原理图.png

代码如下：

#include<reg52.h>
#define uint unsigned int 
#define uchar unsigned char                          
uchar time; 
double count=26;    //?????,???????26%
sbit PWM=P0^2;      //P2^0???PWM 
sbit key_add=P3^2;   //??????? ?I/O?
sbit key_dec=P3^3;   //??????? ?I/O?
/************????**************/
void delayxms(uint z); //??
void Motor_add();     //????,??????
void Motor_dec();      //????,??????
void timer0_init();     //???0???
/*********???********************/
void main()
{    
    timer0_init();
    delayxms(5);
    while(1)
    {
     Motor_add();
     Motor_dec();
    }
}

/****************????**********************/
void delayxms(uint z) //??xms??
{
    uint x,y;
    for(y=z;x>0;x--)
        for(y=110;y>0;y--);
}
void Motor_add()  //????
{
  if(key_add==0)
  {
      delayxms(2); //????????,??????????
  if(key_add==0)
  {
      count+=0.5;   //????????????0.5
   if(count>=32)        //???????
    {
    count=32;
    }
  }
    while(!key_add);
  }
}


void Motor_dec()//????
{
 if(key_dec==0)
 {
  delayxms(2);//????????,??????????
  if(key_dec==0)
  {
    count-=0.5;     //????????????0.5
   if(count<=25)    //???????
   {
    count=25;
   }
  }
    while(!key_dec);
   }

}

/***********???0???***********/

void timer0_init()

{

  TMOD=0x01; //???0?????1
  TH0=(65536-10)/256;
  TL0=(65536-10)%256;
  TR0=1;
  ET0=1;
  EA=1;
} 
/**************??0????******************/

void timer0_int() interrupt 1 

{

    

  TR0=0;    //?????????,?????
  TH0=(65536-10)/256;
  TL0=(65536-10)%256;
  TR0=1;
  time++;
  if(time<count)      //count????
  {

    PWM=1;     
  }

  else 
    PWM=0;  
  if(time>=100)
  {
    time=0;
  }
 }