/*
* SmartLED.c
*
* Created: May 2016
* Author: Mar.lux
*
*
* Device: Atmel ATTiny25/45/85(V)
*
* Power consumption (3V):
*
* Standby: 0.1 uA
* Active (no LED): 670 uA
* Active (with LED, bright light): approx. 5.7 mA
* Active (with LED, darkness): approx. 700 uA
*
*/
#include <avr/io.h>
#include <avr/power.h>
#include <avr/sleep.h>
#include <avr/interrupt.h>


#define LED PB4
#define SNS PB3
#define MUXCONFIG ((1 << MUX1) | (1 << MUX0)) // PB3

#define ENON PB0
#define ENBLINK PB1
#define ENFLASH PB2


#define BASELINE 9 // discharge in complete darkness


volatile uint8_t Discharge = 0;
volatile uint16_t DischargeSum = 0;
volatile uint8_t level = 8;
volatile uint8_t factor = 0;

volatile uint8_t TimerCounter = 0;
volatile uint8_t LightDuty = 0xff; // Fraction of time the LED is on (0xff: always, 0x80 blinking, 0x0f flashing)

void initDevice();

int main(void)
{		
	/* Replace with your application code */
	initDevice();
	//PORTB |= (1<<LED);  // Turn on LED
	while (1)
	{
		
		while ((~PINB & ((1 << ENON) | (1 << ENBLINK) | (1 << ENFLASH)) )) // As long as Pin is low
		{
			// keep device active
			if (~PINB & (1<<ENON)) LightDuty = 0xff;
			if (~PINB & (1<<ENBLINK)) LightDuty = 0x80;
			if (~PINB & (1<<ENFLASH)) LightDuty = 0x0f;					
		}
		ADCSRA &= ~(1 << ADEN); // turn off ADC to save power in sleep
     	GIMSK |= (1 << PCIE); /* enable pin-change interrupts */	
		sleep_mode();
		GIMSK &= ~(1 << PCIE); /* disable pin-change interrupts */
		ADCSRA |= (1 << ADEN);
		DischargeSum = 0; //start with low light level after power-down
	}
}

void initDevice()
{
	//// slow down, save power
	clock_prescale_set(clock_div_8);  // 1 MHz
	PRR |= (1<<PRTIM1) | (1<<PRUSI); // save power, page 38
	ACSR |= (1<<ACD); //Disable the analog comparator

	//// Configur I/O
	DDRB |= (1<<LED) | (1<<SNS);  // define LED and SNS as outputs
	PORTB |= ~((1<<LED) | (1<<SNS)); // Pull up resistor on unconnected pins

	//// prepare compare match
	OCR0A = 136; // Turn on LED
	OCR0B = 140; // Turn off LED, charge for measurement.
	
	TIFR = (1 << TOV0); // clear interrupt. do not use a read-modify-write cycle
	TCNT0=0; // Reset counter
	TCCR0B |= (1<<CS01); //set prescaler to 8, p.80
	
	TIMSK |= (1<<OCIE0A) | (1<<OCIE0B) | (1<<TOIE0); // compare match interrupts, overflow interrupt enable

	// Configure ADC
	ADMUX |= (1 << ADLAR) | MUXCONFIG; // VCC as voltage reference, left adjust result, set MUX        p134
	ADCSRA |= (1 << ADPS0) | (1 << ADEN); // Prescaler 2, enable ADC

	PCMSK |= (1 << ENON) | (1 << ENBLINK) | (1 << ENFLASH); /* enable specific interrupt for enable pin */
	set_sleep_mode(SLEEP_MODE_PWR_DOWN);
	sei();
}

ISR(TIMER0_OVF_vect) // overflow interrupt
{
	ADCSRA |= (1<<ADSC); // start ADC

	// Discharge level is proportional to amount of light
	// Set LED light level
	OCR0A = 140-level; // min: 12, max 136
}


ISR(TIMER0_COMPA_vect) // Compare match interrupt A
{
	// Set LED light factor
	DDRB |=  (1<<SNS); //sns as output
	if ((TimerCounter < LightDuty) && ((TimerCounter & 0b0000111) < factor))
	PORTB |= (1<<LED); // turn on LED
}

ISR(TIMER0_COMPB_vect) // Compare match interrupt B
{
	// Turn off and reverse charge LED
	PORTB &= ~(1<<LED);  // LED to Ground
	PORTB |= (1<<SNS); // SNS high

	DDRB &= ~(1<<SNS); //SNS as input
	PORTB &= ~(1<<SNS); // turn off pullup
	
	TimerCounter++;
	Discharge = (DischargeSum + 8) >> 4; // smooth out noise in the ADC conversion
	//Discharge = (DischargeSum + 128) >> 8;
	DischargeSum = DischargeSum - Discharge + (255-ADCH);

	if (Discharge > BASELINE)
	Discharge -= BASELINE;
	else
	Discharge = 0;

	uint8_t shift = 0;
	if (Discharge > 31)  shift = 1;
	if (Discharge > 63)  shift = 2;
	if (Discharge > 127) shift = 3;
	
	factor = 1 << shift;
	level = ((Discharge >> shift)+1) << 2;
}

EMPTY_INTERRUPT(PCINT0_vect); // Pin change interrupt: Do nothing, just wake up