sd.c

用LPC2103（ARM7）操作SD卡代码。

/****************************************Copyright (c)**************************************************
**
**											力天电子
**								     http://www.LT430.com
**作者：何呈 
**文件名称：fat.C
**功能：
**说明：
**------------------------------------------------------------------------------------------------------
********************************************************************************************************/

#include "spi.h"
#include "uart.h"
#define uchar unsigned char
#define uint unsigned int
#define MMC_CS_PIN     1<<18
#define MMC_CSH IOSET |= 1<<18 
#define MMC_CSL IOCLR |= 1<<18 

uchar reading=0,a=0,pointer=0;

void sd_port_init()
{
	Init_SPI();
}

uchar BUFFER[512];                   //扇区缓冲区
uint i=0;
void delay_nus(uint n)
{
	unsigned int  b,a;
	for (b = 1; b<n; b++)
			for(a=0;a<15;a++);
} 
//****************************************************************************
//Send a Command to MMC/SD-Card
//Return: the second byte of response register of MMC/SD-Card
//****************************************************************************
uchar SD_Write_Command(uchar cmd,unsigned long arg)
{
   uchar tmp;
   uchar retry=0;
   
   //MMC_CSH; //MMC_PORT|=MMC_CS_PIN;       //SD卡关闭   
   //send 8 Clock Impulse
   Write_Byte_SPI(0xFF);
   //set MMC_Chip_Select to low (MMC/SD-Card active)
   MMC_CSL;//MMC_PORT&=~MMC_CS_PIN;       //SD卡使能
   
   Write_Byte_SPI(cmd|0x40);   //送头命令
   Write_Byte_SPI(arg>>24);
   Write_Byte_SPI(arg>>16);     //send 6 Byte Command to MMC/SD-Card
   Write_Byte_SPI(arg>>8);
   Write_Byte_SPI(arg&0xff);
   Write_Byte_SPI(0x95);       //仅仅对RESET有效的CRC效验码
  
   //get 8 bit response
   //Read_Byte_MMC(); //read the first byte,ignore it. 
   do 
   {  //Only last 8 bit is used here.Read it out. 
      tmp = Read_Byte_SPI();
      retry++;
   }
   while((tmp==0xff)&&(retry<100));  //当没有收到有效的命令的时候
   
   if(reading==0) MMC_CSH;//MMC_PORT|=MMC_CS_PIN;            //MMC_CS_PIN=1;
   else MMC_CSL;//MMC_PORT&=~MMC_CS_PIN;      //MMC_CS_PIN=0;   
   return(tmp);
}
//****************************************************************************
//SD卡初始化(SPI-MODE)
//****************************************************************************
uchar SD_Init(void)
{  
   uchar retry,temp;
   uchar i;
   MMC_CSL;	 		//MMC_PORT&=~MMC_CS_PIN;      //SD卡使能
   delay_nus(250);  //Wait MMC/SD ready...
   for (i=0;i<0x0f;i++) 
   {
      Write_Byte_SPI(0xff); //send 74 clock at least!!!
   }
   //Send Command CMD0 to MMC/SD Card
   retry=0;
   
   do
   { //retry 200 times to send CMD0 command 
     temp=SD_Write_Command(0,0);
     retry++;
     //delay_nus(1);
     if(retry==100) 
     {
        return(0xff); 
     }
   } 
   while(temp!=1);  
   
   //Send Command CMD1 to MMC/SD-Card
   retry=0;
   do
   { //retry 100 times to send CMD1 command 
     delay_nus(3000);
     temp=SD_Write_Command(1,0);
     retry++;
     delay_nus(3000);
     if(retry==200) 
     { 
    	 return(0xff);
     }
   }
   while(temp!=0); 
   retry=0; 
   
   MMC_CSL;	//片选
   SD_Write_Command(16,512);     //设置一次读写BLOCK的长度为512个字节
  
   MMC_CSH;//MMC_PORT|=MMC_CS_PIN;   //MMC_CS_PIN=1;  //set MMC_Chip_Select to high 
   return(0); //All commands have been taken.
} 
//****************************************************************************
//从SD卡读一个扇区  Return 0 if no Error.
//****************************************************************************
uchar SD_Read_Block(unsigned long address)
{  
   uchar temp=0;uint i=0;
   reading=1; 
   temp=SD_Write_Command(17,address);     //读出RESPONSE     
   while (Read_Byte_SPI()!= 0xfe)
   {;}  //直到读取到了数据的开始头0XFE，才继续
   for(i=0; i<512; i++)
   {
   		//delay_nus(1000);
		BUFFER[i]=Read_Byte_SPI();
		//delay_nus(1000);
   }
   Read_Byte_SPI();//CRC - Byte 
   //delay_nus(1000);
   Read_Byte_SPI();//CRC - Byte
   reading=0; 
   //send 8 Clock Impulse
   //delay_nus(1000);
   Write_Byte_SPI(0xFF);
   MMC_CSH;//MMC_PORT|=MMC_CS_PIN;        //关闭SD卡
   return(temp);
}