Led + Button + Timer + UART

Материал из Automata.

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

#define BUT_PIN 0x10
#define LED_PIN 0x01
#define TST_MES 0xA5
#define ONE_SEC 31250
#define MSG_LEN 12

const char msg[] = "set Hz freq";
char led_stat;

void snd_byte (uint8_t byte)
{
    UDR = byte;
    while (!(UCSRA & _BV(TXC)));
    UCSRA |= _BV(TXC);
}

void but_test (void)
{ 
    if (!(PINB & BUT_PIN)) { 
        _delay_ms(5); 
        led_stat ^= 1; 
        while (!(PINB & BUT_PIN)); 
        _delay_ms(5); 
   } 
} 

inline void led_trig (void)
{ 
    PORTB ^= LED_PIN;
}

ISR (TIMER1_COMPA_vect)
{
    led_trig();
}

ISR (USART_RX_vect)
{
    OCR1A = ONE_SEC/UDR; 
    snd_byte('O');
    snd_byte('K');
}

int main ()
{
    //pin 0 - led act GND, pin 4 - button act GND
    DDRB = 0x01;
    PORTB = 0x10;
	
    //CTC, presc 256
    TCCR1B = _BV(WGM12) | _BV(CS12);
    TIMSK  = _BV(OCIE1A);
    OCR1A  = ONE_SEC;

    //19.2k , 8 db, 1sb, no parity
    UBRRH = 0;
    UBRRL = 25;	
    UCSRB = _BV(RXCIE) | _BV(RXEN) | _BV(TXEN);
    UCSRC = _BV(URSEL) | _BV(USBS) | _BV(UCSZ0) | _BV(UCSZ1);	

    for (int i = 0; i < MSG_LEN; ++i)
        snd_byte(msg[i]);

    sei();
	
    while (1) {
        but_test();
	 TIMSK = led_stat ? _BV(OCIE1A) : 0;
    } 

    return 0;
}