51 MCU PWM duty cycle adjustment

//(Tested, note: AT89S51 MCU, some MCU P3_7 needs to be changed to P3^7)

/****************************************************** ******************************
* Program name: PWM duty cycle adjustment demonstration program *
*Procedure description: *
* Only 4 buttons are needed. *
* Regarding the determination of frequency and duty cycle, for a 12M crystal oscillator, the output frequency is 1KHZ, so the number of timer interrupts is set to *
*10, that is, 0.01MS interruption, then TH0=FF, TL0=F6; since the interruption time is set to 0.01ms, you can set *
*The duty cycle can be changed from 1-99%. That is, 0.01ms*100=1ms *
*************************************************** ****************************/

#include
#define uchar unsigned char
#define uint unsigned int
uchar timer0_tick,ZKB=1; //timer0_tick count, ZKB duty cycle
uchar i=0,n=0,temp=0;
code seven_seg[10]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90};//1,2,3, 4, 5, 6, 7, 8, 9
code scan[2]={0xfd,0xfe};
uchar counter[2]={0,0};
sbit AN1=P3^2; //Adjust the unit digit
sbit AN2=P3^3; //Adjust the tens digit
sbit AN3=P3^4; //Start button
sbit AN4=P3^5; //Confirm button
void delay(uint z) //software delay function
{
   uint x,y;
   for(x=z;x>0;x--)
   for(y=110;y>0;y--);
}
static void timer0_isr(void) interrupt 1 using 0 //interrupt function
{
   TR0=0;
   TL0=0xf6;
   TH0=0xff;
   TR0=1;
   if (ZKB>99) ZKB=1;
    if (ZKB<1) ZKB=99;
   counter[0]=ZKB%10;
   counter[1]=ZKB/10;
   n++;
   if(n==100)
    {
     n=0;
     i++;
     if(i==2) i=0;
     P0=seven_seg[counter[i]];
     P2=scan[i];
    }
   timer0_tick++;
   if(timer0_tick++==100)
    {
     timer0_tick=0;
  
    }
     if(AN2==0)
    {
     delay(100);
     if(AN2==0)
      {
       temp=1;
       counter[0]++;
       if(counter[0]==10)
        {
         counter[0]=0;
        }

      }
    }
   if(AN1==0)
    {
     delay(100);
     if(AN1==0)
      {
       temp=1;
       counter[1]++;
       if(counter[1]==10)
        {
         counter[1]=0;
        }

      }
      }
ZKB=counter[0]+counter[1]*10;
if(AN4==0)
   {
    delay(5);
    if(AN4==0)
    temp=0;
   }
if(temp==1)
P3_7=0; // P3_7 is the pulse output pin
else
   {
    if (timer0_tick<=ZKB) /*When it is less than the duty cycle value, it outputs a low level, and when it is higher, it outputs a high level, thereby adjusting the duty cycle*/
        {
      P3_7=1;
     }
       else
        {
     P3_7=0;
     }

   }
}
static void timer0_initialize(void) //Interrupt initialization
{
   EA=0;
   timer0_tick=0;
   TR0=0;
   TMOD=0x01;
   TL0=0xf6;
   TH0=0xff;
   PT0=0;
   ET0=1;
   TR0=1;
   EA=1;
}
void main(void)
{
   STAR: delay(100);
     if(AN3!=0) goto STAR; //Press key 3 to start pulse
     timer0_initialize();
     while(1);
}
// Press button 3 to start the pulse generator. The initial duty cycle is set to 1%. Press button 1 to adjust the tens digit.
// Press key 2 to adjust the unit digit. Once adjusted, the output is 0. You must press the confirmation key to confirm.
//Output correct pulse. The duty cycle can be adjusted arbitrarily from 1 to 99%.