PWM呼吸灯

##单个定时器

#include <reg52.h>
#include <intrins.h>

unsigned char PWM_COUNT;    //计数
unsigned int HUXI_COUNT;    //占空比更新时间
unsigned char PWM_VLAUE;    //占空比比对值
bit direc_flag;							//占空比更新方向


void Enable_138(unsigned char ch)
{
	P2 = (P2 & 0x1f ) | (ch << 5);
	_nop_();
	_nop_();
	P2 &= 0x1f;
}


void timer0_init()
{
    TMOD=0x02;          //模式设置，定时器0，工作于模式2（M1=1，M0=0）
    TH0=0x47;               //定时器溢出值设置，每隔200us发起一次中断。
    TL0=0X47;
    TR0=1;                  //定时器0开始计时
    ET0=1;                  //开定时器0中断
    EA=1;                       //开总中断
    PWM_COUNT =0;
}
void time0() interrupt 1
{   

    PWM_COUNT++;
    HUXI_COUNT++;
    if(PWM_COUNT == PWM_VLAUE)      //判断是否到了点亮LED的时候
		{
			P0 = 0xef;
			Enable_138(4);
		}																	//点亮LED
    if(PWM_COUNT == 10)             //当前周期结束
    {
        P0 = 0xff;
				Enable_138(4);			//熄灭LED
        PWM_COUNT = 0;              //重新计时
    }
    if((HUXI_COUNT == 600) && (direc_flag == 0))
    {                               //占空比增加10%
        HUXI_COUNT = 0;
        PWM_VLAUE++;
        if(PWM_VLAUE == 9)          //占空比更改方向
            direc_flag = 1; 
    }
    if((HUXI_COUNT == 600) && (direc_flag == 1))
    {                               //占空比减少10%
        HUXI_COUNT = 0;
        PWM_VLAUE--;
        if(PWM_VLAUE == 1)          //占空比更改方向
            direc_flag = 0; 
    }   
}
void main()
{
		P0 = 0x00;
		Enable_138(5);
		P0 = 0x00;
		Enable_138(6);
    HUXI_COUNT = 0;
    PWM_COUNT = 0;
    PWM_VLAUE = 5;
    direc_flag = 0;
	
    P0 = 0xff;           
		Enable_138(4);
    timer0_init();      //定时器0初始化
    while(1);
}