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

#define Relay_On DDB3
#define Relay_Off DDB4
#define Output_Pin DDB1
#define Input_Pin DDB2

#define bit_flip(p,m) ((p) ^= (m))

const unsigned long Alarm = 600; //Time in seconds that must pass without signal from Pi before power is reset
unsigned long Timer_time; //Tracks time since last signal from Pi

ISR(INT0_vect) //Interrupt routine which is called when signal is recieved from Pi
{
	Timer_time = 0; //Reset timer
}

void Turn_relay_off(void) //turns relay off
{
	bit_flip(PORTB,(1<<Relay_Off));
	_delay_ms(1000);
	bit_flip(PORTB,(1<<Relay_Off));
}


void Turn_relay_on(void)  //turns relay back on
{
	bit_flip(PORTB,(1<<Relay_On));
	_delay_ms(1000);
	bit_flip(PORTB,(1<<Relay_On));
}


void reset_pi(void)  //function called to reset Pi
{
	
	
	 bit_flip(PORTB,(1<<Output_Pin));  //Sends signal to turn Pi off (just in case something goes wrong and Pi is still on
	 _delay_ms(1000);					//we dont want to cut power and risk damaging SD card)
	 bit_flip(PORTB,(1<<Output_Pin));
	 _delay_ms(15000);
	 

	
	Turn_relay_off();
	
	_delay_ms(5000);
		
	Turn_relay_on();

	_delay_ms(30000);       //wait for Pi to turn back on


}

ISR(TIMER0_COMPA_vect)
{
	//Timer interrupt called ever 0.25 seconds
    Timer_time++;
    if (Timer_time == Alarm*4) //Alarm*4 since called every 0.25 seconds
    {
        reset_pi(); //Resets pi if Alarm time is reached
		Timer_time = 0;	
    }
}

int main(void)
{
	_delay_ms(3000);
	
	//Set pins to correct state
	DDRB = (1<<Relay_On) | (1<<Relay_Off) | (1<<Output_Pin) | (0<<Input_Pin);
    PORTB =  (0<<Relay_On) | (0<<Relay_Off) | (1<<Output_Pin) | (1<<Input_Pin);
	
	bit_flip(PORTB,(1<<Relay_On)); //Makes sure that the power to pi is initially on
	_delay_ms(1000);
	bit_flip(PORTB,(1<<Relay_On));
   
    cli(); // Disable global interrupts


	//Initialize interrupt on DDB2 
	MCUCR = 1<<ISC01;
    GIMSK = 1<<INT0; 	
	
	//Initialize timer interrupt to be called every 0.25 seconds
	TCCR0A = 0;     
    TCCR0B = 0;    
    OCR0A = 243;
    TCCR0A |= (1 << WGM01);
    TCCR0B |= ((1 << CS02) | (1 << CS00));
    TIMSK |= (1 << OCIE0A);
	
	
	Timer_time = 0;

	
	sei();
	
	while(42)
	{
		
	}
}