Bolean false and serial println

Using Arduino Programming Questions
#1

Hello,

When I tried to run serial printf on the bolean function below, if the state is false, the output isn’t printing 0 but instead some random number. But, when the state is one, 1 is been printed. The bauld rate has been set to 9600.

This program suppose to read input from a motion sensor.

boolean sensor(){
Serial.begin (9600);
digitalRead (_sensorPin);
boolean state = true;

if (!digitalRead (_sensorPin)== HIGH){
boolean state = false;
}

Serial.println (state);
return state;
}

BooleanTrue.PNG
BooleanTrue.PNG1698×732 27.3 KB

BooleanFalse.PNG
BooleanFalse.PNG1690×760 28.4 KB

#2

You have two state variables.
Why?

Please remember to use code tags when posting code

#3

TheMemberFormerlyKnownAsAWOL:
You have two state variables.
Why?

Please remember to use code tags when posting code

Thanks for your reply.
what do you mean by two state variables?

#4

You have defined two variables called “state”, the second of which has very limited scope.

I also suspect you don’t want Serial.begin in your function.

#5

TheMemberFormerlyKnownAsAWOL:
You have defined two variables called "state", the second of which has very limited scope.

I also suspect you don't want Serial.begin in your function.

I thought it is only one variable that I have set to true and then false.

#6 
boolean sensor(){
      Serial.begin (9600);
      digitalRead (_sensorPin);
      boolean state = true; <<< one variable here
   
      if (!digitalRead (_sensorPin)== HIGH){
      boolean  state  = false;  <<< another variable here
      }

     
      Serial.println (state);
      return state;
    }
#7

Also, if you’re not doing anything with the result of the first digitalRead, you should make it clear to readers (void)digitalRead (_sensorPin);

You can assign booleans directly boolean state = digitalRead (_sensorPin) == HIGH;

#8

Thank you so much.
This line of code has solved my issue.

boolean state = digitalRead (_sensorPin) == HIGH;

At least I have learned to define the state variable only 1 time.

#9

Hi,
What do you expect this line to do?

   digitalRead (_sensorPin);

This may help;
https://www.arduino.cc/reference/en/language/functions/digital-io/digitalread/

Tom... :slight_smile:

#10

TomGeorge:
Hi,
What do you expect this line to do?

   digitalRead (_sensorPin);

This may help;
digitalRead() - Arduino Reference

Tom… :slight_smile:

See reply #6

#11