Revisions to How to update a variable in an ISR using Timers

Solutions added

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edited Dec 11, 2014 at 22:54

UserK

559
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EDIT2SOLUTION 1 I've commented the line cont=0; in the if statement and I get the following output.Thanks to Gerben

Setupvolatile completedint cont = 0;

void ticksetup()
{
  Serial.begin(9600);
  pinMode(13, OUTPUT);

  // Initialize Timer
  cli();          // disable global interrupts
  TCCR3A = 0;     // set entire TCCR3A register to 0
  TCCR3B = 0;     // same for TCCR3B

  // set compare match register to desired timer count: 1800 Hz
  OCR3A = 20; // First20; output//800Hz 5; // 3 Hz
 tick // turn on CTC mode:
  TCCR3B |= (1 << WGM32);
 tick // Set CS10 and CS12 bits for 1024 prescaler:
  TCCR3B |= (1 << CS30) | (1 << CS32);
 tick // enable timer compare interrupt:
  TIMSK3 |= (1 << OCIE3B);
  // Secondenable global interrupts:
 tick sei();
  Serial.println("Setup completed");
}

void loop()
{
  delay(1000);
  Serial.println(cont);
  cont = 0;
}

ISR(TIMER3_COMPB_vect)
{
  cont++;
}

SOLUTION 2 Thanks to BrettM

volatile int cont = 0;

void setup()
{
  Serial.begin(9600);
  pinMode(13, OUTPUT);

  // Initialize Timer
  cli();          // disable global interrupts
  TCCR3A = 0;     // set entire TCCR3A register to 0
  TCCR3B = 0;     // same for TCCR3B

  // set compare match register to desired timer count: 1800 Hz
 tick OCR3B =  20; //800Hz 5; // 3 Hz
  // turn on CTC mode:
  //TCCR3B |= (1 << WGM32);
 tick // Set CS10 and CS12 bits for 1024 prescaler:
  TCCR3B |= (1 << CS30) | (1 << CS32);
  // Third
enable ticktimer compare interrupt:
  TIMSK3 |= (1 << OCIE3B);
 tick // enable global interrupts: 
 1 sei();
  Serial.println("Setup completed");
}

void loop()
{
  Serial.println(cont); 
  cont = 0;
  delay(1000);
  
}

ISR(TIMER3_COMPB_vect)
{
  TCNT3 = 0;
  cont++;
}

I don't know why the if statement prints 3 lines instead of one.

EDIT2 I've commented the line cont=0; in the if statement and I get the following output.

Setup completed
 tick: 1  // First output
 tick: 1 
 tick: 1  
 tick: 1  // Second 
 tick: 1
 tick: 1
 tick: 1  // Third
 tick: 1
 tick: 1

I don't know why the if statement prints 3 lines instead of one.

SOLUTION 1 Thanks to Gerben

volatile int cont = 0;

void setup()
{
  Serial.begin(9600);
  pinMode(13, OUTPUT);

  // Initialize Timer
  cli();          // disable global interrupts
  TCCR3A = 0;     // set entire TCCR3A register to 0
  TCCR3B = 0;     // same for TCCR3B

  // set compare match register to desired timer count: 800 Hz
  OCR3A = 20; // 20; //800Hz 5; // 3 Hz
  // turn on CTC mode:
  TCCR3B |= (1 << WGM32);
  // Set CS10 and CS12 bits for 1024 prescaler:
  TCCR3B |= (1 << CS30) | (1 << CS32);
  // enable timer compare interrupt:
  TIMSK3 |= (1 << OCIE3B);
  // enable global interrupts:
  sei();
  Serial.println("Setup completed");
}

void loop()
{
  delay(1000);
  Serial.println(cont);
  cont = 0;
}

ISR(TIMER3_COMPB_vect)
{
  cont++;
}

SOLUTION 2 Thanks to BrettM

volatile int cont = 0;

void setup()
{
  Serial.begin(9600);
  pinMode(13, OUTPUT);

  // Initialize Timer
  cli();          // disable global interrupts
  TCCR3A = 0;     // set entire TCCR3A register to 0
  TCCR3B = 0;     // same for TCCR3B

  // set compare match register to desired timer count: 800 Hz
  OCR3B =  20; //800Hz 5; // 3 Hz
  // turn on CTC mode:
  //TCCR3B |= (1 << WGM32);
  // Set CS10 and CS12 bits for 1024 prescaler:
  TCCR3B |= (1 << CS30) | (1 << CS32);
  // enable timer compare interrupt:
  TIMSK3 |= (1 << OCIE3B);
  // enable global interrupts: 
  sei();
  Serial.println("Setup completed");
}

void loop()
{
  Serial.println(cont); 
  cont = 0;
  delay(1000);
  
}

ISR(TIMER3_COMPB_vect)
{
  TCNT3 = 0;
  cont++;
}

Pointed out he issue and clarified the meaning

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edited Dec 11, 2014 at 12:42

UserK

559
1
11
24

I'm trying to check the frequency of Timer3 using a counter. The value of the counter, declared as volatile, is incremented in the ISR and every second the sum is shown in the main loop and the value reset to zero.

The timer has been set up correctly. (If I choose a 3Hz timer I can see the led blinking)

The problem

The counter isn't incremented. Here is the output:

Setup Completed
tick: 1
tick: 0
tick: 0
tick: 0

CODE

volatile int cont = 0;

void setup()
{
  Serial.begin(9600);
  
  pinMode(13, OUTPUT);

  // Initialize Timer
  cli();          // disable global interrupts
  TCCR3A = 0;     // set entire TCCR3A register to 0
  TCCR3B = 0;     // same for TCCR3B
 
  // set compare match register to desired timer count: 800 Hz
  OCR3B = 20; // 800Hz 5; // 3 Hz
  // turn on CTC mode:
  TCCR3B |= (1 << WGM12);
  // Set CS10 and CS12 bits for 1024 prescaler:
  TCCR3B |= (1 << CS30) | (1 << CS32);
  // enable timer compare interrupt:
  TIMSK3 |= (1 << OCIE3B);
  // enable global interrupts:
  sei();
  
  Serial.println("Setup completed");
}

void loop()
{
  if (millis() % 1000 == 0)
  {
    Serial.print(" tick: ");
    Serial.println(cont);
    cont = 0;
  }
}

ISR(TIMER3_COMPB_vect)
{
  //digitalWrite(13, digitalRead(13) ^ 1);
  cont++;
}

The problem

The counter isn't incremented. Here is the output:

Setup Completed
tick: 1
tick: 0
tick: 0
tick: 0

EDIT This timer is used to read an anlog value from an accelerometer and store it in an array of float. But at the moment I'm stuck on this update issue.

EDIT2 I've commented the line cont=0; in the if statement and I get the following output.

Setup completed
 tick: 1  // First output
 tick: 1 
 tick: 1  
 tick: 1  // Second 
 tick: 1
 tick: 1
 tick: 1  // Third
 tick: 1
 tick: 1

I don't know why the if statement prints 3 lines instead of one.

I'm trying to check the frequency of Timer3 using a counter. The value of the counter, declared as volatile, is incremented in the ISR and every second the sum is shown in the main loop and the value reset to zero.

The timer has been set up correctly. (If I choose a 3Hz timer I can see the led blinking)

CODE

volatile int cont = 0;

void setup()
{
  Serial.begin(9600);
  
  pinMode(13, OUTPUT);

  // Initialize Timer
  cli();          // disable global interrupts
  TCCR3A = 0;     // set entire TCCR3A register to 0
  TCCR3B = 0;     // same for TCCR3B
 
  // set compare match register to desired timer count: 800 Hz
  OCR3B = 20; // 800Hz 5; // 3 Hz
  // turn on CTC mode:
  TCCR3B |= (1 << WGM12);
  // Set CS10 and CS12 bits for 1024 prescaler:
  TCCR3B |= (1 << CS30) | (1 << CS32);
  // enable timer compare interrupt:
  TIMSK3 |= (1 << OCIE3B);
  // enable global interrupts:
  sei();
  
  Serial.println("Setup completed");
}

void loop()
{
  if (millis() % 1000 == 0)
  {
    Serial.print(" tick: ");
    Serial.println(cont);
    cont = 0;
  }
}

ISR(TIMER3_COMPB_vect)
{
  //digitalWrite(13, digitalRead(13) ^ 1);
  cont++;
}

The problem

The counter isn't incremented. Here is the output:

Setup Completed
tick: 1
tick: 0
tick: 0
tick: 0

EDIT This timer is used to read an anlog value from an accelerometer and store it in an array of float. But at the moment I'm stuck on this update issue.

EDIT2 I've commented the line cont=0; in the if statement and I get the following output.

Setup completed
 tick: 1  // First output
 tick: 1 
 tick: 1  
 tick: 1  // Second 
 tick: 1
 tick: 1
 tick: 1  // Third
 tick: 1
 tick: 1

I don't know why the if statement prints 3 lines instead of one.

I'm trying to check the frequency of Timer3 using a counter. The value of the counter, declared as volatile, is incremented in the ISR and every second the sum is shown in the main loop and the value reset to zero.

The timer has been set up correctly. (If I choose a 3Hz timer I can see the led blinking)

The problem

The counter isn't incremented. Here is the output:

Setup Completed
tick: 1
tick: 0
tick: 0
tick: 0

CODE

volatile int cont = 0;

void setup()
{
  Serial.begin(9600);
  
  pinMode(13, OUTPUT);

  // Initialize Timer
  cli();          // disable global interrupts
  TCCR3A = 0;     // set entire TCCR3A register to 0
  TCCR3B = 0;     // same for TCCR3B
 
  // set compare match register to desired timer count: 800 Hz
  OCR3B = 20; // 800Hz 5; // 3 Hz
  // turn on CTC mode:
  TCCR3B |= (1 << WGM12);
  // Set CS10 and CS12 bits for 1024 prescaler:
  TCCR3B |= (1 << CS30) | (1 << CS32);
  // enable timer compare interrupt:
  TIMSK3 |= (1 << OCIE3B);
  // enable global interrupts:
  sei();
  
  Serial.println("Setup completed");
}

void loop()
{
  if (millis() % 1000 == 0)
  {
    Serial.print(" tick: ");
    Serial.println(cont);
    cont = 0;
  }
}

ISR(TIMER3_COMPB_vect)
{
  //digitalWrite(13, digitalRead(13) ^ 1);
  cont++;
}

EDIT This timer is used to read an anlog value from an accelerometer and store it in an array of float. But at the moment I'm stuck on this update issue.

EDIT2 I've commented the line cont=0; in the if statement and I get the following output.

Setup completed
 tick: 1  // First output
 tick: 1 
 tick: 1  
 tick: 1  // Second 
 tick: 1
 tick: 1
 tick: 1  // Third
 tick: 1
 tick: 1

I don't know why the if statement prints 3 lines instead of one.

added 358 characters in body

Source Link

edited Dec 11, 2014 at 12:13

UserK

559
1
11
24

I'm trying to check the frequency of Timer3 using a counter. The value of the counter, declared as volatile, is incremented in the ISR and every second the sum is shown in the main loop and the value reset to zero.

The timer has been set up correctly. (If I choose a 3Hz timer I can see the led blinking)

CODE

volatile int cont = 0;

void setup()
{
  Serial.begin(9600);
  
  pinMode(13, OUTPUT);

  // Initialize Timer
  cli();          // disable global interrupts
  TCCR3A = 0;     // set entire TCCR3A register to 0
  TCCR3B = 0;     // same for TCCR3B
 
  // set compare match register to desired timer count: 800 Hz
  OCR3B = 20; // 800Hz 5; // 3 Hz
  // turn on CTC mode:
  TCCR3B |= (1 << WGM12);
  // Set CS10 and CS12 bits for 1024 prescaler:
  TCCR3B |= (1 << CS30) | (1 << CS32);
  // enable timer compare interrupt:
  TIMSK3 |= (1 << OCIE3B);
  // enable global interrupts:
  sei();
  
  Serial.println("Setup completed");
}

void loop()
{
  if (millis() % 1000 == 0)
  {
    Serial.print(" tick: ");
    Serial.println(cont);
    cont = 0;
  }
}

ISR(TIMER3_COMPB_vect)
{
  //digitalWrite(13, digitalRead(13) ^ 1);
  cont++;
}

The problem

The counter isn't incremented. Here is the output:

Setup Completed
tick: 1
tick: 0
tick: 0
tick: 0

EDIT This timer is used to read an anlog value from an accelerometer and store it in an array of float. But at the moment I'm stuck on this update issue.

EDIT2 I've commented the line cont=0; in the if statement and I get the following output.

Setup completed
 tick: 1  // First output
 tick: 1 
 tick: 1  
 tick: 1  // Second 
 tick: 1
 tick: 1
 tick: 1  // Third
 tick: 1
 tick: 1

I don't know why the if statement prints 3 lines instead of one.

I'm trying to check the frequency of Timer3 using a counter. The value of the counter, declared as volatile, is incremented in the ISR and every second the sum is shown in the main loop and the value reset to zero.

The timer has been set up correctly. (If I choose a 3Hz timer I can see the led blinking)

CODE

volatile int cont = 0;

void setup()
{
  Serial.begin(9600);
  
  pinMode(13, OUTPUT);

  // Initialize Timer
  cli();          // disable global interrupts
  TCCR3A = 0;     // set entire TCCR3A register to 0
  TCCR3B = 0;     // same for TCCR3B
 
  // set compare match register to desired timer count: 800 Hz
  OCR3B = 20; // 800Hz 5; // 3 Hz
  // turn on CTC mode:
  TCCR3B |= (1 << WGM12);
  // Set CS10 and CS12 bits for 1024 prescaler:
  TCCR3B |= (1 << CS30) | (1 << CS32);
  // enable timer compare interrupt:
  TIMSK3 |= (1 << OCIE3B);
  // enable global interrupts:
  sei();
  
  Serial.println("Setup completed");
}

void loop()
{
  if (millis() % 1000 == 0)
  {
    Serial.print(" tick: ");
    Serial.println(cont);
    cont = 0;
  }
}

ISR(TIMER3_COMPB_vect)
{
  //digitalWrite(13, digitalRead(13) ^ 1);
  cont++;
}

The problem

The counter isn't incremented. Here is the output:

Setup Completed
tick: 1
tick: 0
tick: 0
tick: 0

EDIT This timer is used to read an anlog value from an accelerometer and store it in an array of float. But at the moment I'm stuck on this update issue.

I'm trying to check the frequency of Timer3 using a counter. The value of the counter, declared as volatile, is incremented in the ISR and every second the sum is shown in the main loop and the value reset to zero.

The timer has been set up correctly. (If I choose a 3Hz timer I can see the led blinking)

CODE

volatile int cont = 0;

void setup()
{
  Serial.begin(9600);
  
  pinMode(13, OUTPUT);

  // Initialize Timer
  cli();          // disable global interrupts
  TCCR3A = 0;     // set entire TCCR3A register to 0
  TCCR3B = 0;     // same for TCCR3B
 
  // set compare match register to desired timer count: 800 Hz
  OCR3B = 20; // 800Hz 5; // 3 Hz
  // turn on CTC mode:
  TCCR3B |= (1 << WGM12);
  // Set CS10 and CS12 bits for 1024 prescaler:
  TCCR3B |= (1 << CS30) | (1 << CS32);
  // enable timer compare interrupt:
  TIMSK3 |= (1 << OCIE3B);
  // enable global interrupts:
  sei();
  
  Serial.println("Setup completed");
}

void loop()
{
  if (millis() % 1000 == 0)
  {
    Serial.print(" tick: ");
    Serial.println(cont);
    cont = 0;
  }
}

ISR(TIMER3_COMPB_vect)
{
  //digitalWrite(13, digitalRead(13) ^ 1);
  cont++;
}

The problem

The counter isn't incremented. Here is the output:

Setup Completed
tick: 1
tick: 0
tick: 0
tick: 0

EDIT This timer is used to read an anlog value from an accelerometer and store it in an array of float. But at the moment I'm stuck on this update issue.

EDIT2 I've commented the line cont=0; in the if statement and I get the following output.

Setup completed
 tick: 1  // First output
 tick: 1 
 tick: 1  
 tick: 1  // Second 
 tick: 1
 tick: 1
 tick: 1  // Third
 tick: 1
 tick: 1

I don't know why the if statement prints 3 lines instead of one.

deleted 4 characters in body

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edited Dec 11, 2014 at 11:54

UserK

559
1
11
24

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added 158 characters in body

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edited Dec 11, 2014 at 11:48

UserK

559
1
11
24

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Tweeted twitter.com/#!/StackArduino/status/542918135876448257

occurred Dec 11, 2014 at 5:45

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asked Dec 11, 2014 at 0:03

UserK

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1
11
24

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