项目13—PCF8951与LCD1602实现电压表的设计（含PCF8951详细解释）

用PCF8951，AT89C51，滑动电阻POT—HG，显示器LCD1602，和排阻RESPACK—8。

PCF89C51：

PCF8591是一个单片集成、单独供电、低功耗、8-bit CMOS数据获取器件。PCF8591具有4个模拟输入、1个模拟输出和1个串行I²C总线接口。PCF8591的3个地址引脚A0, A1和A2可用于硬件地址编程，允许在同个I2C总线上接入8个PCF8591器件，而无需额外的硬件。在PCF8591器件上输入输出的地址、控制和数据信号都是通过双线双向I2C总线以串行的方式进行传输。

PCF8591的功能包括多路模拟输入、内置跟踪保持、8-bit模数转换和8-bit数模转换。PCF8591的最大转化速率由I2C总线的最大速率决定。

LCD1602在前文有所描述，这里不再一一解释。

仿真图如下：

程序如下： 

main.c

#include<reg51.h>
#include<lcd1602.c>
#include<pcf8591.c>
unsigned char cp,cp1,flash,ad0,ad1;
unsigned int year = 2020;
unsigned int v0,v1,v2,v3;
void timer_isr(void) interrupt 1
{TH0 = (65535 - 2000) / 256;TL0 = (65535 - 2000) % 256;cp++;cp1++;if(cp1 >= 250){goto_xy(1,0);display_string("v0:"); display_num(v0 / 100);display_string(".");display_num(v0 / 10 % 10);	display_num(v0 % 10);goto_xy(1,8);display_string("v1:"); display_num(v1 / 100);display_string(".");display_num(v1 / 10 % 10);	display_num(v1 % 10);	}
}
void timer_init(void)
{TMOD = 0x01;TH0 = (65535 - 2000) / 256;TL0 = (65535 - 2000) % 256;EA = 1;ET0 = 1;TR0 = 1;
}
void main(void)
{timer_init();lcd1602_init();lcd1602_clear();while(1){if(cp >= 250){cp = 0;ad0 = get_pcf8591_ADC(0);delay(30);	ad0 = get_pcf8591_ADC(0);delay(30);v0 = ad0 * 1.96;ad1 = get_pcf8591_ADC(1);delay(30);	ad1 = get_pcf8591_ADC(1);delay(30);v1 = ad1 * 1.96;}}
}

 LCD1602.c

#define uchar unsigned char 
#define uint  unsigned int
sbit RS = P2^4;//数据/命令
sbit RW = P2^5;//读/写
sbit E  = P2^6;//使能
uchar i;
void delay(unsigned int x)
{while(x--);
}
void write_command(uchar command)
{RW = 0;RS = 0;P0 = command;E = 1;delay(100);E = 0;RW = 1;
}
void write_data(uchar date)
{RW = 0;RS = 1;E = 1;P0 = date;delay(100);E = 0;RW = 1;
}
void lcd1602_init(void)
{write_command(0x38);write_command(0x0f);	write_command(0x0c);	write_command(0x06);
}
void lcd1602_clear(void)
{write_command(0x01);write_command(0x02);
}
void display_string(uchar *p)
{while(*p){write_data(*p);p++;	}
}
void display_num(uchar x)
{
双数字
//	write_data((x / 10) + 0x30);
//	write_data((x % 10) + 0x30);
//单数字write_data(x + 0x30);
}
void goto_xy(uchar x,uchar y)
{if(x == 1)write_command(0x80 + y);if(x == 2)write_command(0x80 + 0x40 + y);
}

 PCF8951.c

#include "intrins.h"
#define somenop Delay5us()
#define SlaveAddrW 0xA0
#define SlaveAddrR 0xA1
//总线引脚定义
sbit SDA_s = P3^7;  /* 数据线 */
sbit SCL_s = P3^6;  /* 时钟线 */
void Delay5us()		//@12.000MHz
{unsigned char i;_nop_();_nop_();i = 12;while (--i);
}
//总线启动条件
void IIC_Start(void)
{SDA_s = 1;SCL_s = 1;somenop;SDA_s = 0;somenop;SCL_s = 0;	
}//总线停止条件
void IIC_Stop(void)
{SDA_s = 0;SCL_s = 1;somenop;SDA_s = 1;
}//应答位控制
void IIC_Ack(bit ackbit)
{if(ackbit) {	SDA_s = 0;}else {SDA_s = 1;}somenop;SCL_s = 1;somenop;SCL_s = 0;SDA_s = 1; somenop;
}//等待应答
bit IIC_WaitAck(void)
{SDA_s = 1;somenop;SCL_s = 1;somenop;if(SDA_s)    {   SCL_s = 0;IIC_Stop();return 0;}else  { SCL_s = 0;return 1;}
}//通过I2C总线发送数据
void IIC_SendByte(unsigned char byt)
{unsigned char i;for(i=0;i<8;i++){   if(byt&0x80) {	SDA_s = 1;}else {SDA_s = 0;}somenop;SCL_s = 1;byt <<= 1;somenop;SCL_s = 0;}
}//从I2C总线上接收数据
unsigned char IIC_RecByte(void)
{unsigned char da;unsigned char i;for(i=0;i<8;i++){   SCL_s = 1;somenop;da <<= 1;if(SDA_s) da |= 0x01;SCL_s = 0;somenop;}return da;
}
int get_pcf8591_ADC(unsigned char x)
{unsigned char adc;IIC_Start();IIC_SendByte(0x90);IIC_WaitAck();IIC_SendByte(x);IIC_WaitAck();IIC_Start();IIC_SendByte(0x91);IIC_WaitAck();adc = IIC_RecByte();IIC_WaitAck();IIC_Ack(0);IIC_Stop();return(adc);
}
//void pcf8591_out(unsigned char x)
//{
//	IIC_Start();
//	IIC_SendByte(0x90);
//	IIC_WaitAck();	
//	IIC_SendByte(0x40);
//	IIC_WaitAck();
//	IIC_SendByte(x);
//	IIC_WaitAck();	
//}

运行结果如下：