#include <avr/io.h>
#include <avr/iom8.h>
#include <avr/interrupt.h>

//variables
#define portio      PIND
#define portiow     PORTD
#define rxled       PD7
#define rele        PD6

#define ubrr 51
#define MAX_BUFFSIZE 3

volatile short int ovf0cnt;
volatile short int btnsw_right = 0;

volatile unsigned char usart[MAX_BUFFSIZE];
volatile unsigned char usart1 = 0;

unsigned char rx_count = 0;
volatile unsigned char message = 0;

int main(void)
{
  cli();
  ovf0cnt = 0;
  UCSRB = (1<<RXEN)|(1<<TXEN)|(1<<RXCIE)|(1<<TXCIE)|(0<<UDRIE)|(0<<UCSZ2);
  UCSRC = (1<<URSEL)|(0<<UMSEL)|(0<<UPM1)|(0<<UPM0)|(0<<USBS)|(1<<UCSZ1)|(1<<UCSZ0)|(0<<UCPOL);
  UBRRH = (unsigned char) (ubrr>>8);
  UBRRL = (unsigned char) ubrr;
  
  TCCR0 = (1<<CS02 | 0<<CS01 | 0<<CS00);  
  DDRD = (1 << PD7 | 1 << PD6 | 0<<PD5 | 1<<PD4 | 0<<PD2);
  PORTD |= (1 << PD5 | 1<<PD4);
  sei();

  while(1)
  {
    ;  
  }
}

ISR(TIMER0_OVF_vect)
{
  if(ovf0cnt) {
    portiow ^= (1 << rxled);
    if(--ovf0cnt == 0)
      portiow ^= (1 << rele);
  }
}

ISR(USART_RXC_vect)
{
  if((rx_count < MAX_BUFFSIZE) && !message)
    usart[rx_count++] = UDR;

  if((rx_count == MAX_BUFFSIZE) && !message)
  {
    UDR = usart[1];
    
    message = 1;
    switch(usart[0])
    {
      case '1': usart1 = usart[1]; ovf0cnt = usart[2]; message = 1;
        switch(usart1) {
	  case '1': portiow |= (1 << rele); break;
	  case '2': portiow &= ~(1 << rele); break;
	  case '3': ovf0cnt = 400; break;
	  default: UDR = 'C';  
	} break;
      default : UDR = 'X';
    }
    message = 0;
  }
}