51 MCU - potentiometer control servo

1. Question requirements

In order to make the ADC knowledge cooperate with other modules to realize different functions, here we plan to control the position of the servo propeller by twisting the potentiometer (sliding resistor). If we twist the potentiometer clockwise, the servo propeller will also rotate from one end to the other.

2.main.c test code

#include

#include //See Chapter 6, Lecture 8 for details

#include //See Chapter 8, Lecture 11 for details

#include //See Chapter 11, Lecture 3 for details

#include //See Chapter 14 for details

sbit PWMOUT=P1^7; //Servo signal line interface

u8 flag20ms = 0;

u8 PWM_VAL = 0;

void main()

{

    u8 val;

    u8 str[10];

    EA = 1;     

    InitLcd1602(); //Initialize LCD screen

    TIM1_Init(20000,6); //Timing 20ms, 6 is fine-tuning to make the timing more accurate

    TIM0_Init(100,9); //Timing 0.1ms, dedicated to servos, 9 is fine-tuning to make timing more accurate

    LcdShowStr(6, 0, "AIN0");

    while (1)

    {

        if (flag20ms) //Get the conversion value of ADC channel 0 every 20ms

        {

            flag20ms = 0;

            val = GetADCValue(0); //Get the conversion value of ADC channel 0   

            ValueToString(str, val); //Convert voltage value to string format

            LcdShowStr(6, 1, str); //Display the voltage of channel 0    

            PWM_VAL=val/14+5; //The value range of PWM_VAL is 5~23

        }

    }

}

void TIM0_IRQHandler() interrupt 1

{ 

    static u8 pwm=0;

    TH0 = T0RH; //Reload the reload value

    TL0 = T0RL;

    pwm++;

    if(pwm>=200)pwm=0; //pwm changes between 0~199 with an interval of 0.1ms and a period of 20ms

    if(pwm    else PWMOUT=0;

}

void TIM1_IRQHandler() interrupt 3

{  

    TH1 = T1RH; //Reload the reload value

    TL1 = T1RL;

    flag20ms = 1;

}

Let's plug back the jumper caps that we unplugged in the previous chapter to test AD and DA. There is a potentiometer in the middle of the bottom of the development board. You can use a flat-blade screwdriver to rotate the potentiometer and observe that the servo propeller rotates. In addition, it is best to use an external power supply for the servo. Using the development board to power the servo will cause the LCD screen to lose voltage and flicker, and the stability of the servo is not very good. When I tested it, I used another 5V power supply voltage to power the servo. The connection diagram is as follows