yykk_006.c

一个用AVR单片机的定时器实现PWM功能的程序

//ICC-AVR application builder : 2006-11-25 0:15:12
// Target : M16
// Crystal: 7.3728Mhz

#include 
#include 

void port_init(void)
{
 PORTA = 0x00;
 DDRA  = 0x00;
 DDRB  = 0x08; //PB3为PWM输出，非常重要，否则无法输出波形
 DDRB  = 0x00;
 PORTC = 0x00; //m103 output only
 DDRC  = 0x00;
 PORTD = 0x00;
 DDRD  = 0x00;
}

//TIMER0 initialize - prescale:64
// WGM: Normal
// desired value: 1KHz
// actual value:  1.002KHz (0.2%)
void timer0_init(void)
{
 TCCR0 = 0x00; //stop
 TCNT0 = 0x8D; //set count /*TCNT0*/
 OCR0  = 0x73;  //set compare /*OCR0*/
 TCCR0 = 0x23; //start timer /*TCCR0*/
}

#pragma interrupt_handler timer0_comp_isr:20
void timer0_comp_isr(void)
{
 //compare occured TCNT0=OCR0
}

#pragma interrupt_handler timer0_ovf_isr:10
void timer0_ovf_isr(void)
{
 TCNT0 = 0x8D; //reload counter value
}

//call this routine to initialize all peripherals
void init_devices(void)
{
 //stop errant interrupts until set up
 CLI(); //disable all interrupts
 port_init();
 timer0_init();

 MCUCR = 0x00;
 GICR  = 0x00;
 TIMSK = 0x03; //timer interrupt sources /*TIMSK*/
 SEI(); //re-enable interrupts
 //all peripherals are now initialized
}

void main(void) /*加上这些，程序就可以运行了。*/
{
 init_devices();
 while(1)
 ;
}