/*
 * main.c
 *
 * A small program for the ATtiny44a to keep LEDs on for a certain amount of time
 * after hearing a noise.
 *
 * Created for the "Lighten Up Your Room Interior With A Summer Touch" instructable.
 *
 *  Created on: 9 Mar 2012
 *      Author: d3h
 */

#define ON_FOR 300 // time in seconds to keep the lights on after hearing a noise
#define NOISE_THRESHOLD 25 // noise picking threshold
#define NOISE_DURATION 2 // minimum duration of the noise to be picked

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

volatile unsigned char secondsCounter = 0;
volatile unsigned char noiseCounter = 0;

int main (void) {
	unsigned char noiseHeard = 0; // 1 if noise heard, 0 otherwise

	// ADC initialisation
	ADMUX |= (1 << REFS1); // set ADC reference to 1.1V
	ADCSRB |= (1 << ADLAR); // left adjust ADC result to allow easy 8 bit reading
	// no MUX values needed to be changed to use ADC0 (PA0) for ADC input
	// set conversion timing to Fcpu/16, auto-triggering on, enable ADC interrupt
	// enable ADC, start A2D conversions
	ADCSRA |= (1 << ADPS2) | (1 << ADATE) | (1 << ADIE) | (1 << ADEN) | (1 << ADSC);

	// timer initialisation
	TCCR1B |= (1 << WGM12); // configure timer 1 for CTC mode
	TIMSK1 |= (1 << OCIE1A); // enable CTC interrupt
	OCR1A = 15624; // set CTC compare value to 1Hz at 1MHz AVR clock, with a prescaler of 64
	TCCR1B |= (1 << CS10)|(1 << CS11); // set up timer at Fcpu/64

	sei(); //  enable global interrupts

	DDRA |= (1 << DDA2); // set PA2 as output
	PORTA &= (0 << PA2); // set LEDs to be initially OFF

	for (;;) {
		if (noiseHeard && secondsCounter >= ON_FOR) {
			// no noise was heard for ON_FOR seconds, switch LEDs OFF
			PORTA &= (0 << PA2); // set the LEDs OFF
			noiseHeard = 0;
		}
		if (noiseCounter >= NOISE_DURATION) {
			// set the LEDs ON (or keep them on) for ON_FOR seconds
			PORTA |= (1 << PA2);
			noiseHeard = 1;
			secondsCounter = 0; // start counting ON_FOR seconds
			noiseCounter = 0; // keep listening for further sounds
		}
	}

	return 1; // should never reach here
}

// Interrupts

ISR(TIM1_COMPA_vect) {
	// fires when the timer ticks
	secondsCounter++;
}

ISR(ADC_vect) {
	// fires when an ADC conversion occurs
	if (ADCH >= NOISE_THRESHOLD) noiseCounter++;
	else noiseCounter = 0;
}