/* DIY Annoy-a-tron source code
 * (c) 2007 Jurre "Kipmans" Hanema, <kipmans@gmail.com>
 * Idea (c) ThinkGeek
 *
 * Released under "THE BEER-WARE LICENSE" (Revision 42):
 * <kipmans@gmail.com> wrote this file. As long as you retain this notice you can 
 * do whatever you want with this stuff. If we meet some day, and you think this 
 * stuff is worth it, you can buy me a beer in return.
 */
 
#define	F_CPU	4000000		/* 4 MHz crystal */


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


#define	SIX_MINUTES	360000		/* ms */
#define	TWO_MINUTES	120000		/* ms */

#define	STATE_WAITING	1
#define STATE_BEEP2K	2
#define	STATE_BEEP10K	3

#define	MODE_2K		1
#define	MODE_10K	2
#define	MODE_ALT	3

#define	set_output_high(port, bit)	(port |= _BV(bit))
#define	set_output_low(port, bit)	(port &= ~_BV(bit))
 
 
volatile unsigned long int	n_millisecs;
volatile unsigned long int	ms_busy;

volatile unsigned char		isr_calls;
volatile unsigned char		n_halfperiods;
volatile unsigned char		state;
volatile unsigned char		mode;
volatile unsigned char		high;
volatile unsigned char		tmp;

 
ISR(TIMER0_OVF0_vect)
{
	// Called every 0,05 ms
	
	isr_calls++;
	
	if(state == STATE_WAITING && isr_calls >= 20)
	{
		ms_busy++;
		
		if(ms_busy >= n_millisecs)
		{
			if(mode == MODE_2K)
				state = STATE_BEEP2K;
			else if(mode == MODE_10K)
				state = STATE_BEEP10K;
			else
			{
				tmp = rand() / (RAND_MAX / 10 + 1);
				
				if(tmp >= 5)
					state = STATE_BEEP2K;
				else
					state = STATE_BEEP10K;
			}
			
			ms_busy = 0;
		}
		
		isr_calls = 0;
	}
	
	if((state == STATE_BEEP2K && isr_calls >= 5) || (state == STATE_BEEP10K && isr_calls >= 1))
	{
		if(high)
		{
			set_output_low(PORTD, PD2);
			set_output_high(PORTD, PD3);
			high = 0;
		} else
		{
			set_output_high(PORTD, PD2);
			set_output_low(PORTD, PD3);
			high = 1;
		}
		
		n_halfperiods++;
		
		if((state == STATE_BEEP2K && n_halfperiods >= 4) || (state == STATE_BEEP10K && n_halfperiods >= 20))
		{
			ms_busy++;
			
			if(ms_busy >= 1000)
			{
				state = STATE_WAITING;
				set_output_low(PORTD, PD2);
				set_output_low(PORTD, PD3);
				ms_busy = 0;
				n_millisecs = random() / (RANDOM_MAX / SIX_MINUTES + 1) + TWO_MINUTES;
			}
			
			n_halfperiods = 0;
		}
		
		isr_calls = 0;
	}
	
	TCNT0 = 230;
}
 
 
int main()
{
	unsigned char	garbage;
	
	cli();
	
	isr_calls	= 0;
	state		= STATE_WAITING;
	mode		= MODE_2K;
	
	DDRD = _BV(PD2) | _BV(PD3);
	PORTD |= _BV(PD0) | _BV(PD1) | _BV(PD4) | _BV(PD5) | _BV(PD6);
	PORTB |= _BV(PB0) | _BV(PB1) | _BV(PB2) | _BV(PB3) | _BV(PB4) | _BV(PB5) | _BV(PB6) | _BV(PB7);
	
	set_output_low(PORTD, PD2);
	
	TIMSK = _BV(TOIE0);
	TCCR0 = _BV(CS01);
	TCNT0 = 230;
	
	srandom(garbage);
	
	n_millisecs = random() / (RANDOM_MAX / SIX_MINUTES + 1) + TWO_MINUTES;
	
	sei();
	
	while(1)
	{
		if(bit_is_clear(PIND, PD0))
			mode = MODE_2K;
		else if(bit_is_clear(PIND, PD1))
			mode = MODE_10K;
		else
			mode = MODE_ALT;
	}
	
	return 0;
}