Simple If... Else... and Void with Serial input

Projects Programming
1

Hi all,

I'm trying to learn some of the basics using an If,,, Else,,, read/print from/to the serial monitor and a void.

My little sketch does not function how I'd imagine, when I run the program & open the serial monitor, if I enter "0" "1" "A" or any letter/ number it returns

You have entered Numeric One

Here is my sketch...

int userInput;

void setup()
{
  // initialize serial:
  Serial.begin(9600);
  Serial.println("Welcome");
  Serial.println("");
  Serial.println("Please enter 0 or 1");
  Serial.println("");
}

void loop()
{
  // if there's any serial available, read it:
  while (Serial.available() > 0)
  {
    userInput = Serial.read();

    if (userInput == 0 || 1)
    {
      valueEntered();
    }
    else
    {
      Serial.println("Input muck up, enter either 0 or 1");
    }
  }
}


void valueEntered()
{
  if (userInput == 0)
  {
    Serial.println("Your have entered Numeric Zero");
  }
  else
  {
    Serial.println("Your have entered Numeric One");
  }
}

I have tried changing int userInput; to char userInput; with better results but still not how I'd image it to behave.

char userInput;

void setup()
{
  // initialize serial:
  Serial.begin(9600);
  Serial.println("Welcome");
  Serial.println("");
  Serial.println("Please enter 0 or 1");
  Serial.println("");
}

void loop()
{
  // if there's any serial available, read it:
  while (Serial.available() > 0)
  {
    userInput = Serial.read();

    if (userInput == '0' || '1')
    {
      valueEntered();
    }
    else
    {
      Serial.println("Input muck up, enter either 0 or 1");
    }
  }
}


void valueEntered()
{
  if (userInput == '0')
  {
    Serial.println("Your have entered Numeric Zero");
  }
  else
  {
    Serial.println("Your have entered Numeric One");
  }
}

This time when I run the program, if I enter 0 into the serial monitor I get the reply

Your have entered Numeric Zero

and if I enter 1 into the serial monitor I get the reply

Your have entered Numeric One

but if I enter 3 or A into the serial monitor I get the reply

Your have entered Numeric One

My program doesn't appear to ever reach my Else, regardless of what invalid input I enter.

My question is... Why doesn't an invalid input trigger the Else in my program?

2 
    if (userInput == '0' || '1')

This is valid C/C++ but it isn't what you meant. It will never execute the else clause because '1' is non-zero.
Try:

    if (userInput == '0' || userInput == '1')

read/print from/to the serial monitor and a void

There's no such thing as "a void" in C/C++. There are functions which are declared to return nothing in which case the function name is preceded by the type "void".
So,

void loop() {

is a function named "loop". It doesn't return anything which is why the return type is specified as "void".

Pete

3

I'm trying to learn some of the basics using an If,,, Else,,, read/print from/to the serial monitor and a void.

If Ritchie had used the word "empty" instead of the unfortunate "void", your sentence would have read:

I'm trying to learn some of the basics using an If,,, Else,,, read/print from/to the serial monitor and an empty.

4

Now my little program works, thank-you Pete for your help and explanation. I couldn't think what else to call the "void", in Visual basics I believe it would have been called a "Sub Routine"

Many thanks,

Skippy.

5

"Sub Routine" is far closer to "function" than "void".

-jim lee