// Jeffery Durand

// First Code for AVR! Starting from scratch to learn the details
// Next version build off of this one

// Good practice: specify the pin numbers and the components attached to them:

// 
// v_01: if button pressed, led blinks every 10th of second
//

// 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 */

int main (void)
{
  /* Initialization */
  DDRA = 0b10000000; // configure PA7 as output, rest of pins as input
  DDRA |= (1 << PA7); // equivalent : |= is like += but with | the OR op, << is bit shifting the left by the right (int)

  PORTA = 0b00001000; // set pull-up resistor at PA3
  PORTA &= (1 << PA3); // testing the notation (nice because of manipulation possibilities)

  /* Event Loop */
  while (1)
  {
    /* action */
    if ((PINA & 0b00001000) == 0) // meaning the input on PA3 is low, so ground is connected, so button is pressed
    {
      PORTA |= (1 << PA7); // turn the LED pin on
      _delay_ms(10); // wait
      PORTA = ~((1 << PA7) | ~PORTA); // turn the led pin off
      _delay_ms(10);
    }
    else 
    {
      PORTA = ~((1 << PA7) | ~PORTA); // turn the led pin off
    }
  }

  return (0); // never reached 
}