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发表于 2010-10-7 15:45:17
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#include "reg52.h"
#include "MacroAndConst.h"
#define LED P0 //定义LED接口
#define LED_ON() LED = 0x00 ; //所有LED亮
#define LED_OFF() LED = 0xff ; //所有LED熄灭
#define LED_PWM_LIMIT_MAX 99
#define LED_PWM_LIMIT_MIN 0
static uint8 s_u8TimeCounter = 0 ; //中断计数
static uint8 s_u8LedDirection = 0 ; //LED方向控制 0 :渐亮 1 :渐灭
static int8 s_s8LedPWMCounter = 0 ; //LED占空比
void Timer0Init(void)
{
TMOD &= 0xf0 ;
TMOD |= 0x01 ; //定时器0工作方式1
TH0 = 0xff ; //定时器初始值(200us中断一次)
TL0 = 0x47 ;
TR0 = 1 ;
ET0 = 1 ;
}
void Time0Isr(void) interrupt 1
{
static int8 s_s8PWMCounter = 0 ;
TH0 = 0xff ; //定时器重新赋初值
TL0 = 0x47 ;
if(++s_u8TimeCounter >= 100) //每20MS调整一下LED的占空比
{
s_u8TimeCounter = 0 ;
//如果是渐亮方向变化,则占空比递增
if((s_s8LedPWMCounter <= LED_PWM_LIMIT_MAX) &&(0 == s_u8LedDirection))
{
s_s8LedPWMCounter++ ;
if(s_s8LedPWMCounter > LED_PWM_LIMIT_MAX)
{
s_u8LedDirection = 1 ;
s_s8LedPWMCounter = LED_PWM_LIMIT_MAX ;
}
}
//如果是渐暗方向变化,则占空比递渐
if((s_s8LedPWMCounter >= LED_PWM_LIMIT_MIN) &&(1 == s_u8LedDirection))
{
s_s8LedPWMCounter-- ;
if(s_s8LedPWMCounter < LED_PWM_LIMIT_MIN)
{
s_u8LedDirection = 0 ;
s_s8LedPWMCounter = LED_PWM_LIMIT_MIN ;
}
}
s_s8PWMCounter = s_s8LedPWMCounter ; //获取LED的占空比
}
if(s_s8PWMCounter > 0) //占空比大于0,则点亮LED,否则熄灭LED
{
LED_ON() ;
s_s8PWMCounter-- ;
}
else
{
LED_OFF();
}
} |
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