pwm.c

AVR MEGA128单片机的PWM输出例子程序

//ICC-AVR application builder : 2008-3-25 0:28:31
// Target : M128
// Crystal: 11.059Mhz

#include <iom128v.h>
#include <macros.h>

void port_init(void)
{
 PORTA = 0xFF;
 DDRA  = 0x00;
 PORTB = 0xEF;
 DDRB  = 0x10;
 PORTC = 0xFF; //m103 output only
 DDRC  = 0x00;
 PORTD = 0xFF;
 DDRD  = 0x00;
 PORTE = 0xFF;
 DDRE  = 0x00;
 PORTF = 0xFF;
 DDRF  = 0x00;
 PORTG = 0x1F;
 DDRG  = 0x00;
}

//TIMER0 initialisation - prescale:1
// WGM: CTC
// desired value: 2MHz
// actual value:  1.843MHz (-8.5%)
void timer0_init(void)
{
  TCCR0 = 0x00; //stop
 ASSR  = 0x00; //set async mode
 TCNT0 = 0xFB; //set count
 OCR0  = 0x05;
 TCCR0 = 0x19; //start timer
}

#pragma interrupt_handler timer0_comp_isr:16
void timer0_comp_isr(void)
{
 //compare occured TCNT0=OCR0
}

#pragma interrupt_handler timer0_ovf_isr:17
void timer0_ovf_isr(void)
{
 TCNT0 = 0xFB; //reload counter value
}

//call this routine to initialise all peripherals
void init_devices(void)
{
 //stop errant interrupts until set up
 CLI(); //disable all interrupts
 XDIV  = 0x00; //xtal divider
 XMCRA = 0x00; //external memory
 port_init();
 timer0_init();

 MCUCR = 0x00;
 EICRA = 0x00; //extended ext ints
 EICRB = 0x00; //extended ext ints
 EIMSK = 0x00;
 TIMSK = 0x03; //timer interrupt sources
 ETIMSK = 0x00; //extended timer interrupt sources
 SEI(); //re-enable interrupts
 //all peripherals are now initialised
}

void main(void)
{
 init_devices();
 while(1)
 ;
}