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#include <avr/io.h>

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#include <util/delay.h>

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#define false       0

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#define true        1

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#define SBI(port, bit) do { port |= (1 << (bit)); } while (0)

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#define CBI(port, bit) do { port &= ~(1 << (bit)); } while (0)

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int main (void)

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{

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    // LED

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    SBI(DDRB, DDB5);

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    while (true) {

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        // flip

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        PORTB ^= (1 << PORTB5);

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        // busyloop

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        _delay_ms(1000);

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    }

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}