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

#define queueDataInSize 8

struct queue
{
	char * data;
	volatile unsigned char begin;
	volatile unsigned char end;
	unsigned char size;
};

struct queue dataIn;

unsigned char nextQueueIndex(unsigned char i, unsigned char n)
{
	if(i==n-1)
		i=0;
	else
		i++;

	return i;
}

ISR(USART_RXC_vect)
{
	volatile unsigned char tmp=nextQueueIndex(dataIn.end,dataIn.size);

	unsigned char data=UDR;
	if(tmp!=dataIn.begin)
	{
		dataIn.data[dataIn.end]=data;
		dataIn.end=tmp;
		PORTA=PORTA&0xf8|dataIn.end;
	}
}

int main(void)
{

	dataIn.data=malloc(queueDataInSize);
	dataIn.size=queueDataInSize;
	dataIn.begin=0;
	dataIn.end=0;

	DDRA=0xff;
	UBRRL=51;
	//UCSRA=0;
	UCSRB=0x98;
	UCSRC=0x86;

	SREG|=1<<SREG_I;
	
	PORTA=PORTA&0xf8|dataIn.begin;
	PORTA=PORTA&0x1f|dataIn.end<<5;
	
	while(1)
	{
		if(dataIn.begin!=dataIn.end)
		{
			UDR=dataIn.data[dataIn.begin];
			dataIn.begin=nextQueueIndex(dataIn.begin,dataIn.size);
			PORTA=PORTA&0x1f|dataIn.begin<<5;

			unsigned char i;
			for(i=0; i<100; i++)
				_delay_ms(10);
		}
	};
	return 0;
}