Blink without delay pattern in Arduino - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the LED pin as output in setup().

Arduino

void setup() {
  pinMode([1], OUTPUT);
}

void loop() {
  // blinking code here
}

Drag options to blanks, or click blank then click option'

A13

B12

C10

DLED_BUILTIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using a pin number directly without knowing if it matches the built-in LED.

Forgetting to set the pin mode to OUTPUT.

The built-in LED pin is usually defined as LED_BUILTIN, which is pin 13 on most Arduino boards.

2fill in blank

medium

Complete the code to get the current time in milliseconds inside loop().

Arduino

void loop() {
  unsigned long currentMillis = [1]();
  // rest of the code
}

Drag options to blanks, or click blank then click option'

Amillis

Bdelay

Cmicros

Dtime

Attempts:

3 left

💡 Hint

Common Mistakes

Using delay() which pauses the program.

Using micros() which returns microseconds, not milliseconds.

The millis() function returns the number of milliseconds since the Arduino started running the current program.

3fill in blank

hard

Fix the error in the if condition to check if the interval has passed.

Arduino

if (currentMillis - previousMillis [1] interval) {
  // toggle LED
}

Drag options to blanks, or click blank then click option'

A<

B>=

C==

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' which triggers too early.

Using '==' which may miss the exact match.

We check if the time difference is greater than or equal to the interval to know when to toggle the LED.

4fill in blank

hard

Fill both blanks to toggle the LED state and update previousMillis.

Arduino

if (ledState == LOW) {
  ledState = [1];
} else {
  ledState = [2];
}
previousMillis = currentMillis;

Drag options to blanks, or click blank then click option'

AHIGH

BLOW

Ctrue

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using boolean true/false instead of HIGH/LOW.

Setting both states to the same value.

If the LED is off (LOW), turn it on (HIGH). Otherwise, turn it off (LOW).

5fill in blank

hard

Fill all three blanks to complete the blink without delay pattern code.

Arduino

const int ledPin = [1];
unsigned long previousMillis = 0;
const long interval = [2];
int ledState = LOW;

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  unsigned long currentMillis = [3]();
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
    if (ledState == LOW) {
      ledState = HIGH;
    } else {
      ledState = LOW;
    }
    digitalWrite(ledPin, ledState);
  }
}

Drag options to blanks, or click blank then click option'

ALED_BUILTIN

B1000

Cmillis

D13

Attempts:

3 left

💡 Hint

Common Mistakes

Using delay() instead of millis().

Using wrong pin number instead of LED_BUILTIN.

Setting interval to 1 instead of 1000.

Use LED_BUILTIN for the built-in LED pin, 1000 milliseconds for 1 second interval, and millis() to get current time.

Practice

1. What is the main advantage of using the Blink without delay pattern in Arduino programming?

easy

A. It allows the Arduino to perform other tasks while blinking an LED.

B. It makes the LED blink faster than usual.

C. It uses less power than the delay() function.

D. It requires fewer lines of code than delay().

Solution

1. Step 1: Understand delay() limitation

   The delay() function pauses the whole program, stopping other tasks.

2. Step 2: millis() allows multitasking

   Using millis() tracks time without stopping the program, so other code runs simultaneously.

3. Final Answer:

   It allows the Arduino to perform other tasks while blinking an LED. -> Option A

4. Quick Check:

   Blink without delay = multitasking [OK]

Hint: Remember millis() tracks time without stopping code [OK]

Common Mistakes:

• Thinking delay() lets other code run
• Believing blink speed is faster with millis()
• Assuming millis() uses less power

2. Which of the following code snippets correctly initializes the variable to store the last time the LED was toggled in the Blink without delay pattern?

easy

A. unsigned long previousMillis = 0;

B. int previousMillis = 0;

C. float previousMillis = 0.0;

D. boolean previousMillis = false;

Solution

1. Step 1: Identify correct data type for millis()

   millis() returns an unsigned long value representing milliseconds.

2. Step 2: Match variable type to millis()

   To store millis() values, use unsigned long to avoid overflow and negative values.

3. Final Answer:

   unsigned long previousMillis = 0; -> Option A

4. Quick Check:

   Use unsigned long for time tracking [OK]

Hint: Use unsigned long for millis() time variables [OK]

Common Mistakes:

• Using int which can overflow quickly
• Using float which is unnecessary and imprecise
• Using boolean which can't store time

3. What will be the output behavior of the following Arduino code snippet using Blink without delay pattern?

const int ledPin = 13;
unsigned long previousMillis = 0;
const long interval = 1000;
bool ledState = false;

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
    ledState = !ledState;
    digitalWrite(ledPin, ledState ? HIGH : LOW);
  }
}

medium

A. The LED will blink rapidly without delay.

B. The LED on pin 13 will blink on and off every 1 second without stopping other code.

C. The LED will stay on permanently after 1 second.

D. The program will cause a compile error due to bool type.

Solution

1. Step 1: Analyze timing logic

   The code checks if 1000 ms passed since last toggle, then flips ledState.

2. Step 2: Understand LED toggle and output

   ledState toggles true/false every second, controlling LED on/off without delay blocking.

3. Final Answer:

   The LED on pin 13 will blink on and off every 1 second without stopping other code. -> Option B

4. Quick Check:

   Millis timing toggles LED every 1 second [OK]

Hint: Look for millis() interval check to predict blink timing [OK]

Common Mistakes:

• Thinking bool causes compile error
• Assuming LED stays on permanently
• Confusing rapid blinking with 1-second interval

4. Identify the error in this Blink without delay code snippet:

const int ledPin = 13;
unsigned long previousMillis = 0;
const long interval = 1000;

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis > interval) {
    previousMillis = currentMillis;
    digitalWrite(ledPin, !digitalRead(ledPin));
  }
}

medium

A. The code will cause a runtime error due to digitalWrite logic.

B. Using > instead of >= in the if condition causes timing issues.

C. The variable previousMillis should be int, not unsigned long.

D. digitalRead() cannot be used on output pins.

Solution

1. Step 1: Check use of digitalRead on output pin

   digitalRead() on an output pin is unreliable and not recommended for toggling.

2. Step 2: Understand proper toggle method

   Better to track LED state in a variable rather than reading output pin state.

3. Final Answer:

   digitalRead() cannot be used on output pins. -> Option D

4. Quick Check:

   Don't use digitalRead on output pins [OK]

Hint: Avoid digitalRead on pins set as OUTPUT [OK]

Common Mistakes:

• Thinking > vs >= causes major error
• Believing previousMillis type is wrong
• Assuming digitalWrite logic causes runtime error

5. You want to blink two LEDs independently using the Blink without delay pattern: LED1 every 500 ms and LED2 every 1000 ms. Which approach correctly manages both LEDs without blocking the program?

hard

A. Toggle LED1 every 500 ms and LED2 every 1000 ms using nested for loops.

B. Use one previousMillis variable and toggle both LEDs at the same time every 500 ms.

C. Use two separate previousMillis variables and check each interval independently in loop().

D. Use delay(500) for LED1 and delay(1000) for LED2 in sequence inside loop().

Solution

1. Step 1: Understand independent timing needs

   Each LED needs its own timer variable to track its blinking interval separately.

2. Step 2: Avoid blocking delays and incorrect loops

   Using delay() or nested loops blocks code and prevents independent blinking.

3. Final Answer:

   Use two separate previousMillis variables and check each interval independently in loop(). -> Option C

4. Quick Check:

   Separate timers for independent blinking [OK]

Hint: Track each LED's time separately with its own variable [OK]

Common Mistakes:

• Using one timer for both LEDs
• Using delay() which blocks code
• Trying nested loops for timing