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实现代码

main.c

#include <STC15F2K60S2.H>
#include "iic.h"
#include "intrins.h"

#define uchar unsigned char 
#define uint unsigned int 

sbit TX = P1^0;  //发射引脚
sbit RX = P1^1;  //接收引脚

sbit L1 = P0^0;
sbit L2 = P0^1;
sbit L3 = P0^2;
sbit L8 = P0^7;

sbit S7 = P3^0;
sbit S6 = P3^1;
sbit S5 = P3^2;
sbit S4 = P3^3;

uchar jm = 0;
code uchar tab[] = {0xC0, 0xF9,0xA4,0xB0,0x99,0x92,0x82,0xF8,0x80,0x90, 0xff, 0xc1, 0x8c, 0xc3, 0x88};
//U P L A 11 12 13 14


//初始化为0，一次表示从左至右分别表示S5的参数选择为上限，超声波的连续测量标志不打开，L8灭
bit flag_para, flag_start, flag_L8 ;

float Vup = 4.5, Vdown = 0.5, Vrb2, Vdac;
uint dis = 5;

void sys_init();
void dac_pcf8591(uchar da);
uchar rd_pcf8591(uchar addr);
void Delay5ms();		//@12.000MHz
void Delay12us();		//@12.000MHz 用于延时与产生方波

void key_handle();
void delay_k(uchar t);
void Send_Sonic();//用于发送8个40kHz的方波
void Sonic_handle();
void led();
void dac_handle();

void dsp_smg_bit(uchar pos, val, dot);
void display();
void dsp_vol();
void dsp_para();
void dsp_dis();
void Delay1ms();		//@12.000MHz

void main()
{
	sys_init();
	while(1)
	{
		Vrb2 = rd_pcf8591(0x43) * 5 / 255.0;//读取通道3的电压，要同时允许DAC
		key_handle();
		display();
		Sonic_handle();
		led();
		dac_handle();
	}
}
void dac_handle()
{
	if (!flag_start)
	{
		Vdac = 0.0;
	}
	else 
	{
		if (dis <= 20)
			Vdac = 1.0;
		else if (dis >= 80)
			Vdac = 5.0;
		else 
		{
			Vdac = 1.0 / 15 * (dis - 20) + 1;
		}
	}
	dac_pcf8591((uchar)(Vdac * 51));
}
void led()
{
	if (0 == jm)
	{
		P2 = (P2 & 0x1f) | 0x80;
		L1 = 0;
	}
	else if (1 == jm)
	{
		P2 = (P2 & 0x1f) | 0x80;
		L2 = 0;
	}
	else if (2 == jm)
	{
		P2 = (P2 & 0x1f) | 0x80;
		L3 = 0;
	}
	
	if (flag_start)
	{
		if (flag_L8)
		{
			P2 = (P2 & 0x1f) | 0x80;
			L8 = 0;
		}
		else 
		{
			P2 = (P2 & 0x1f) | 0x80;
			L8 = 1;
		}
	}
	
}
void Sonic_handle()
{
	if (jm != 2)//电压上限、下限参数在参数调整过程中无效，通过 S4 按键退出参数界面时生效。
	{
		flag_start = (Vrb2 > Vdown && Vrb2 < Vup);
	}
	if (flag_start)//连续测量
	{
		uint t = 0;
		Send_Sonic();
		AUXR &= 0XBF;
		TMOD &= 0X0F;
		TL1 = 0;
		TH1 = 0;
		TF1 = 0;
		
		TR1 = 1;
		while((RX == 1) && (TF1 == 0));//等待超声波信号返回(RX引脚变为低电平)或等超出测量范围
		TR1 = 0;
		if(TF1 == 0)  //正常范围内
		{
			t = (TH1 << 8) | TL1;
			dis = t * 0.172 / 10;
		}
		else
		{
			TF1 = 0;
			dis = 999;
		}
	}
}
void Send_Sonic()
{
	uchar i;
	for (i = 0; i < 8; i++)
	{
		TX = 1;
		Delay12us();
		TX = 0;
		Delay12us();
	}
}

void Delay12us()		//@12.000MHz
{
	unsigned char i;
 
	_nop_();
	_nop_();
	i = 33;
	while (--i);
}

void dsp_dis()
{
	dsp_smg_bit(1, 13, 0);
	if (flag_start)
	{
		if (dis > 99)
			dsp_smg_bit(6, dis / 100 % 10, 0);
		if (dis > 9)
			dsp_smg_bit(7, dis / 10 % 10, 0);
		if (dis >= 0)
			dsp_smg_bit(8, dis % 10, 0);
	}
	else 
	{
		dsp_smg_bit(6, 14, 0);
		dsp_smg_bit(7, 14, 0);
		dsp_smg_bit(8, 14, 0);
	}
}

void dsp_para()
{
	uchar x = (uchar)(Vup * 10);
	uchar y = (uchar)(Vdown * 10);
	dsp_smg_bit(1, 12, 0);
	
	dsp_smg_bit(4, x / 10, 1);
	dsp_smg_bit(5, x % 10, 0);
	
	dsp_smg_bit(7, y / 10, 1);
	dsp_smg_bit(8, y % 10, 0);
}
void dsp_vol()
{
	uint x = (uint)(Vrb2 * 100);
	dsp_smg_bit(1, 11, 0);
	dsp_smg_bit(6, x / 100, 1);
	dsp_smg_bit(7, x / 10 % 10, 0);
	dsp_smg_bit(8, x % 10, 0);
}
void dsp_smg_bit(uchar pos, val, dot)
{
	P2 = (P2 & 0x1f) | 0xc0;
	P0 = 1 << (pos - 1);
	
	P2 = (P2 & 0x1f) | 0xe0;
	if (!dot)
		P0 = tab[val];
	else
		P0 = tab[val] & 0x7f;
		
	Delay1ms();
	P0 = 0xff;
	P2 &= 0x1f;
}
void display()
{
	if (0 == jm)
		dsp_vol();
	else if(2 == jm)
		dsp_para();
	else if (1 == jm)
		dsp_dis();
}
void Delay1ms()		//@12.000MHz
{
	unsigned char i, j;

	i = 12;
	j = 169;
	do
	{
		while (--j);
	} while (--i);
}

void delay_k(uchar t)
{
	while(t--)
		display();
}
void key_handle()
{
	if (!S7)//-
	{
		delay_k(15);
		if (!S7)
		{
			while(!S7)
				display();
			if (2 == jm)
			{
				if (!flag_para)
				{
					if (Vup > 0.5)
						Vup -= 0.5;
					else 
						Vup = 5.0;
				}
				else 
				{
					if (Vdown > 0.5)
						Vdown -= 0.5;
					else 
						Vdown = 5.0;
				}
			}
			///
		}
	}
	
	if (!S6)//+
	{
		delay_k(15);
		if (!S6)
		{
			if (2 == jm)
			{
				if (!flag_para)
				{
					if (Vup <= 4.5)
						Vup += 0.5;
					else 
						Vup = 0.5;
				}
				else 
				{
					if (Vdown <= 4.5)
						Vdown += 0.5;
					else 
						Vdown = 0.5;
				}
			}
			
			while(!S6)
				display();
		}
	}
	
	if (!S5)//参数选择
	{
		delay_k(15);
		if (!S5)
		{
			flag_para = !flag_para;
			while(!S5)
				display();
		}
	}
	if (!S4)//界面切换
	{
		delay_k(15);
		if (!S4)
		{
			if (++jm >= 3)
				jm = 0;
			if (2 == jm)
				flag_para = 0;
			while(!S4)
				display();
		}
	}
}
uchar rd_pcf8591(uchar addr)
{
	uchar da;
	IIC_Start();
	IIC_SendByte(0x90);
	IIC_WaitAck();
	
	IIC_SendByte(addr);
	IIC_WaitAck();
	Delay12us();
	
	IIC_Start();
	IIC_SendByte(0x91);
	IIC_WaitAck();

	da = IIC_RecByte();
	IIC_SendAck(1);
	IIC_Stop();
	
	return da;
}
void dac_pcf8591(uchar da)
{
	IIC_Start();
	IIC_SendByte(0x90);
	IIC_WaitAck();
	
	IIC_SendByte(0x43);
	IIC_WaitAck();
	
	IIC_SendByte(da);
	IIC_WaitAck();
	IIC_Stop();
	Delay5ms();
}

void Delay5ms()		//@12.000MHz
{
	unsigned char i, j;

	i = 59;
	j = 90;
	do
	{
		while (--j);
	} while (--i);
}

void timer0() interrupt 1
{
	static uchar i1;
	if (flag_start)
	{
		if (++i1 == 2)
		{
			i1 = 0;
			flag_L8 = !flag_L8;
		}
	}
}
void sys_init()
{
	P2 = (P2 & 0x1f) | 0xa0;
	P0 = 0xaf;
	
	P2 = (P2 & 0x1f) | 0x80;
	P0 = 0xff;
	P2 &= 0x1f;
	
	AUXR &= 0x7F;		//定时器时钟12T模式
	TMOD &= 0xF0;		//设置定时器模式
	TL0 = 0xB0;		//设置定时初值
	TH0 = 0x3C;		//设置定时初值
	TF0 = 0;		//清除TF0标志
	TR0 = 1;		//定时器0开始计时
	
	ET0 = 1;
	EA = 1;
}

iic.h

#ifndef _IIC_H
#define _IIC_H

#include <STC15F2K60S2.H>
#include "intrins.h"

sbit SDA = P2^1;
sbit SCL = P2^0;

void IIC_Start(void); 
void IIC_Stop(void);  
bit IIC_WaitAck(void);  
void IIC_SendAck(bit ackbit); 
void IIC_SendByte(unsigned char byt); 
unsigned char IIC_RecByte(void); 

#endif

iic.c

#include "iic.h"

#define DELAY_TIME 5

//I2C总线内部延时函数
void IIC_Delay(unsigned char i)
{
    do{_nop_();}
    while(i--);        
}

//I2C总线启动信号
void IIC_Start(void)
{
    SDA = 1;
    SCL = 1;
    IIC_Delay(DELAY_TIME);
    SDA = 0;
    IIC_Delay(DELAY_TIME);
    SCL = 0;	
}

//I2C总线停止信号
void IIC_Stop(void)
{
    SDA = 0;
    SCL = 1;
    IIC_Delay(DELAY_TIME);
    SDA = 1;
    IIC_Delay(DELAY_TIME);
}

//发送应答或非应答信号
void IIC_SendAck(bit ackbit)
{
    SCL = 0;
    SDA = ackbit;  					
    IIC_Delay(DELAY_TIME);
    SCL = 1;
    IIC_Delay(DELAY_TIME);
    SCL = 0; 
    SDA = 1;
    IIC_Delay(DELAY_TIME);
}

//等待应答
bit IIC_WaitAck(void)
{
    bit ackbit;
	
    SCL  = 1;
    IIC_Delay(DELAY_TIME);
    ackbit = SDA;
    SCL = 0;
    IIC_Delay(DELAY_TIME);
    return ackbit;
}

//I2C总线发送一个字节数据
void IIC_SendByte(unsigned char byt)
{
    unsigned char i;

    for(i=0; i<8; i++)
    {
        SCL  = 0;
        IIC_Delay(DELAY_TIME);
        if(byt & 0x80) SDA  = 1;
        else SDA  = 0;
        IIC_Delay(DELAY_TIME);
        SCL = 1;
        byt <<= 1;
        IIC_Delay(DELAY_TIME);
    }
    SCL  = 0;  
}

//I2C总线接收一个字节数据
unsigned char IIC_RecByte(void)
{
    unsigned char i, da;
    for(i=0; i<8; i++)
    {   
    	SCL = 1;
	IIC_Delay(DELAY_TIME);
	da <<= 1;
	if(SDA) da |= 1;
	SCL = 0;
	IIC_Delay(DELAY_TIME);
    }
    return da;    
}