clk();
send_clk();
return NO_ERR;
}
void send_clk()
{
rSIOCON |= (1 << 3); //使能SPI
while (!(rINTPND & BIT_SIO)); //等待发送完毕
rI_ISPC|=BIT_SIO; //清除中断标志
}
void spi_write_byte(U8 dat)
{
rSIODAT = dat;
send_clk(); //SPI发送
}
U8 spi_read_byte(void)
{
send_clk(); //SPI发送
return rSIODAT;
}
void spi_port_init()
{
rIVTCNT = 0;
rPCONF = (rPCONF & 0xe3ff) | 0x1B0C00; //除了CLK，茶叶MISO，MOSI外，不改变其他位
rPUPF |= 0x160; //使能MISO的上拉电阻
}
#ifndef _SD_CONG
#define _SD_CONG
#define BLOCK_LEN (512) //一个block的长度
#define CMD0 0
#define CMD1 1 // 读OCR寄存器
#define CMD9 9 // 读CSD寄存器
#define CMD10 10 // 读CID寄存器
#define CMD12 12 // 停止读多块时的数据传输
#define CMD13 13 // 读 Card_Status 寄存器
#define CMD16 16 // 设置块的长度
#define CMD17 17 // 读单块
#define CMD18 18 // 读多块,直至主机发送CMD12
#define CMD24 24 // 写单块
#define CMD25 25 // 写多块
#define CMD27 27 // 写CSD寄存器
#define CMD28 28 // Set the write protection bit of the addressed group
#define CMD29 29 // Clear the write protection bit of the addressed group
#define CMD30 30 // Ask the card for the status of the write protection bits
#define CMD32 32 // 设置擦除块的起始地址
#define CMD33 33 // 设置擦除块的终止地址
#define CMD38 38 //擦除所选择的块
#define CMD42 42 // 设置/复位密码或上锁/解锁卡
#define CMD55 55 // 禁止下一个命令为应用命令
#define CMD56 56 // 应用命令的通用I/O
#define CMD58 58 // 读OCR寄存器
#define CMD59 59 // 使能或禁止
//错误返回
#define INIT_FAIL 0
#define NO_ERR 1
#define WR_SGL_BLK_ERR 2
#define GET_INFO_ERR 3
#define R1 1 //SD卡答应类型，表示一个字节
#define R2 2 //SD卡答应类型，表示两个字节
//一下是移植时需修改的内容
#define SD_desel() rPDATE=0x20; //使能SD卡
#define SD_sel() rPDATE=0x00; //放开SD卡
#define spi_high_speed() rSBRDR = 5; //spi高速模式
#define spi_low_speed() rSBRDR = 99; //spi低速模式
#define spi_ro_mode() rSIOCON = (0x0 << 7) | (0x0 << 6) | (0x0 << 5) | (0x0 << 4) | (0x0 << 3) | (0x0 << 2) | 0x1 //只读模式
#define spi_rt_mode() rSIOCON = (0x0 << 7) | (0x0 << 6) | (0x1 << 5) | (0x0 << 4) | (0x0 << 3) | (0x0 << 2) | 0x1 //读写模式
#endif
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