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I'm trying to use PWM for an LED on an ATmega8, any pin of port B. Setting up timers has been a annoying, and I don't know what to do with my OCR1A. Here's my code, and I'd love some feedback. I'm just trying to figure out how use PWM. I know the concept, and OCR1A is supposed to be the fraction of the whole counter time I want the pulse on. #define F_CPU 1000000 // 1 MHz #include <avr/io.h> #include <avr/delay.h> #include <avr/interrupt.h> int main(void){ TCCR1A |= (1 << CS10) | (1 << CS12) | (1 << CS11); OCR1A = 0x0000; TCCR1A |= ( 0 << WGM11 ) | ( 1 << WGM10 ) | (WGM12 << 1) | (WGM13 << 0); TCCR1A |= ( 1 << COM1A0 ) | ( 0 << COM1A1 ); TIMSK |= (1 << TOIE1); // Enable timer interrupt DDRB = 0xFF; sei(); // Enable global interrupts PORTB = 0b00000000; while(1) { OCR1A = 0x00FF; //I'm trying to get the timer to alternate being on for 100% of the time, _delay_ms(200); OCR1A = 0x0066; // Then 50% _delay_ms(200); OCR1A = 0x0000; // Then 0% _delay_ms(200); } } ISR (TIMER1_COMA_vect) // timer0 overflow interrupt { PORTB =~ PORTB; }

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