iic.c

此程序实现IIC通信

#include <reg52.h>
#include<intrins.h>
#define uchar unsigned char
#define uint unsigned int
#define IIC_READ  0XA1   //定义读指令
#define IIC_WRITE 0XA0   //定义写指令
#define NOP _nop_(); _nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_()

//==============================

sbit 	SDA=P0^6;		
sbit 	SCL=P0^7;		

//===============================
//define a bit_operation byte to use in shift operation
//use this mode can achieve high operation speed 
uchar bdata bbyte;//定义位操作用数组，采用此方法可提高位操作速度
sbit a0=bbyte^0;
sbit a1=bbyte^1;
sbit a2=bbyte^2;
sbit a3=bbyte^3;
sbit a4=bbyte^4;
sbit a5=bbyte^5;
sbit a6=bbyte^6;
sbit a7=bbyte^7;
//========================================
bit IFACK;	//record the SDA state to confirn if ACK has happened 
bit NO_ACK;	//no ack flag
bit BUS_FAULT;	//bus fault flag
//========================================
//FUNCTION:ROUTES TO PROVIDE A START SIGNAL
void start(void)
{
	SCL=0;SDA=1; NOP;SCL=1;SDA=0;NOP;SCL=0;
}
//=======================================
//FUNCTION:ROUTES TO PROVIDE A STOP SIGNAL
void stop(void)
{
	SCL=0;SDA=0;NOP;SCL=1;SDA=1;NOP;SCL=0;
}
//=====================================
//FUNCTION:ROUTES TO PROVIDE ACK SINGAL
void ack(void)
{
	SCL=0;SDA=0;NOP;SCL=1;NOP;SCL=0;
}
//=====================================
//FUNCTION:ROUTES TO RELEASE THE SDA TO RECEIVE A ACK SIGNAL 
//	             OR TO PROVIDE A NO_ACK SIGNAL
//type=1等待应答信号
//type=0 产生无应答信号
void nack(uchar type)
{
	SCL=0;SDA=1;NOP;SCL=1;IFACK=SDA; NOP;SCL=0;
	if(type)
	{
		if(IFACK)//如果无应答信号，则置标志位NO_ACK,程序中止
		{	
			NO_ACK=1;//用户可以加入自己的异常处理程序
			//while(1);
		}
		else NO_ACK=0;
	}
}
//=======================================================
//FUNCTION:THE IIC DEVICE SHIFT OUT A BYTE  TO THE MASTER
uchar  inbyte(void) 
{//从IIC器件中读出数据
	SDA=1;
	SCL=1;a7=SDA;NOP;SCL=0;
	SCL=1;a6=SDA;NOP;SCL=0;
	SCL=1;a5=SDA;NOP;SCL=0;
	SCL=1;a4=SDA;NOP;SCL=0;
	SCL=1;a3=SDA;NOP;SCL=0;
	SCL=1;a2=SDA;NOP;SCL=0;
	SCL=1;a1=SDA;NOP;SCL=0;
	SCL=1;a0=SDA;NOP;SCL=0;
	return(bbyte);
}
//=======================================================
//FUNCTION:THE IIC DEVICE SHIFT IN A BYTE FROM THE MASTER 
void outbyte(uchar outdata)
 {//将数据写放IIC器件
	bbyte=outdata;
	SDA=a7;SCL=1;NOP;SCL=0;
	SDA=a6;SCL=1;NOP;SCL=0;
	SDA=a5;SCL=1;NOP;SCL=0;
	SDA=a4;SCL=1;NOP;SCL=0;
	SDA=a3;SCL=1;NOP;SCL=0;
	SDA=a2;SCL=1;NOP;SCL=0;
	SDA=a1;SCL=1;NOP;SCL=0;
	SDA=a0;SCL=1;NOP;SCL=0;
}

/**********************写函数****************************************
**   函数名称:  写数据 
**   入口参数：add为读起始地址，ptr数据保存指针,writelen为写出数据长度
********************************************************************/
void writebyteseq(unsigned char page_addr, unsigned char byte_address,uchar *ptr,uchar writelen)
{
uchar temph;
	uchar i;
	unsigned char x;
	 x = (page_addr<<1);                         
     temph = (x | IIC_WRITE);  
	start(); 		
//	outbyte(IIC_WRITE);		
//	nack(1);		
	outbyte(temph);
	nack(1);
	outbyte(byte_address);
	nack(1);
	for(i=0;i<writelen;i++)
	{
		outbyte(*(ptr+i));
		nack(1);
	}
	stop();	
}
/**********************读函数***************************************
**   函数名称:  连续读数据 
**   入口参数：add为读起始地址，ptr数据保存指针,readlen为读出数据长度
********************************************************************/
void readbyteseq(unsigned char page_addr, unsigned char byte_address,uchar *ptr,uchar readlen)
{
	uchar temph;
	uchar i;
	unsigned char x;
	 x = (page_addr<<1);                          // 2 address bytes.
     temph = (x | IIC_WRITE);  
	start();
//	outbyte(IIC_WRITE);
//	nack(1);
	outbyte(temph);
	nack(1);
	outbyte(byte_address);
	nack(1);
	start();
	outbyte(IIC_READ);
	nack(1);
	for(i=0;i<readlen-1;i++)
	{
		*(ptr+i)=inbyte();
		ack();		
	}
	*(ptr+readlen-1)=inbyte();
	nack(0);
	stop();
}