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Topic: Problem with my serial monitor (Read 1 time) previous topic - next topic

GabyC89


Quote
So, what do you sugest?
Where should I put a delay?


Delay() is rarely the best method of handling timing situations. You need to keep a flag variable of the last state of the digitalRead() command and then when you read it again you compare it to the flag value, if they are the same then nothing changed, if they are different then there was a state change with the button and you then update the flag variable for the next time you check the input pin as well as perform the task you need to do because of the state change.

Lefty


Can you put a simple code example, please?

retrolefty



Quote
So, what do you sugest?
Where should I put a delay?


Delay() is rarely the best method of handling timing situations. You need to keep a flag variable of the last state of the digitalRead() command and then when you read it again you compare it to the flag value, if they are the same then nothing changed, if they are different then there was a state change with the button and you then update the flag variable for the next time you check the input pin as well as perform the task you need to do because of the state change.

Lefty


Can you put a simple code example, please?


The Arduino people already gave you an example called StateChageDetection in the files/example/Digital example sketches, but I'll post it here:


Code: [Select]

/*
  State change detection (edge detection)

Often, you don't need to know the state of a digital input all the time,
but you just need to know when the input changes from one state to another.
For example, you want to know when a button goes from OFF to ON.  This is called
state change detection, or edge detection.

This example shows how to detect when a button or button changes from off to on
and on to off.

The circuit:
* pushbutton attached to pin 2 from +5V
* 10K resistor attached to pin 2 from ground
* LED attached from pin 13 to ground (or use the built-in LED on
   most Arduino boards)

created  27 Sep 2005
modified 30 Aug 2011
by Tom Igoe

This example code is in the public domain.

http://arduino.cc/en/Tutorial/ButtonStateChange

*/

// this constant won't change:
const int  buttonPin = 2;    // the pin that the pushbutton is attached to
const int ledPin = 13;       // the pin that the LED is attached to

// Variables will change:
int buttonPushCounter = 0;   // counter for the number of button presses
int buttonState = 0;         // current state of the button
int lastButtonState = 0;     // previous state of the button

void setup() {
  // initialize the button pin as a input:
  pinMode(buttonPin, INPUT);
  // initialize the LED as an output:
  pinMode(ledPin, OUTPUT);
  // initialize serial communication:
  Serial.begin(9600);
}


void loop() {
  // read the pushbutton input pin:
  buttonState = digitalRead(buttonPin);

  // compare the buttonState to its previous state
  if (buttonState != lastButtonState) {
    // if the state has changed, increment the counter
    if (buttonState == HIGH) {
      // if the current state is HIGH then the button
      // wend from off to on:
      buttonPushCounter++;
      Serial.println("on");
      Serial.print("number of button pushes:  ");
      Serial.println(buttonPushCounter);
    }
    else {
      // if the current state is LOW then the button
      // wend from on to off:
      Serial.println("off");
    }
  }
  // save the current state as the last state,
  //for next time through the loop
  lastButtonState = buttonState;

 
  // turns on the LED every four button pushes by
  // checking the modulo of the button push counter.
  // the modulo function gives you the remainder of
  // the division of two numbers:
  if (buttonPushCounter % 4 == 0) {
    digitalWrite(ledPin, HIGH);
  } else {
   digitalWrite(ledPin, LOW);
  }
 
}


Good luck with your project.

Lefty

GabyC89




Quote
So, what do you sugest?
Where should I put a delay?


Delay() is rarely the best method of handling timing situations. You need to keep a flag variable of the last state of the digitalRead() command and then when you read it again you compare it to the flag value, if they are the same then nothing changed, if they are different then there was a state change with the button and you then update the flag variable for the next time you check the input pin as well as perform the task you need to do because of the state change.

Lefty


Can you put a simple code example, please?


The Arduino people already gave you an example called StateChageDetection in the files/example/Digital example sketches, but I'll post it here:


Code: [Select]

/*
  State change detection (edge detection)

Often, you don't need to know the state of a digital input all the time,
but you just need to know when the input changes from one state to another.
For example, you want to know when a button goes from OFF to ON.  This is called
state change detection, or edge detection.

This example shows how to detect when a button or button changes from off to on
and on to off.

The circuit:
* pushbutton attached to pin 2 from +5V
* 10K resistor attached to pin 2 from ground
* LED attached from pin 13 to ground (or use the built-in LED on
   most Arduino boards)

created  27 Sep 2005
modified 30 Aug 2011
by Tom Igoe

This example code is in the public domain.

http://arduino.cc/en/Tutorial/ButtonStateChange

*/

// this constant won't change:
const int  buttonPin = 2;    // the pin that the pushbutton is attached to
const int ledPin = 13;       // the pin that the LED is attached to

// Variables will change:
int buttonPushCounter = 0;   // counter for the number of button presses
int buttonState = 0;         // current state of the button
int lastButtonState = 0;     // previous state of the button

void setup() {
  // initialize the button pin as a input:
  pinMode(buttonPin, INPUT);
  // initialize the LED as an output:
  pinMode(ledPin, OUTPUT);
  // initialize serial communication:
  Serial.begin(9600);
}


void loop() {
  // read the pushbutton input pin:
  buttonState = digitalRead(buttonPin);

  // compare the buttonState to its previous state
  if (buttonState != lastButtonState) {
    // if the state has changed, increment the counter
    if (buttonState == HIGH) {
      // if the current state is HIGH then the button
      // wend from off to on:
      buttonPushCounter++;
      Serial.println("on");
      Serial.print("number of button pushes:  ");
      Serial.println(buttonPushCounter);
    }
    else {
      // if the current state is LOW then the button
      // wend from on to off:
      Serial.println("off");
    }
  }
  // save the current state as the last state,
  //for next time through the loop
  lastButtonState = buttonState;

 
  // turns on the LED every four button pushes by
  // checking the modulo of the button push counter.
  // the modulo function gives you the remainder of
  // the division of two numbers:
  if (buttonPushCounter % 4 == 0) {
    digitalWrite(ledPin, HIGH);
  } else {
   digitalWrite(ledPin, LOW);
  }
 
}


Good luck with your project.

Lefty


OK, thanks, I'll see if they solve my problem.
Thank you for your preoccupation and help.

PaulS

Code: [Select]
  if ( digitalRead(0) == HIGH )
  {
      // flanco descendente
      if ( digitalRead(0) == LOW )
      {

Pin 0 is one half of the Serial pins. You can't use pin 0 or 1 for a switch, too.

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