Program ignores while-loop

Projects Programming
1

Hello everyone!
I don't know why but my Arduino Testprogram does not work like it should:

void setup() {
  Serial.begin(9600);
  pinMode(LED1,OUTPUT);
  pinMode(LED2,OUTPUT);

  Serial.println("Number of LED1 blinks? ");
  while (Serial.available()==0){}
  b1 = Serial.parseInt();

  Serial.println("Number of LED2 blinks? ");
  while (Serial.available()==0){}
  b2 = Serial.parseInt();

It is just a test where I am asking in the serial monitor for an input.
What now happens is, that there is the first question: "Number of LED1 blinks?"
after the Input, the second question appears and shortly after the program starts (the void loop) without waiting for the input :frowning:

The second while loop does not work somehow...

2

This works for me on a Leonardo :

void setup() {
  Serial.begin(115200);
  while (!Serial);  //  <-- For Leonardo

  Serial.println("Number of LED1 blinks? ");
  while (Serial.available() == 0) {}
  int b1 = Serial.parseInt();
  Serial.println(b1);

  Serial.println("Number of LED2 blinks? ");
  while (Serial.available() == 0) {}
  int b2 = Serial.parseInt();
  Serial.println(b2);
}

void loop() {
}

Serial monitor displays:

10:07:56.350 -> Number of LED1 blinks?
10:07:58.429 -> 11
10:07:58.429 -> Number of LED2 blinks?
10:07:59.410 -> 20

What is your board?

3

I'm going to guess you have the monitor's line ending set to something other than no line end, so the presence of line end character/s is making it fail the second test.

line end and baud.GIF

4

My setting here is indeed "newline", but the other settings give the same result

5

Well I did a quick test and it works fine with "no line ending", and gives your OP's symptom with any other.

6

lesept:
My setting here is indeed "newline", but the other settings give the same result

Sorry, I thought that reply was from OP.

OP's code works for me on Uno with no line ending, but gives OP's symptom with the others.

Something to do with Leonardo's USB?

7

Your line ending in the Serial Monitor is set to "Both NL & CR" (or you send more then just numbers when you send you input (including spaces). parseInt() breaks on the NL (new line) but that leaves the CR in the buffer.

Damnit, I forgot to hit post...

8

I ran this code:

byte LED1=2;
byte LED2=3;

void setup() 
{
  Serial.begin(9600);
  pinMode(LED1,OUTPUT);
  pinMode(LED2,OUTPUT);
  Serial.println("start");

  Serial.println("Number of LED1 blinks? ");
  while (Serial.available()==0){}
  int b1 = Serial.parseInt();
  Serial.println(b1);
  

  Serial.println("Number of LED2 blinks? ");
  while (Serial.available()==0){}
  int b2 = Serial.parseInt();
  Serial.println(b2);
  Serial.println("end");

}
void loop(){}

And here are my serial spews:

start
Number of LED1 blinks? 
5
Number of LED2 blinks? 
3
end

start
Number of LED1 blinks? 
5
Number of LED2 blinks? 
0
end

start
Number of LED1 blinks? 
5
Number of LED2 blinks? 
0
end

start
Number of LED1 blinks? 
5
Number of LED2 blinks? 
0
end

Only the first one waits for input (the 3), the others fly right through and print the b2's initialised value (the 0).

9

Thank you guys! Now it is working.
With Newline it does not work - with no line ending it does :slight_smile:

But what happens here? I work with an Arduino Mega2560.

10

Erazor85:
But what happens here?

The line end character/s which are the flags that your integer has ended, are also characters in their own right so they count towards the second "while (Serial.available()==0)" test not being 0, even though you only typed one key.

In other news, it may be important to you one day that Serial.parseInt() is a blocking function. You may have noticed a lag in your example until the timeout kicked in; I did.

If it matters one day, eg where the responsiveness of buttons is crucial, it would behoove you to read Robin2's serial tutorial.

11

Okay, thank you for the information - sounds logic :slight_smile: