PWM and serial communication based on 51 single chip microcomputer

This example sets up a button to adjust the square wave of different frequencies (multiples of 100) from 100-1000hz. In addition, serial port communication is added, and the corresponding frequency can be set through the numbers sent by the serial port;

#include  

#include "uart.h"  

sbit PWMOUT = P1^0;  

sbit led = P2^2;  

sbit KEY1 = P1^2;  

sbit KEY2 = P3^3;  

unsigned char HighRH = 0; //high byte of high level reload value  

unsigned char HighRL = 0; //low byte of high level reload value  

unsigned char LowRH = 0; //high byte of low level reload value  

unsigned char LowRL = 0; //low byte of low level reload value  

unsigned int fr;  

unsigned int k=0,t,i;  

unsigned int s = 100;  

unsigned char a[3];  

unsigned int b=0;  

void ConfigPWM(unsigned int fr, unsigned char dc);  

void ConfigUART(unsigned int baud);  

void delay(unsigned int n){ while (n--);}  

void main()  

{     

    bit backup1 = 1;  

    bit backup2 = 1;  

    bit keybuf1 = 1; // Temporary storage of key values, temporarily saving the scanned values ​​of keys  

    bit keybuf2 = 1; // Temporary storage of key values, temporarily saving the scanned values ​​of keys  

    //keybuf1 = KEY1; //temporarily save the current scan value  

    EA=1;  

    led = 0;  

    ConfigUART(9600); //Configure the baud rate to 9600  

    ConfigPWM(100,50);  

    //Timer1Init();  

    while (1)  

    {  

      if(k==1)  

      {  

          k=0;  

          ConfigPWM(s,50);  

          led = ~led;delay(2000);  

      }  

            keybuf1 = KEY1; //temporarily store the current scan value  

          if (keybuf1 != backup1) //The current value is not equal to the previous value, indicating that the key is in action  

          {   

            delay(1000); //delay about 10ms  

            if (keybuf1 == KEY1) //Judge whether the scan value has changed, i.e. the key is jittering  

            {  

               if (backup1 == 0) //If the previous value is 0, it means the current action is a pop-up  

                  {  

                    s = s-50;        

                }  

                backup1 = keybuf1; //Update the backup to the current value for the next comparison  

            }  

            ConfigPWM(s,50);  

          }  

          keybuf2 = KEY2; //temporarily store the current scan value  

          if (keybuf2 != backup2) //The current value is not equal to the previous value, indicating that the key is in action  

          {  

            delay(1000); //delay about 10ms  

            if (keybuf2 == KEY2) //Judge whether the scan value has changed, that is, the key is jittering  

            {  

                if (backup2 == 0) //If the previous value is 0, it means the current action is a pop-up  

                {  

                    s = s+50;        

                }  

                backup2 = keybuf2; //Update the backup to the current value for the next comparison  

            }  

            ConfigPWM(s,50);  

          }  

    }  

}  

void ConfigUART(unsigned int baud)  

{  

    SCON = 0x50; //Configure the serial port to mode 1  

    TMOD &= 0x0F; // Clear the control bit of T1  

    TMOD |= 0x20; //Configure T1 to mode 2  

    TH1 = 256 - (11059200/12/32)/baud; //Calculate T1 reload value  

    TL1 = TH1; //initial value equals reload value  

    ET1 = 0; //Interrupt T1  

    ES = 1; //Serial port interrupt  

    TR1 = 1; //Start T1  

}  

void ConfigPWM(unsigned int fr, unsigned char dc)  

{  

unsigned int high, low;  

unsigned long tmp;  

tmp = (11059200/12)/fr; //Calculate the count value required for one cycle  

high = (tmp*dc) / 100; //Calculate the count value required for the high level  

low = tmp - high; //Calculate the count value required for the low level  

high = 65536 - high + 12; //Calculate the high level reload value and compensate for interrupt delay  

low = 65536 - low + 12; //Calculate the low level reload value and compensate for interrupt delay  

HighRH = (unsigned char)(high>>8); //Split the high-level reload value into high and low bytes  

HighRL = (unsigned char)high;  

LowRH = (unsigned char)(low>>8); // split the low level reload value into high and low bytes  

LowRL = (unsigned char)low;  

TMOD &= 0xF0; // Clear the control bit of T0  

TMOD |= 0x01; //Configure T0 to mode 1  

TH0 = HighRH; //Load T0 reload value  

TL0 = HighRL;  

ET0 = 1; // Enable T0 interrupt  

TR0 = 1; //Start T0  

PWMOUT = 1; //output high level  

}  

void InterruptTimer0() interrupt 1  

{  

    if (PWMOUT == 1) //When the current output is high, load the low level value and output low level  

    {  

        TH0 = LowRH;  

        TL0 = LowRL;  

        PWMOUT = 0;  

    }  

    else //When the current output is low level, load the high level value and output high level  

    {  

        TH0 = HighRH;  

        TL0 = HighRL;  

        PWMOUT = 1;  

    }  

}  

/*void Timer1Init() 

{ 

    TMOD|=0X10; //Select timer 1 mode, working mode 1, only use TR1 to start. 

    TH1=0XFC; //Assign initial value to the timer, set the timer to 1ms 

    TL1=0X18;    

    ET1=1; //Enable timer 1 interrupt 

    EA=1; //Open the general interrupt 

    TR1=1; //Turn on the timer            

} 

void Timer1() interrupt 3 

{ 

    static u16; 

    TH1=0XFC; //Assign initial value to the timer, set the timer to 1ms 

    TL1=0X18; 

    i++; 

    if(i==1000) 

    { 

        i=0; 

        t++; 

        if(t%2==0) 

        { 

           SBUF=t/10; 

           SBUF=t%10; 

        } 

    }    

}*/  

void ComINT() interrupt 4 //interrupt receiving program  

{     

    if(RI) //Judge whether the reception is complete. After the reception is completed, the hardware sets the RI bit  

    {  

      RI=0;                                    

      //SBUF=SBUF;  

      a[b]=SBUF;  

      b++;  

       if(b==3)  

       {  

         /*if(a[0]=='a'&&a[1]=='b'&&a[2]=='c')  

         {led = 0; delay(2000);} 

         else 

         {led = 1;}*/  

         b=0;s=(a[0]-0x30)*100+(a[1]-0x30)*10+(a[2]-0x30);  

          k=1;  

          //SBUF = 'T';  

       }    

}       

if(TI)  

{  

      TI=0;  

    }  

}