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51单片机 – PWM控制P0口Led呼吸灯

51单片机 342浏览 0评论

通过IO口模拟产生PWM,并通过占空比的控制Led灯的亮度。定时器0用来产生PWM,定时器1用来调整占空比的数值。

代码已经在KST-51 v1.3.2开发板验证通过。

效果展示:

#include <reg52.h>

sbit ADDR0 = P1^0;
sbit ADDR1 = P1^1;
sbit ADDR2 = P1^2;
sbit ADDR3 = P1^3;
sbit ENLED = P1^4;

unsigned long periodCnt = 0;
unsigned char highRH = 0;                       //高电平重载值的高字节
unsigned char highRL = 0;                       //高电平重载值的低字节
unsigned char lowRH = 0;                        //低电平重载值的高字节
unsigned char lowRL = 0;                        //低电平重载值的低字节
unsigned char T1RH = 0;
unsigned char T1RL = 0;

void ConfigPWM(unsigned int freq, unsigned char dutyCycle);
void ConfigTimer1(unsigned int ms);
void AdjustDutyCycle(unsigned char dutyCycle);

void main()
{
EA = 1;                                         //开总中断
    ENLED = 0;
    ADDR3 = 1;
    ADDR2 = 1;
    ADDR1 = 1;
    ADDR0 = 0;

    ConfigPWM(100, 10);                         //配置并启动PWM
    ConfigTimer1(100);                          //用Timer1定时调整占空比

    while (1);
}

void ConfigPWM(unsigned int freq, unsigned char dutyCycle)
{
    unsigned int high, low;

    periodCnt = 11059200 / 12 / freq;           //计算一个周期所需的计数值
    high = (periodCnt * dutyCycle) / 100;       //计算高电平所需的计数值
    low = periodCnt - high;                     //计算低电平所需的计数值
    high = 65536 - high + 12;                   //计算高电平的定时器重载值并补偿中断延时
    low = 65536 - low + 12;                     //计算低电平的定时器重载值并补偿中断延时
    highRH = (unsigned char)(high >> 8);        //高电平重载值拆分为高低字节
    highRL = (unsigned char)high;
    lowRH = (unsigned char)(low >> 8);          //低电平重载值拆分为高低字节
    lowRL = (unsigned char)low;
    TMOD &= 0xF0;                               //清零Timer0的控制位
    TMOD |= 0x01;                               //配置Timer0为模式1
    TH0 = highRH;                               //加载Timer0重载值
    TL0 = highRL;
    ET0 = 1;                                    //使能Timer0中断
    TR0 = 1;                                    //启动Timer0
    P0 = 0xFF;                                  //P0口全部输出高电平
}

void ConfigTimer1(unsigned int ms)
{
    unsigned long temp;

    temp = 11059200 / 12;                       //定时器计数频率
    temp = (temp * ms) / 1000;                  //计算所需的计数值
    temp = 65536 - temp + 12;                   //计算定时器重载值
    T1RH = (unsigned char)(temp >> 8);          //定时器重载值拆分为高低字节
    T1RL = (unsigned char)temp;
    TMOD &= 0x0F;                               //清零Timer1的控制位
    TMOD |= 0x10;                               //配置Timer1为模式1
    TH1 = T1RH;                                 //加载Timer1重载值
    TL1 = T1RL;
    ET1 = 1;                                    //使能Timer1中断
    TR1 = 1;                                    //启动Timer1
}

void AdjustDutyCycle(unsigned char dutyCycle)
{
    unsigned int high, low;

    high = (periodCnt * dutyCycle) / 100;
    low = periodCnt - high;
    high = 65536 - high + 12;
    low = 65536 - low + 12;
    highRH = (unsigned char)(high >> 8);
    highRL = (unsigned char)high;
    lowRH = (unsigned char)(low >> 8);
    lowRL = (unsigned char)low;
}
void InterruptTimer0() interrupt 1
{
    if (P0 == 0xFF)                             //当前P0口输出为高电平时,装载低电平值并输出低电平
    {
        TH0 = lowRH;
        TL0 = lowRL;
        P0 = 0x00;
    }
    else if (P0 == 0x00)                        //当前P0口输出为低电平时,装载高电平值并输出高电平
    {
        TH0 = highRH;
        TL0 = highRL;
        P0 = 0xFF;
    }
}

void InterruptTimer1() interrupt 3
{
    static bit dir = 1;
    static signed char index = 0;
    unsigned char code table[19] = {
        5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95
    };
    
    TH1 = T1RH;
    TL1 = T1RL;

    AdjustDutyCycle(table[index]);
    if (dir)
    {
        index++;
        if (index >= 18)
        {
            dir = 0;
        }
    }
    else
    {
        index--;
        if (index <= 0)
        {
            dir = 1;
        }
    }
}

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