SOS code by Mr S. Monk Page 71 sketch 5 - 02

Projects Programming
1

Hello,
I have found this code interesting because when I copied it from Mr S. Monks book & observed it work I was sure that it was not what I have experiences of what an SOS code ought to be.

So I slowed down the process so that I could watch the inbuilt led flash more easily, (example one below) I also deleted one of the 200 commands as written by Mr S. Monk.)

''{200, 200, 200, 500, 500, 500, 200, 200, 200}; ''

This line of command makes the Uno that I am using flash 4 times quickly, & not the allocated command of three quick flashes that is meant to represent S at the start of the code.
Then one sees three longer flashes to represent the O.
Finally, one experiences a different rate of flashes for the supposedly S at the end of the code that is meant to represent SOS!

Has any one observed similar results whilst experimenting with this code from Mr S. Monk?

Thank you
Dafyddclaud.

–---------------------------------------------------------------------------------------

// My modified code to prove a point.

int ledPin = 13;

int durations [] = {400, 400, 1000, 1000, 1000, 400, 400, 400,};

void setup ()
{
pinMode (ledPin, OUTPUT);
}

void loop ()
{
for (int i = 0; i < 9; i++)
{
flash (durations*);*

  • }*
  • delay (2000);*
    }
    void flash(int delayPeriod)
    {
  • digitalWrite(ledPin, HIGH);*
  • delay(delayPeriod);*
  • digitalWrite(ledPin, LOW);*
  • delay(delayPeriod);*
    }
    –----------------------------------------------------------------
    // S.Monk's sketch 5 – 02 from his web site & book.
    int ledPin = 13;
    int durations[] = {200, 200, 200, 500, 500, 500, 200, 200, 200};
    void setup()
    {
  • pinMode(ledPin, OUTPUT);*
    }
    void loop()
    {
  • for (int i = 0; i < 9; i++)*
  • {*
    _ flash(durations*);_
    _     }_
    _     delay(1000);_
    _    }_
    void flash(int duration)
    _    {_
    _     digitalWrite(ledPin, HIGH);_
    _     delay(duration);_
    _     digitalWrite(ledPin, LOW);_
    _     delay(duration);_
    _    }*_
2

You really need to edit that post, and put in the code tags you forgot.

// My modified code to prove a point.

All that code proves is that you can't count to nine.

3

Hi

Neither of those programs will flash correctly.

Firstly, when calling the flash() function, you need to access the array element:

for (int i = 0; i < 9; i++)
  {
    flash (durations[i]);
  }

Then, in your modified sketch, you need 9 durations, not 8:

int durations [] = {400, 400, 400, 1000, 1000, 1000, 400, 400, 400};

But there is also a problem with the flash() function in both programs. It turns the LED on for a given period, then turns it off for the same period. Morse code does not work like that. For the SOS prosign, the pattern should be:

@_@_@_@@@_@@@_@@@_@_@_@_____

where @ indicates LED on and _ is LED off.

The gaps between the dashes is the same as the gaps between the dots.

Regards

Ray

4

I just hate magic numbers in source code, so why not write the for loops and other statements that need the size of an array as:

#define ARRAYELEMENTS(x) (sizeof(x) / sizeof(x[0]))

// code to the first for loop...

   for (int i = 0; i < ARRAYELEMENTS(durations); i++) 
   {
// The rest of the code...

The advantage is that, if you change the size of an array, your for loops (and other code) that use the array size change automatically.