程序是在51hei單片機(jī)開發(fā)板上面做的，燈接在P0^0上，程序可以通用，到你自己的開發(fā)板或者是自己搭的電路也行.
/**
******************************************************************************
*file : main.c
*author : xr
*date : 2014年4月15日17:38:07 - 2014年4月15日 18:47:29
*version : V1.2.3
*brief : PWM應(yīng)用-控制小燈的亮度-實(shí)現(xiàn)傳說中的呼吸燈效果 單片機(jī)STC89C52RC MCU 晶振 11.0592MHZ
******************************************************************************
*/
#include <reg52.h>
sbit ADDR0 = P1^0; //如果是自己搭的電路，可以無視下面這幾行
sbit ADDR1 = P1^1;
sbit ADDR2 = P1^2;
sbit ADDR3 = P1^3;
sbit ENLED = P1^4;
sbit PWMOUTLED = P0^0;//用于PWM控制輸出
unsigned char heighHR0, heighLR0;//PWM一個(gè)周期中高電平高字節(jié)和低字節(jié)重載值
unsigned char lowHR0, lowLR0;//PWM一個(gè)機(jī)器周期中低電平時(shí)高字節(jié)和低字節(jié)重載值
void Initial();
void ConfigPWM(unsigned int fr, unsigned char dc);
void ClosePWM();
void main(void)
{
unsigned int i;
Initial();
while (1) //呼吸燈效果
{
//LED亮->暗
ConfigPWM(100, 10);//配置PWM頻率為100HZ,占空比為10%
for (i = 0; i < 30000; i++); //軟件測試延時(shí)大約76ms
ConfigPWM(100, 20);//配置PWM頻率為100HZ,占空比為20%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 30);//配置PWM頻率為100HZ,占空比為30%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 40);//配置PWM頻率為100HZ,占空比為40%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 50);//配置PWM頻率為100HZ,占空比為50%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 60);//配置PWM頻率為100HZ,占空比為60%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 70);//配置PWM頻率為100HZ,占空比為70%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 80);//配置PWM頻率為100HZ,占空比為80%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 90);//配置PWM頻率為100HZ,占空比為90%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 95);//配置PWM頻率為100HZ,占空比為95%
for (i = 0; i < 30000; i++);
//LED暗->亮
ConfigPWM(100, 90);//配置PWM頻率為100HZ,占空比為10%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 80);//配置PWM頻率為100HZ,占空比為20%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 70);//配置PWM頻率為100HZ,占空比為30%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 60);//配置PWM頻率為100HZ,占空比為40%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 50);//配置PWM頻率為100HZ,占空比為50%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 40);//配置PWM頻率為100HZ,占空比為60%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 30);//配置PWM頻率為100HZ,占空比為70%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 20);//配置PWM頻率為100HZ,占空比為80%
for (i = 0; i < 30000; i++);
ConfigPWM(100, 10);//配置PWM頻率為100HZ,占空比為90%
for (i = 0; i < 30000; i++);
ClosePWM();
}
}
/*初始化*/
void Initial()
{
ADDR3 = 1;
ENLED = 0;//選擇U3，即LED
ADDR2 = 1;
ADDR1 = 1;
ADDR0 = 0;//LEDS6=0
}
/*使用T0配置PWM高低電平的頻率*/
void ConfigPWM(unsigned int fr, unsigned char dc) //fr為PWM的頻率，100HZ無閃爍，dc是PWM的占空比(高電平占的百分比)
{
unsigned long tmp;
unsigned int heigh, low;
tmp = 11059200/12;//一個(gè)機(jī)器周期頻率
tmp = tmp / fr; //一個(gè)機(jī)器周期中fr的頻率所需計(jì)數(shù)值(包括高電平和低電平)
heigh = (tmp * dc) / 100;//高電平占dc%，所需計(jì)數(shù)值
low = tmp - heigh;//低電平所需計(jì)數(shù)值
heigh = 65536-heigh;//高電平計(jì)數(shù)初值
low = 65536-low;//低電平計(jì)數(shù)初值
heighHR0 = (unsigned char)(heigh >> 8);//高電平裝入初值的高字節(jié)
heighLR0 = (unsigned char)heigh; //高電平裝入初值的低字節(jié)
lowHR0 = (unsigned char)(low >> 8); //低電平裝入初值的高字節(jié)
lowLR0 = (unsigned char)low; //低電平裝入初值的低字節(jié)
TMOD &= 0xF0;//清零T0控制位
TMOD |= 0x01;//設(shè)定T0工作方式1,16位可設(shè)定時(shí)器
TH0 = heighHR0;
TL0 = heighLR0;//裝入高電平計(jì)數(shù)初值
PWMOUTLED = 1;//開始時(shí)PWM輸出高電平
TR0 = 1;
ET0 = 1;
EA = 1;
}
/*關(guān)閉PWM*/
void ClosePWM()
{
TR0 = 0;//關(guān)閉Timer0
ET0 = 0;//關(guān)閉T0中斷
PWMOUTLED = 1;//PWM輸出高電平
}
/*定時(shí)器T0中斷服務(wù)*/
void Timer0_ISP() interrupt 1
{
//判斷PWM現(xiàn)在輸出的是高電平還是低電平
if (PWMOUTLED)
{
TH0 = lowHR0;
TL0 = lowLR0;//裝載低電平計(jì)數(shù)初值
PWMOUTLED = 0;//PWM輸出低電平
}
else
{
TH0 = heighHR0;
TL0 = heighLR0;//重裝裝載高電平計(jì)數(shù)初值
PWMOUTLED = 1;//PWM輸出高電平
}
}