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

#define F_CPU 20000000



void USART_Init( unsigned int baud )
{
	/* Set baud rate */
	UBRR0H = (unsigned char)(baud>>8);
	UBRR0L = (unsigned char)baud;
	/* Enable receiver and transmitter */
	UCSR0B = (1<<RXEN0)|(1<<TXEN0);
	/* Set frame format: 8data, 2stop bit */
	UCSR0C = (1<<USBS0)|(3<<UCSZ00);
}


void USART_Transmit( unsigned char data )
{
	/* Wait for empty transmit buffer */
	while ( !( UCSR0A & (1<<UDRE0)) );
	/* Put data into buffer, sends the data */
	UDR0 = data;
}


unsigned char USART_Receive( void )
{
	/* Wait for data to be received */
	while ( !(UCSR0A & (1<<RXC0)) )
	{
		PORTD = 0x10;
		_delay_ms(500);
		PORTD = 0x00;
		_delay_ms(500);	
	}
	/* Get and return received data from buffer */
	return UDR0;
}

void USART_Flush( void )
{
	unsigned char dummy;
	while ( UCSR0A & (1<<RXC0) ) dummy = UDR0;
}

void main (void)
{

	USART_Init(9600);
	DDRD = 0xFF;
	PORTD = 0x10;

	while(1) 
	{
		if ('a' == USART_Receive())
		{
			PORTD = 0x10;
			_delay_ms(500);
			PORTD = 0x00;
			_delay_ms(500);	
			PORTD = 0x10;
			_delay_ms(500);
			PORTD = 0x00;
			_delay_ms(500);		
		}
	}
}