// Jeffery Durand

// 
// v_04: The brightness will decrease at every press
// 

// Button   PA3 (pin 10)
// LED      PA7 (pin 6)
// Cristal  Xtal 1 & 2 (pin 2 & 3)
#include <avr/io.h> // basic library
#include <util/delay.h> /* Functions to waste time */
#include <stdbool.h> // contains the booleans
//#include <stdlib.h> // contains rand()
#include <math.h> // contains math functions, but is big!

// bitwise manipulations ! (though for several at a time the explicit manipulation is nice)
// WARNING: no spacing between the name and params: BIT (x) will crash
#define BIT(x) (1 << x)
#define bit_get(p,x) (p & BIT(x)) // to read: makes all zero except wanted bit x
#define bit_set(p,x) (p |= BIT(x)) // assign a 1 to wanted bit x
#define bit_clear(p,x) (p &= ~BIT(x)) // assign a 0 to wanted bit x

void flash (void)
{
  bit_set (PORTA, PA7); // turn the LED pin on
  _delay_ms(100); // wait
}

int main (void)
{
  /* Initialization */
  bit_set (DDRA, PA7);
  bit_set (PORTA, PA3);
  // full brightness at first
  int delay = 0;
  uint8_t count = 0; // unsigned 8-bit integer
  // need to declare i here, does not work in for loop
  int i;
  // tells if the button has just been pressed
  bool pressed = false;

  /* Event Loop */
  while (1)
  {
    /* action */
    if (bit_get(PINA, PA3) == 0 && pressed == false) // meaning the input on PA3 is low, so ground is connected, so button is pressed
    {
      bit_clear (PORTA, PA7); // turn the led pin off
      // increase count and use exponential growth for the delay
      count = (count + 1) % 12;
      delay = pow (2, count);
      // set to pressed true so that the delay is not changed again while button remains pressed
      pressed = true;
    }
    else 
    {
      if (bit_get(PINA, PA3) != 0)
      {
        pressed = false;
      } 
      bit_clear (PORTA, PA7); // turn the led pin off
      // need the for loop, cannot use variables inside _delay
      for (i = 0; i < delay; i++)
      {
        _delay_us(1);
      }
      bit_set (PORTA, PA7); // turn the LED pin on
      _delay_us(1); // wait
    }
  }
  return (0); // never reached 
}