Dear friendly,

I am currently trying to dim LEDs by applying PWM on the LEDs' supply 
voltage.
My setup is:
- Atmega32U16
- usbasp Programmer (chinese)
- 16 MHz external crystal
- hfuse c9, lfuse 3f
- External interrupts on INT0, INT1, INT2
- Use of Timer0 for more sophisticated interrupt handling

Here's the relevant part of my init code (for whole main see bottom):

1

int main(void) {

2

    ...

3

4

    // use OC1B as output, Pin D4

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    DDRD |= (1 << PD4);

6

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    // non-inverted output, toggle OC1B on compare match

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    TCCR1A |= (1 << COM1B0) | (1 << WGM10) | (1 << WGM11);

9

10

    // select OCR1B is TOP for WGM10:3 == 1; detemine counting sequence

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    TCCR1B = (1 << WGM12) | (1 << WGM13);

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13

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    OCR1B = 0; // toggle on TCNT1 == 0

15

    OCR1A = 7811; // set TOP value for PWM1A, toggle on TCNT1 = 7811

16

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    // select prescaler 1024, start timer

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    TCCR1B |= (1 << CS12) | (1 << CS10);

19

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    ...

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    for(;;) { ... }

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    return 0;

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}

This should imo produce a pulsed output with a frequency 1Hz on port 
OC1B. Thus, if I connected a LED to Pin D4, it should toggle every 1 
second.
BUT, sadly, that does not happen. I'd very much appreciate any advice on 
how to make it work.
[c]
int main(void) {
    // CTC mode Timer0
    TCCR0 |= (1 << WGM01);
    // select prescaler 1024
    TCCR0 |= (1 << CS00) | (1 << CS02);
    // interrupt @625Hz
    OCR0 = 25 - 1;
    // use internal CPU interrupt vector
    TIMSK |= (1 << OCIE0);

    // activate OC1B as outputs (PIN D4)
    DDRD |= (1 << PD4);

    // non inverted output, toggle on compare match
    TCCR1A |= (1 << COM1B0) | (1 << WGM10) | (1 << WGM11);
    // select OCR1B is TOP for WGM10:3 == 1; detemine couting sequence

    TCCR1B = (1 << WGM12) | (1 << WGM13);

    // set TOP value for PWM1A
    OCR1B = 0;
    OCR1A = 15383;//PWM_MAX-1;

    // select prescaler 1024
    TCCR1B |= (1 << CS12) | (1 << CS10);

    // select external interrupts INT0, INT1, INT2
    MCUCR = (1 << ISC01) | (1 << ISC11);

    // enable fetching interrupts
    GICR |= (1 << INT0) | (1 << INT1) | (1 << INT2);

    // enable interrupt service routines
    sei();

    DDRC |= 0xff;

    for (;;) {
        PORTC++;
        _delay_ms(50);
    }

    return 0;
}
[\c]