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

volatile unsigned long count1 = 15625; // 1 Hz in a clock cycle

// Edge detection flags for the switches
volatile int edge0 = 0; // Switch 1
volatile int edge1 = 0; // Switch 2

void setup() {
  cli(); // Clear global interrupt

  DDRD |= B01000000; // Set Pin 6 as output
  DDRD &= B01111111; // Set Pin 7 as input
  DDRB &= B111110; // Set Pin 8 as input

  // Enabling both the PCINT0 (Port B) and PCINT2 (Port D) to activate
  PCICR |= B00000101;

  // Setting up the switch interrupts
  PCMSK0 |= (1 << PCINT0); // Mask for Pin 8
  PCMSK2 |= (1 << PCINT23); // Mask for Pin 7

  // Setting up Timer1
  TCCR1A = B00000000; // Initialize to 0
  TCCR1B = B00000101; // Pre-scaling to 1024 (max value)

  // Turn on the OVF timer for Ports B and D (1 Hz)
  TIMSK1 = B00000101; 

  // Set the initial clock reading
  TCNT1 = 0xFFFF - count1; // 0xC2F6 or (65535-15625 = 49910)

  sei(); // Setting up all global interrupts

  // Set the appropriate sleep mode for lowest power possible
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);

}

// Interrupt for Timer1 in OVF mode
ISR(TIMER1_OVF_vect) {
  PORTD ^= B01000000; // Toggle LED on Pin 6
  TCNT1 = 0xFFFF - count1; // Reset the timer to most updated clock cycle value
}

// Interrupt Service Request by pressing the switch connected to Pin 8
ISR(PCINT0_vect) {
  edge0 = edge0 + 1; // Increments upon pushing Switch 1

  if (edge0 == 1) {
    // Add the code to decrease the output frequency 
    count1 = count1 * 2;

    // If the following clock cycle number (for 0.5 Hz) is exceeded...
    if (count1 > 31250) {
      count1 = 31250; //... reset clock cycle to highest possible
    } 
  }

  if (edge0 > 1) {
    edge0 = 0;
  }
}

// Interrupt Service Request by pressing the switch connected to Pin 7
ISR(PCINT2_vect) {
  edge1 = edge1 + 1; // Increments upon pushing Switch 2

  if (edge1 == 1) {
    // Add the code to increase the output frequency
    count1 = count1 / 2;

    // If the following clock cycle number (for 8 Hz) is lowered...
    if (count1 < 1953) {
      count1 = 1953; //... reset clock cycle to lowest possible
    }
  }

  if (edge1 > 1) {
    edge1 = 0;
  }
}

void loop() {
  // Serial.println(value); // Used for debugging
  sleep_mode();
}