ISR best practices in Arduino - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to attach an interrupt service routine (ISR) to pin 2 on a rising edge.

Arduino

attachInterrupt(digitalPinToInterrupt(2), [1], RISING);

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AinterruptHandler

BonInterrupt

CISR

DhandleInterrupt

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function name that is not defined.

Passing the ISR function with parentheses (e.g., interruptHandler()).

The function interruptHandler is the ISR attached to the interrupt on pin 2.

2fill in blank

medium

Complete the ISR function to set a flag variable buttonPressed to true.

Arduino

volatile bool buttonPressed = false;

void [1]() {
  buttonPressed = true;
}

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AISR

BhandleButton

CbuttonISR

DinterruptHandler

Attempts:

3 left

💡 Hint

Common Mistakes

Not declaring the flag variable as volatile.

Using a function name different from the one attached to the interrupt.

The ISR function buttonISR sets the flag buttonPressed to true when called.

3fill in blank

hard

Fix the error in the ISR by removing the disallowed function call inside it.

Arduino

void buttonISR() {
  [1];
}

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ASerial.println("Pressed")

BbuttonPressed = true

Cdelay(100)

DdigitalWrite(LED_BUILTIN, HIGH)

Attempts:

3 left

💡 Hint

Common Mistakes

Calling Serial.println inside ISR causing unexpected behavior.

Using delay inside ISR which blocks execution.

Inside an ISR, avoid functions like Serial.println or delay. Setting a flag is safe.

4fill in blank

hard

Fill both blanks to safely check and reset the flag buttonPressed in the main loop.

Arduino

void loop() {
  if ([1]) {
    [2] = false;
    // Handle button press here
  }
}

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AbuttonPressed

CbuttonPressed == true

DbuttonPressed == false

Attempts:

3 left

💡 Hint

Common Mistakes

Using assignment = instead of comparison == in the if condition.

Not resetting the flag after handling.

Check if buttonPressed is true, then reset it to false after handling.

5fill in blank

hard

Fill all three blanks to declare a volatile flag, attach the ISR, and handle the flag in the loop.

Arduino

volatile bool [1] = false;

void setup() {
  pinMode(2, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(2), [2], FALLING);
}

void loop() {
  if ([3]) {
    [1] = false;
    // Respond to interrupt
  }
}

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AbuttonPressed

BbuttonISR

DinterruptHandler

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the flag variable in declaration and loop.

Mismatching ISR function names between declaration and attachInterrupt.

The flag buttonPressed is declared volatile, the ISR buttonISR is attached, and the flag is checked and reset in the loop.