pwm.c

avr单片机PWM调制

#include <inttypes.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>

#include "iocompat.h"           

ISR (TIMER0_OVF_vect)          
{
    static uint16_t pwm;        
    static uint8_t direction=0;
    
	if(direction==0)
	 {
	   if(pwm<=250)
	     pwm*=1.10;
	   else
		 { direction=1;
		 }
	 }
	 if(direction==1)
	 {
	   if(pwm>=0)
	     pwm*=0.9;
	   else
		 direction=0;
	 }
    

     OCR1B=pwm;                  
}


//端口初始化 
void port_init(void) 
{ 
        PORTB = 0x00; 
        DDRB  = 0xFF; 
} 

//定时器T0初始化 
void timer0_init(void) 
{ 
      
	 TCCR0=0x06;//系统时钟64分频 8MHZ 每中断一次时间是 1/（8000000/64/(0xFF-0x06+1)）=1/500s
	 // TCCR0A=_BV(COM1B1)|_BV(COM1A1)|_BV(WGM10);
     // TCCR0B=_BV(CS11)|_BV(CS10);//时钟选择
	 TCNT0=0x06;
} 

void init_devices(void) 
{ 
        MCUCR  = 0x00; //电源管理控制，空闲模式
		GICR   = 0x00; //通用中断控制寄存器
        port_init(); 
        timer0_init(); 
        sei();//开全局中断 
} 

int main (void)
{

   init_devices(void) ;

    /* loop forever, the interrupts are doing the rest */

    while(1);

    return (0);
}