source: avrstuff/test_2313_muserial/main.c@ f51aacc

#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/wdt.h>
#include <avr/pgmspace.h>
#include <util/delay.h>

#include <string.h>
#include <stdbool.h>

// muSerial: ATTiny2313 - LED = PD6
// K4KUSB: ATTiny2313 - LED = PB2
#define DDRLED DDRB
#define PORTLED PORTB
#define LEDBIT 1 << PB2

int main() {
        wdt_enable(WDTO_2S);
    // configure timer 0 for a rate of 16M/(256 * 256) = ~244Hz
    TCCR0A = 0;          // timer 0 prescaler: 256
        TCCR0B = 4;

        //debug LED - output
        DDRLED |= 255;

        PORTLED = 0;

        // Serial PORT
        UBRRH = 0;
        UBRRL = 10;

        UCSRB = (1<<RXEN) |(1<<TXEN);
        UCSRC = (1 << UCSZ1) | (1 << UCSZ0);

        while(1) {
                wdt_reset();


                // check timer if we need periodic reports
                if (TIFR & (1 << TOV0)) {
                        TIFR = (1 << TOV0); // reset flag
                        PORTLED ^= LEDBIT;

                        UDR = 'H';
                }
        }

        return 0;
}