51 single chip microcomputer drives servo motor program

Except for a few enhanced versions of 51 microcontrollers, many do not have PWM. Therefore, to control servo motors with 51, software simulation of PWM is often required. I have seen some codes that output PWM waves through delay, and some use timers, but those codes are more troublesome to drive multi-channel servo circuits. The following code generates a reminder every 0.5ms through timer 0. The program can return the value to the servo motor signal pin by calling the DJ() function in the large loop. The DJ() function can determine the rotation angle, but because the timer is set to a 0.5ms interrupt, this determines that the rotation angle can only be -45, -90, 0, 45, 90. If you want to improve the accuracy, you need to set the initial value of the timer and change the num value of the function to achieve it.
#include"reg52.h"
unsigned int num=0;
//Servo
sbit DJ1=P3^6;
sbit DJ2=P3^7; /*Pin definition*/
int DJ(int a); //Function declaration
timerinit() //Timer interrupt initialization
 {
 TMOD=0x01; //Set timer 0 to working mode 1
 EA=1; //Open total interrupt
 ET0=1; //Timer 0 interrupt enable
    TH0 = (65536-500)/256; //The initial value makes the timer overflow in 0.5 milliseconds
    TL0 = (65536-500)%256;
 TR0=0;         
 }
main()
 {
 timerinit();
 while(1)
  {
    }
 }
timer() interrupt 0 //An interrupt occurs every 0.5ms. After 20ms, the timer is reset to 0 and counts again
 {
  num++;
  DJ1=DJ(3);
  DJ2=DJ(3);
  if(num>=40)     
  {
   num=0;
      TH0 = (65536-500)/256; //The initial value makes the timer overflow in 0.5 milliseconds
    TL0 = (65536-500)%256;
   return;
  }
 }
int DJ(char a) //When a=3, the position of the servo is 0 degrees, a=2, a=1 respectively correspond to -45 -90 degrees, a=4, a=5 correspond to 45 90 degrees
 {
 if(num>=a||num>=5)
  return 0;
 if(num>=1)
  return 1;
 }
    Due to the time constraints, I have not tested the feasibility of the program (usually there is no problem, haha). If I have time, I will continue to improve the program and add the function of controlling the rotation speed of the servo. If you want to make a robot, you should get a professional driver board, so that debugging will be very intuitive and convenient, reducing many unnecessary troubles.