/*
 * decision_box_be.c 
 *
 * Created: 15.03.2015
 *  Author: nqtronix
 * Package: Decision Box BE
 *      ID: 430456905935
 * Version: 1.0
 * Release: 17.03.2015
 * License: BY-NC-SA
 *
 * Content:
 * - decision_box.c	(program)[this]
 * - pinout.h		(maps IO)
 * - user.h			(user defined values)
 *
 * Description:
 * This program is a remake of the "Arduino decision box V2.0 (Attiny85)" by
 * Victor8o5: http://www.instructables.com/id/Arduino-decision-box-V20-Attiny85/
 * The code is pin-compatible to the latest version at release, but not feature
 * identical. For more information check the corresponding instructable "'Arduino'
 * Decision 'Box' BE (Attiny85)":
 * http://www.instructables.com/id/Arduino-Decision-Box-BE-Attiny85/
 *
 * DO NOT MODIFY THE MAPPING WITHIN THE MAIN C FILE. Modify the pinout.h
 * DO NOT MODIFY THE VALUES WITHIN THE MAIN C FILE. Modify the user.h
 */

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

#include "pinout.h"										//load pin mapping
#include "user.h"										//load user defined values

//global variables
uint8_t button_press = 0;								//button pressed if low
uint8_t preSleep_MCUCR = 0;								//contains contents of MCUCR prior sleep

uint8_t debounce = 0;									//= 1 if button recently pressed/released
uint8_t isr_PCINT0 = 0;									//= 1 if interrupt executed 
uint8_t isr_WDT= 0;										//= 1 if interrupt executed 

//forward decelerations
uint8_t randomByte();

int main(void)
{	
	//Initialize LEDs
	DDR_LED |= ((1<<DDR_LEDR)|(1<<DDR_LEDG)|(1<<DDR_LEDY));
	
	//disable WTD (as recommended in datasheet)
	WDTCR	= ((1<<WDCE)|(1<<WDE));
	WDTCR	= 0;
	
	//un-power unused modules
	PRR		|= ((1<<PRTIM1)|(1<<PRTIM0)|(1<<PRUSI));	//timer1, timer0, USI
	ACSR	|= (1<<ACD);								//analog comparator
  //DDRB	&= DDRB_UNUSED;								//0 after boot by default
	PORTB	|= PORTB_UNUSED;							//enable pull-up, defined level reduces current consumption
	
	//Initialize button (IO0)
	PORT_IO	|= (1<<PORT_IO0);							//enable int. pull-up
	
	//Check for external pull-down
	ADMUX	= ((1<<ADLAR)|ADMUX_IO0);					//select channel & left adj.
	ADCSRA	= ((1<<ADEN)|((3-CLKPR)<0? 0:(3-CLKPR)));	//enable & set prescaler in relation to system prescaler (max speed)
	ADCSRA	|= (1<<ADSC);								//start conversation	
	while (ADCSRA&(1<<ADSC));							//wait till result
	if(ADCH < PERCENTAGE_THRESHOLD)						//compare to defined value
	{
		//external pull-down found
		PORT_IO &= ~(1<<PORT_IO0);						//disable pull-up
		button_press = 1;								//set button pressed if high
	}
	ADCSRA	= 0;										//Turn off ADC to save power
	PRR		|= (1<<PRADC);								//un-power ADC
	
	//Initialize sleep mode
	PCMSK	|= (1<<PCINT_IO0);							//enable pin change interrupt @ button
	GIMSK	|= (1<<PCIE);								//enable pin change interrupt
	sei();												//enable global interrupts
	
	preSleep_MCUCR = MCUCR;								//store original contents
	set_sleep_mode(SLEEP_MODE_PWR_DOWN);				//select power-down
	sleep_mode();										//enter sleep
	
    while(1)											//interrupt management loop
	{
		MCUCR	= preSleep_MCUCR;							//restore contents
		//Button Press
		if(isr_PCINT0)
		{
			isr_PCINT0 = 0;
			
			//initialize watchdog timer
			if(debounce)									//if executed multiple times within WDT period
				wdt_reset();								//resets watchdog timer/ extend WTD period
			else
			{
				//debounce mode
				WDTCR	= (1<<WDCE);
				WDTCR	= ((1<<WDIE)/*|(1<<WDP0)*/);		//enable interrupts @16ms
				debounce = 1;
			}

			//initialize sleep mode
			preSleep_MCUCR = MCUCR;							//store original contents
			set_sleep_mode(SLEEP_MODE_IDLE);				//select idle (many interrupts expected)
			
			isr_WDT = 0;
		}
		
		//Watchdog event
		else if(isr_WDT)
		{
			isr_WDT = 0;
			
			//Debounce mode
			if (debounce)										//debounce routine is finished
			{
				//quit debounce routine / button state stable
				debounce = 0;
				
				if (!(PIN_IO & (1<<PIN_IO0)) ^ button_press)	//button pressed as defined
				{
					WDTCR	= (1<<WDCE);						//disable watchdog timer
					WDTCR	= 0;
					
					//Turn all LEDs off
					PORT_LED &= ~((1<<PORT_LEDR)|(1<<PORT_LEDG)|(1<<PORT_LEDY));
					
					//generate output
					uint8_t random = randomByte();				//get random data
					
					if(random > 255-PERCENTAGE_RED)				//chance for "YES" / RED
					PORT_LED |= (1<<PORT_LEDR);
					else if(random < PERCENTAGE_GREEN)			//chance for "NO" / GREEN
					PORT_LED |= (1<<PORT_LEDG);
					else										//chance for "MAYBE" / YELLOW
					PORT_LED |= (1<<PORT_LEDY);
				}
				else											//button released as defined
				{
					//LED timeout mode
					WDTCR	= (1<<WDCE);
					WDTCR	= ((1<<WDIE)|(1<<WDP2)|(1<<WDP1)|(1<<WDP0));//enable interrupts @ 2s
				}
			}
			//LED timeout mode
			else
			{
				//Turn all LEDs off
				PORT_LED &= ~((1<<PORT_LEDR)|(1<<PORT_LEDG)|(1<<PORT_LEDY));
				WDTCR	= (1<<WDCE);							//disable watchdog timer
				WDTCR	= 0;
			}
			
			//initialize sleep mode
			preSleep_MCUCR = MCUCR;								//store original contents
			set_sleep_mode(SLEEP_MODE_PWR_DOWN);				//select power down (very few interrupts expected)
		}
		if(!((isr_PCINT0)||(isr_WDT)))							//if no interrupt was executed while last loop
			sleep_mode();
	}
}

uint8_t randomByte()
{	
	static uint16_t seed = 0;
	uint16_t result;
	
	//backup value of random channel
	uint8_t backup_DDR = DDR_RAN;
	uint8_t backup_PORT = PORT_RAN;
	
	//Prepare random channel
	DDR_RAN	&= ~(1<<DDR_RAN0);							//input
	PORT_RAN&= ~(1<<PORT_RAN0);							//no pull-up
	
	//Initialize random module
	PRR		&= ~(1<<PRADC);								//power ADC
	ADMUX	= ADMUX_RAN0;								//select LED as input for noise
	ADCSRA	= ((1<<ADEN)|((3-CLKPR)<0? 0:(3-CLKPR)));	//enable & set prescaler in relation to system prescaler (max speed)
	
	//generate seed
	if(seed == 0)
	{
		for(uint8_t i=8; i; i--)						//counting down is slightly faster codewise
		{
			ADCSRA	|= (1<<ADSC);						//start conversation
			while (ADCSRA&(1<<ADSC));					//wait till result
			seed = (seed<<1)+(ADCL&1);					//shift LSB of ADC into LSB of byte
			ADCH;										//allow next conversation
		}
	}
	
	//exit random module
	ADCSRA	= 0;										//Turn off ADC to save power
	PRR		|= (1<<PRADC);								//un-power ADC
	
	//load backup value
	DDR_RAN = backup_DDR;
	PORT_RAN = backup_PORT;
	
	//Pseudo randomness, code based on ZABEX' "looping louie" (http://www.zabex.de/frames/loopinglouie.html)
	result = 181*seed+359;
	seed = result;
	
	return (result>>8);
}

ISR(PCINT0_vect)
{
	isr_PCINT0 = 1;
}

ISR(WDT_vect)
{
	isr_WDT = 1;
}