pcf8574.c

PCF8574的读写

#include <w77e58.h>    
#include <stdio.h>   
#include <stdlib.h>                      /* standard library .h-file          */
#include <math.h>
#include <absacc.h>
#include <intrins.h>
#define NOP _nop_();
#define	WriteDeviceAddress 0xa0		
#define	ReadDviceAddress 0xa1	
sbit	Ram_protect=P1^2;	
sbit	SCL=P1^1;	// I2C serial clock line.
sbit	SDA=P1^0;	// I2C serial data line.
#define uint unsigned int
#define uchar unsigned char
/* -------------定义器件地址--------------*/
unsigned char PCFKey		=0x40;	// 键盘8574地址
unsigned char PCFLed		=0x4E;	// 指示灯8574地址????????????
extern I2CStart();
extern I2CStop();
extern uchar readbyte(void);
extern writebyte(uchar input);
/*--------------------- WatchDog -------------------------*/
void WatchDog(void)
{	
	TA=0xAA	;	//3M/C	Note:M/C=Machine Cycles
    	TA=0x55	;	//3M/C
	RWT=1;		//Reset Watchdog timer
	led0=~led0;
} 
void DelayMs(int number) 	//延时1Ms
{
	uchar idata temp;
	for(;number!=0;number--)
	{
		for(temp=167;temp!=0;temp--) {
		}
		WatchDog();
	}
}
void long_delay(void)
{
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}
/*  在时钟线（SCL）为高电平其间，数据线（SDA）由高变低，将产生一个开始信号。-------*/
void I2CStart() {
	SDA=1;
	long_delay();
	SCL=1;
	long_delay();
	SDA=0;
	long_delay();
	SCL=0;
	long_delay();
}
/*  在时钟线（SCL）为高电平其间，数据线（SDA）由低变高，将产生一个停止信号。-------*/
void I2CStop() {
	SCL=0;
	long_delay();
	SDA=0;
	long_delay();
	SCL=1;
	long_delay();
	SDA=1;
	long_delay();
}
/*-------------------------------------------------------------------------*/
void Ack() {
	SDA=0;
	SCL=1;
	SCL=0;
	SDA=1;
}
/*-------------------------------------------------------------------------*/
void NoAck() {
	SDA=1;
	SCL=1;
	SCL=0;
}
/*-------------------------------------------------------------------------*/
bit TestAck(void) {
	bit ErrorBit;
	SDA=1;
	long_delay();
	SCL=1;
	long_delay();
	ErrorBit=SDA;
	long_delay();
	SCL=0;
	long_delay();
	return(ErrorBit);
}
/*-------------------------------------------------------------------------*/
void Write8Bit(unsigned char input) {
	unsigned char temp;
	for(temp=8;temp!=0;temp--) {
		SDA=(bit)(input&0x80);
		SCL=1;
		SCL=0;
		input=input<<1;
	}
}
/*-------------------------------------------------------------------------*/
void Write24c02(unsigned char *Wdata,unsigned char RomAddress,unsigned char number) 
{
	Ram_protect=0;
	I2CStart();
	Write8Bit(WriteDeviceAddress);
	TestAck();
	Write8Bit(RomAddress);
	TestAck();
	for(;number!=0;number--) {
		Write8Bit(*Wdata);
		TestAck();
		Wdata++;
	}
	I2CStop();
	//DelayMs(20);
	Ram_protect=1;
}
/***********writebyte()***********/
void writebyte(unsigned char input)
{
	unsigned char idata temp;
	for(temp=8;temp!=0;temp--) {
		SDA=(bit)(input&0x80);
		SCL=1;
		long_delay();
		SCL=0;
		long_delay();
		input=input<<1;
	}
	TestAck();
}
/***********readbyte()***************/
//并口读取I2C总线的数据时，必须让 T1截止，使用并口的13脚来接收SDA上的数据。
unsigned char readbyte(void){
	unsigned char idata temp,rbyte=0;
	for(temp=8;temp!=0;temp--)
	{
		SCL=1;
		rbyte=rbyte<<1;
		rbyte=rbyte|((unsigned char)(SDA));
		SCL=0;
	}
	return(rbyte);
}
unsigned char Read8Bit() 
{
	unsigned char temp,rbyte=0;
	for(temp=8;temp!=0;temp--) {
		SCL=1;
		rbyte=rbyte<<1;
		rbyte=rbyte|((unsigned char)(SDA));
		SCL=0;
	}
	return(rbyte);
}
/*-------------------------------------------------------------------------*/
void Read24c02(unsigned char *RamAddress,unsigned char RomAddress,unsigned char bytes)
{	
	Ram_protect=0;
	I2CStart();
	Write8Bit(WriteDeviceAddress);
	TestAck();
	Write8Bit(RomAddress);
	TestAck();
	I2CStart();
	Write8Bit(ReadDviceAddress);
	TestAck();
	while(bytes!=1)
	{
		*RamAddress=Read8Bit();
		Ack();
		RamAddress++;
		bytes--;
	}
	*RamAddress=Read8Bit();
	NoAck();
	I2CStop();
	Ram_protect=1;
}
/*-------------写PCF8574--------------------------*/
void writepcf8574(uchar slvadr,uchar dat)
{
	I2CStart();//START();				//启动I2C 总线
	writebyte(slvadr);
	writebyte(dat);
	I2CStop();
}
/*-------------读PCF8574--------------------------*/
uchar readpcf8574(uchar slvadr)
{
	uchar idata dat;
	I2CStart();//START();				//启动I2C 总线
	writebyte(slvadr);
	I2CStart();
	writebyte(slvadr+1);
	dat=readbyte();
	I2CStop();
	return(dat);
}
/*---------------------Keyboard Scan Routins----------------*/
/*出口信息:SGKEY中存键值,无键按下,键值=FF.*/
uchar KBSCAN(void)
{
	uchar idata data0,data1;
	uchar idata key;			//键值
	writepcf8574(PCFKey,0xF0);		//写键盘8574
	data0=readpcf8574(PCFKey);		//读键盘8574
	if(data0!=0xF0)				//是否有键按下?
	{
		data0=~data0;
		data0&=0xF0;
		DelayMs(10);			//延时去抖
		writepcf8574(PCFKey,0x0F);
		data1=readpcf8574(PCFKey);
		if(data1!=0x0F)			//是否有键按下?
		{
			data1=~data1;
			data1&=0x0F;
			key=data0+data1;
		}
		else
			key=0xFF;
		//判断按键是否放开
		writepcf8574(PCFKey,0xF0);
		data0=readpcf8574(PCFKey);
		while(data0!=0xF0)
		{
			writepcf8574(PCFKey,0xF0);
			data0=readpcf8574(PCFKey);
			WatchDog();
		}
	}
	else
		key=0xFF;
	return(key);
}