AVR的SD卡接口程序

SD卡接口程序/*****************************************************/
/*?????????? SD Code for?? M32L???????????? */
/*?????? By?? pasyong??????? */
/*?????? 2006-4???????? */
/*?????? Base ICC6.31A???????????? */
/************************************************************/
#include
#include
#include "1011.h"
#define uchar unsigned char
#define uint unsigned int
#define MMC_CS_PIN???? BIT(4)??? //PORTB.4
#define MMC_PORT?????? PORTB???

?uchar reading=0,a=0,pointer=0;
void sd_port_init()
{
MMC_PORT =MMC_CS_PIN;
}
uchar BUFFER[512];?????????????????? //扇區緩沖區
uint i=0;
void delay_nus(uint n)
?{
?unsigned char? b;
? for (b = 1; b?? ;
?}
//************************************************************
//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_PORT =MMC_CS_PIN;?????? //SD卡關閉??
?? //send 8 Clock Impulse
?? Write_Byte_SPI(0xFF);
??
?? //set MMC_Chip_Select to low (MMC/SD-Card active)
? MMC_PORT&=~MMC_CS_PIN;?????? //SD卡使能

?? Write_Byte_SPI(cmd 0x40);?? //送頭命令
?? 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);?????? //僅僅對RESET有效的CRC效驗碼
?
?? //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));? //當沒有收到有效的命令的時候
??
?? if(reading==0)
?? MMC_PORT =MMC_CS_PIN;??????????? //MMC_CS_PIN=1;
?? else 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_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++;
???? if(retry==100)
???? {
????? ;//CMD0 Error!
???? }
?? }
?? while(temp!=1);?
??
?? //Send Command CMD1 to MMC/SD-Card
?? retry=0;
?? do
?? { //retry 100 times to send CMD1 command
???? temp=SD_Write_Command(1,0);
???? retry++;
???? if(retry==100)
???? {
???? ;
???? }
?? }
?? while(temp!=0);
?? retry=0;
??? SD_Write_Command(16,512);???? //設置一次讀寫BLOCK的長度為512個字節
?
?? MMC_PORT =MMC_CS_PIN;?? //MMC_CS_PIN=1;? //set MMC_Chip_Select to high
?? return(0); //All commands have been taken.
}
//****************************************************************
//從SD卡讀一個扇區? 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);???? //讀出RESPONSE????
?? while (Read_Byte_SPI()!= 0xfe)
?? {;}? //直到讀取到了數據的開始頭0XFE,才繼續
?? for(i=0; i<512; i++)
?{
?BUFFER[i]=Read_Byte_SPI();
?}
?? Read_Byte_SPI();//CRC - Byte
?? Read_Byte_SPI();//CRC - Byte
?? reading=0;
?? MMC_PORT =MMC_CS_PIN;??????? //關閉SD卡
?? return(temp);
}