Dash Dash Dash Dot Dot Dot Dash Dash Dash....

So I was reading through a new arduino book (Beginning Arduino by  Michael McRoberts) that I found online through my school library and the second project they talk about is an SOS morse code blinking LED. Pretty simple. I'm not a huge fan of simple, I like interesting times. So I decided to skip what the book wanted me to do and make my own general morse code blinker.

First, the circuit. Its pretty simple, just an LED connected to pin 2 of the arduino, it has a 220 ohm resister to protect the led.

The fun part was the code. I wanted it to be able to display any message typed into the computer. So first I defined what a dash and a dot are. Thank you Wikipedia :) Then its some quick and dirty letter conversions and a loop to read in data from the serial port and we are off


Code:

/**
 * Author: John Stemberger
 * Date: December 18, 2011
 * Description: A morse code blinker. This will blink a sentence in Morse code. The sentence will either be the defualt sentence (SOS) or a sentence read in from the serial connection if one exists
 **/

char sentence[255] = "SOS\0";
int ledPin = 2;
int counter = 0;
int dotLength = 100;

void setup()
{
  // set up the pin
  pinMode(ledPin, OUTPUT);
  // setup serial connection to the computer to read the sentence
  Serial.begin(9600);

}

void dot()
{
  Serial.print("DOT ");
  digitalWrite(ledPin, HIGH);
  delay(dotLength);
  digitalWrite(ledPin, LOW);
  delay(dotLength);
}

void dash()
{
  Serial.print("DASH ");
  digitalWrite(ledPin, HIGH);
  delay(3*dotLength);
  digitalWrite(ledPin, LOW);
  delay(dotLength);
}

void displayLetter(char letter)
{
  // 1. a dash is equal to 3 dots
  // 2. the space between parts of the same letter is eual to one dot
  // 3. the space between two letters is equal to three dots
  // 4. the space between 2 words is equal to 7 dots
  switch(letter)
  {
  case 'A':
    dot();
    dash();
    break;
  case 'B':
    break;
  case 'C':
    dash();
    dot();
    dash();
    dot();
    break;
  case 'D':
    dash();
    dot();
    dot();
    break;
  case 'E':
    dot();
    break;
  case 'F':
    dot();
    dot();
    dash();
    dot();
    break;
  case 'G':
    dash();
    dash();
    dot();
    break;
  case 'H':
    dot();
    dot();
    dot();
    dot();
    break;
  case 'I':
    dot();
    dot();
    break;
  case 'J':
    dot();
    dash();
    dash();
    dash();
    break;
  case 'K':
    dash();
    dot();
    dash();
    break;
  case 'L':
    dot();
    dash();
    dot();
    dot();
    break;
  case 'M':
    dash();
    dash();
    break;
  case 'N':
    dash();
    dot();
    break;
  case 'O':
    dash();
    dash();
    dash();
    break;
  case 'P':
    dot();
    dash();
    dash();
    dot();
    break;
  case 'Q':
    dash();
    dash();
    dot();
    dash();
    break;
  case 'R':
    dot();
    dash();
    dot();
    break;
  case 'S':
    dot();
    dot();
    dot();
    break;
  case 'T':
    dash();
    break;
  case 'U':
    dot();
    dot();
    dash();
    break;
  case 'V':
    dot();
    dot();
    dot();
    dash();
    break;
  case 'W':
    dot();
    dash();
    dash();
    break;
  case 'X':
    dash();
    dot();
    dot();
    dash();
    break;
  case 'Y':
    dash();
    dot();
    dash();
    dash();
    break;
  case 'Z':
    dash();
    dash();
    dot();
    dot();
    break;
  case ' ':
    // spaces will have 3 dots before it, and 2 dots after (from the pervious letter and the end of this letter) so the space will need 2
    extra dots to make a total of 7
      delay(2*dotLength);
    break;
  default:
    Serial.print("unknown letter [");
    Serial.print(letter);
    Serial.println("]");
  }
  delay(2*dotLength);// the space between letters is 3 dots but the end of the last part of the letter will have a 1 dot delay (to finish that letter) so
  e only do 2 dots here.

}

void loop()
{
  if(Serial.available())
  {
    counter = 0;
    while(Serial.available())
    {
      // get the new sentence
      sentence[counter] = Serial.read();
      if(sentence[counter] >= 'a' && sentence[counter] <= 'z')
      {
        sentence[counter] = sentence[counter] - 'a' + 'A';
      }
      if((sentence[counter] < 'A' || sentence[counter] > 'Z') && sentence[counter] != ' ')
      {
        Serial.println('non valid letter, replacing with space');
        sentence[counter] = ' ';
      }

      counter++;
      if(counter > 254)
      {
        // we have hit the limit of our sentence so abport
        Serial.println("Sentence is too long, ignoring the rest.");
        break;
      }
    }// end while we have available data on the serial port
    sentence[counter] = '\0';
    Serial.flush();
  }// end if
  // if there is nothing available (we havent gotten anything) then display the currect message
  // echo it out to the serial port
  Serial.print("Displaying code for: ");
  Serial.println(sentence);
  counter = 0;
  while(sentence[counter] != '\0')
  {
    Serial.print(sentence[counter]);
    Serial.print("- ");
    displayLetter(sentence[counter]);
    counter++;
  }
  Serial.println("\nEnd message");
  delay(500);
}

~(' ')~