//
//
// helloworld.c
// Hello World // Morse code
// .... . .-.. .-.. --- / .-- --- .-. .-.. -..
//
// Says "HELLO WORLD" in morse code by blinking an LED at
// the touch of a button.
//
//
// Alex Berke
// Based on code supplied by Neil Gershenfeld
// http://academy.cba.mit.edu/classes/embedded_programming/hello.ftdi.44.echo.c
//
// (c) Massachusetts Institute of Technology 2010
// This work may be reproduced, modified, distributed,
// performed, and displayed for any purpose. Copyright is
// retained and must be preserved. The work is provided
// as is; no warranty is provided, and users accept all 
// liability.
//

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

#define output(directions, pin) (directions |= pin) // set port direction for output
#define input(directions,pin) (directions &= (~pin)) // set port direction for input
#define set(port, pin) (port |= pin) // set port pin
#define clear(port, pin) (port &= (~pin)) // clear port pin
#define pin_test(pins, pin) (pins & pin) // test for port pin
#define bit_test(byte, bit) (byte & (1 << bit)) // test for bit set
#define led_delay() _delay_ms(100)

// Set up morse code constants:
// The length of a "dot" is 1 unit.
// The length of a "dash" is 3 units.
// The space between parts of 1 letter is 1 unit.
// The space between letters is 3 units.
// The space between words is 7 units.
#define DOT_MS 100 // a dot is the length of one unit in morse code
#define dot_delay() _delay_ms(DOT_MS)
#define dash_delay() _delay_ms(3*DOT_MS)


// Define the pins to be used as the input (button) and output (LED).
#define LED_PORT PORTA
#define LED_DIRECTION DDRA
#define LED_PIN (1 << PA7)
#define BUTTON_PINS PINB
#define BUTTON_PORT PORTB
#define BUTTON_DIRECTION DDRB
#define BUTTON_PIN (1 << PB2)


int main (void) {
    //
    // main
    //
    // set clock divider to /1 (Make it faster)
    //
    CLKPR = (1 << CLKPCE);
    CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);

    // Initialize LED pin (output).
    clear(LED_PORT, LED_PIN);
    output(LED_DIRECTION, LED_PIN);
    // Initialize the button pin (input).
    set(BUTTON_PORT, BUTTON_PIN); // Turn on pull-up -- I don't understand this.
    input(BUTTON_DIRECTION, BUTTON_PIN);

    // main loop
    while (1) {
        if (pin_test(BUTTON_PINS, BUTTON_PIN))
            clear(LED_PORT, LED_PIN);
        else
            say_hello_world();
    }
}


void say_hello_world() {
    /* Says "Hello World" in morse code, i.e.:
     * .... . .-.. .-.. --- / .-- --- .-. .-.. -..
     * 
     * A dot is expressed as a short blink of the LED.
     * A dash is expressed as a long blink of the LED.
     */
    // H
    dot();
    dot();
    dot();
    dot();
    letter_space();
    // E
    dot();
    letter_space();
    // L
    dot();
    dash();
    dot();
    dot();
    letter_space();
    // L
    dot();
    dash();
    dot();
    dot();
    letter_space();
    // O
    dash();
    dash();
    dash();
    letter_space();
    
    word_space();
    
    // W
    dot();
    dash();
    dash();
    letter_space();
    // O
    dash();
    dash();
    dash();
    letter_space();
    // R
    dot();
    dash();
    dot();
    letter_space();
    // L
    dot();
    dash();
    dot();
    dot();
    letter_space();
    // D
    dash();
    dot();
    dot();
    letter_space();
  }
  
  void dot() {
      /*
      * Express a dot in morse code.
      */
      set(LED_PORT, LED_PIN);
      dot_delay();
      clear(LED_PORT, LED_PIN);
      dot_delay();
  }
  
  void dash() {
    /*
     * Express a dash in morse code.
     */
      set(LED_PORT, LED_PIN);
      dash_delay();
      clear(LED_PORT, LED_PIN);
      dot_delay();
  }
  
  void letter_space() {
    /*
     * Express the space between letters in morse code.
     * 2 extra units of no signal.
     * Assumes that it follows a LOW write to the LED for 1 unit of time.
     */
    _delay_ms(2*DOT_MS);
  }
  
  void word_space() {
    /*
     * Express the space between letters in morse code.
     * 6 extra units of no signal.
     * Assumes that it follows a LOW write to the LED for 1 unit of time.
     */
     _delay_ms(6*DOT_MS);
  }