51 single chip microcomputer realizes breathing light

I. Overview

Use 51 single chip microcomputer to control LED to realize the gradual change process from dark to bright and then from bright to dark.

II. Procedure

#include <STC15F2K60S2.H>

#include "MacroAndConst.h"

sbit LED = P1^5;

#define LED_ON() LED = 0; //LED is on

#define LED_OFF() LED = 1; //LED off

#define LED_PWM_LIMIT_MAX 99

#define LED_PWM_LIMIT_MIN 0

static u8 s_u8TimeCounter = 0; //interrupt count

static u8 s_u8LedDirection = 0; //LED direction control 0: gradually brighten 1: gradually fade out

static u8 s_u8LedPWMCounter = 0; //LED duty cycle

void Timer0Init(void)

{

AUXR |= 0x80; //Timer clock 1T mode

TMOD &= 0xF0; //Set timer mode

TL0 = 0x5C; //Set the initial timing value

TH0 = 0xF7; //Set the initial value of timing

TF0 = 0; // Clear TF0 flag

TR0 = 1; //Timer 0 starts timing

ET0 = 1; // Enable timer 0 interrupt

}

void Timer0Isr(void) interrupt 1

{

static int8 s_u8PWMCounter = 0;

TH0 = 0xF7; //Timer initial value (200us interrupt once)

TL0 = 0x5C;

if(++s_u8TimeCounter >= 100) //Adjust LED duty cycle every 20ms

{

s_u8TimeCounter = 0;

//If the direction changes gradually, the duty cycle increases

if((s_u8LedPWMCounter <= LED_PWM_LIMIT_MAX)&&(s_u8LedDirection == 0))

{

s_u8LedPWMCounter++;

if(s_u8LedPWMCounter > LED_PWM_LIMIT_MAX)

{

s_u8LedDirection = 1;

s_u8LedPWMCounter = LED_PWM_LIMIT_MAX;

}

}

//If the direction changes gradually, the duty cycle decreases

if((s_u8LedPWMCounter > LED_PWM_LIMIT_MIN)&&(s_u8LedDirection == 1))    

             //There is a pit here. If you write it as ">=", you will not achieve the expected effect.

{

s_u8LedPWMCounter--;

if(s_u8LedPWMCounter <= LED_PWM_LIMIT_MIN)

{

s_u8LedDirection = 0;

s_u8LedPWMCounter = LED_PWM_LIMIT_MIN;

}

}

s_u8PWMCounter = s_u8LedPWMCounter; //Get the duty cycle of LED

}

if(s_u8PWMCounter > 0) //If the duty cycle is greater than 0, the LED will be on, otherwise it will be off

{

LED_ON();

s_u8PWMCounter--;

}

else

{

LED_OFF();

}

}