51 MCU Timer 2 Capture Mode Pulse Frequency Measurement

The conventional method of measuring the frequency of pulses is to use two timers of the 51 single-chip microcomputer to measure, one timer for timing and one timer for counting. Is there a better way to meet the needs without using so much hardware and only use one timer? Of course, timer 2 has an input capture function. P1.1 is connected to an external pulse. When a pulse comes, timer 2 enters the interrupt service program and interrupts once. It also has a timing function. The following is the main program:

#include

#define uint unsigned int

#define uchar unsigned char

#define ulong unsigned long 

uint timer2_count;

uint cap_count;

uchar code dispbit[]={0x01,0x02,0x04,0x08,0x10,0x20,0x40,0x80}; // define bit selection starting from the second digit

uchar code dispcode[]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90,0xff,0xbf}; //define segment code

uchar dispbuf[8]={0,0,0,0,0,0,10,10}; //display buffer

uchar temp[8];

uchar dispcount;

uint x;

bit flag;

sbit L1 = P0^7;

//sbit L2 = P0^1;

sbit W1=P1^2;

sbit W2=P1^3;

sbit W3=P1^4;

sbit W4=P1^5;

sbit W5=P1^6;

sbit W6=P1^7;

void display_wei(uchar dipcount)

{

 switch (dipcount){

 case 0: W1=1;W2=W3=W4=W5=W6=0;

   break;

 case 1: {W2=1;W1=W3=W4=W5=W6=0;}

   break;

 case 2: {W3=1;W2=W1=W4=W5=W6=0;}

   break;

 case 3: {W4=1;W2=W3=W1=W5=W6=0;}

   break;

 case 5: {W5=1;W2=W3=W4=W1=W6=0;}

   break;

 case 6: {W6=1;W2=W3=W4=W5=W1=0;}

   break;

 }

}

void timer2_init()

{

 ET2=1; //Start timer 2

   T2CON=0X09; //Set T2 to capture mode, and generate an interrupt on the falling edge

   TH2=(65535-5000)/256;

   TL2=(65535-5000)%256;

   EA=1; //Enable interrupt

   TR2=1; //Start the counter

}

void main()

{

  timer2_init();

  while(1)

  {

   uchar i;

 if(flag==1)

 {

  flag=0;

  x=cap_count; //Frequency formula The number of pulses measured in one second

  //x= x*563;

  //x=x/10;

  for(i=0;i<8;i++)

  {

   temp[i]=0; // array clear

  }

  i=0;   

  //x=123456;

  while(x/10)

  {

   temp[i]=x%10;

   x=x/10;

   i++;

  }

  temp[i]=x;

  for(i=0;i<6;i++)

  {

   dispbuf[i]=temp[i]; //Display 6-digit frequency (cache)

  }

  cap_count=0;

  TR2=1; 

 }

  }

}

void timer2_interrupt(void) interrupt 5 using 1 //interrupt service routine

{

  if(EXF2) //Captured interrupt

  {

    //L1=!L1;

 cap_count++;

        EXF2=0;

  }

  if(TF2)

  {

    TH2=(65535-5000)/256;

   TL2=(65535-5000)%256;

 timer2_count++;

 if(timer2_count==400)

 {

  //L2=!L2;

  flag=1;

  timer2_count=0;

  TR2=0; //stop counting

    }

 TF2=0;

 P0=dispcode[dispbuf[dispcount]]; //display data

 //P1 = ((P1&0x02)|dispbit[dispcount+2]); //bit selection

 display_wei(dispcount);

 dispcount++;

 if(dispcount==6)

 {

  dispcount=0;

 }

  }

}