#单片机#利用pcf8591读取电位器电压值

sbit sda=P2^0;

sbit scl=P2^1;

#define uint unsigned int

#define uchar unsigned char

uchar code table[] ={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90,0xbf,0x40};

//0、1、2、3、4、5、6、7、8、9、A、b、C、d、E、F的显示码

//--定义PCF8591的读写地址--//

#define WRITEADDR 0x90 //写地址

#define READADDR 0x91 //读地址

void delayms(uint z)

{

int x,y;

for(x=z;x>0;x--)

for(y=110;y>0;y--);

}

void delay()

{ ;; }

void start()

{

sda=1;

delay();

scl=1;

delay();

sda=0;

delay();

}

void stop()

{

sda=0;

delay();

scl=1;

delay();

sda=1;

delay();

}

void respons() //应答

{

uchar i;

scl=1;

delay();

while((sda==1)&&(i<250))i ;

scl=0;

delay();

}

void write_byte(uchar date)

{

uchar i,temp;

temp=date;

for(i=0;i<8;i )

{

temp=temp<1;

scl=0;

delay();

sda=CY;

delay();

scl=1;

delay();

}

scl=0;

delay();

sda=1;

delay();

}

uchar read_byte()

{

uchar i,k;

scl=0;

delay();

sda=1;

delay();

for(i=0;i<8;i )

{

scl=1;

delay();

k=(k<1)|sda;

scl=0;

delay();

}

return k;

}

uchar ADC_PCF8591_rd_(uchar channal)

{

uchar date;

start();

write_byte(0x90);

respons();

write_byte(channal);

respons();

start();

write_byte(0x91);

respons();

date=read_byte();

stop();

return date;

}

void ADC_PCF8591_wt_(uchar date)

{

start();

write_byte(0x90);

respons();

write_byte(0x40);

respons();

write_byte(date);

respons();

stop();

}

//注:主函数中进行AD或者DA的选择，进行处理

void display(uchar i)

{

float a; int j;

a=i;

a=a*500/256;

j=a;

P2=0xfd;

P0=0xff;

P0=~table[j/100]&0x7f;

delayms(5);

P2=0xfb;

P0=0xff;

P0=~table[j0/10];

delayms(5);

P2=0xf7;

P0=0xff;

P0=~table[j];

delayms(5);

}

void main()

{

uint temp;

sda=1;

delay();

scl=1;

delay();

while(1)

{

temp=ADC_PCF8591_rd_(0x00);

display(temp);

}

}