LED control patterns in Embedded C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to turn on the LED connected to pin 13.

Embedded C

digitalWrite([1], HIGH);

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

A13

B12

C10

D9

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong pin number.

Confusing HIGH and LOW values.

The LED is connected to pin 13, so we use digitalWrite(13, HIGH); to turn it on.

2fill in blank

medium

Complete the code to make the LED blink by turning it off.

Embedded C

digitalWrite(13, [1]);

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

AHIGH

BLOW

CON

DOFF

Attempts:

3 left

💡 Hint

Common Mistakes

Using HIGH instead of LOW to turn off the LED.

Using undefined constants like ON or OFF.

To turn the LED off, we use LOW with digitalWrite.

3fill in blank

hard

Fix the error in the code to set pin 13 as output.

Embedded C

pinMode([1], OUTPUT);

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

A13

B11

C12

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Setting the wrong pin as output.

Confusing input and output modes.

Pin 13 is the correct pin connected to the LED and must be set as output.

4fill in blank

hard

Fill both blanks to create a pattern that turns the LED on and off with a delay.

Embedded C

digitalWrite(13, [1]);
delay([2]);

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

AHIGH

BLOW

C1000

D500

Attempts:

3 left

💡 Hint

Common Mistakes

Using LOW to turn the LED on.

Using too short or too long delay values.

Use HIGH to turn the LED on and 1000 milliseconds delay for 1 second.

5fill in blank

hard

Fill all three blanks to complete the loop that blinks the LED on and off with delays.

Embedded C

void loop() {
  digitalWrite(13, [1]);
  delay([2]);
  digitalWrite(13, [3]);
  delay([4]);
}

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

AHIGH

B500

CLOW

D1000

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping HIGH and LOW values.

Forgetting the delay between states.

The LED is turned on with HIGH, then delayed 500 ms, then turned off with LOW, then delayed 500 ms again.

Practice

1. What is the main purpose of using LED control patterns in embedded C programming?

easy

A. To create visual effects by turning LEDs on and off in specific sequences

B. To increase the processing speed of the microcontroller

C. To store data in the microcontroller's memory

D. To connect the microcontroller to the internet

Solution

1. Step 1: Understand LED control patterns

   LED control patterns are used to create visual effects by controlling LEDs.

2. Step 2: Identify the purpose in embedded systems

   They help show device status or create decorative light sequences by turning LEDs on and off.

3. Final Answer:

   To create visual effects by turning LEDs on and off in specific sequences -> Option A

4. Quick Check:

   LED patterns = visual effects [OK]

Hint: LED patterns control lights, not speed or memory [OK]

Common Mistakes:

• Confusing LED patterns with data storage
• Thinking LED patterns improve processing speed
• Assuming LED patterns connect to the internet

2. Which of the following is the correct syntax to turn on an LED connected to pin 5 using embedded C?

easy

A. digitalWrite(HIGH, 5);

B. digitalWrite(5, ON);

C. digitalWrite(5, HIGH);

D. digitalWrite(ON, 5);

Solution

1. Step 1: Recall digitalWrite syntax

   The function digitalWrite(pin, value) sets the pin to HIGH or LOW.

2. Step 2: Match correct parameters

   Pin number comes first, then the value HIGH to turn LED on.

3. Final Answer:

   digitalWrite(5, HIGH); -> Option C

4. Quick Check:

   digitalWrite(pin, HIGH) = turn LED on [OK]

Hint: Pin number first, then HIGH or LOW [OK]

Common Mistakes:

• Swapping pin and value order
• Using ON instead of HIGH
• Using lowercase for HIGH

3. What will be the output on the LED connected to pin 3 after running this code snippet?

for(int i = 0; i < 3; i++) {
  digitalWrite(3, HIGH);
  delay(500);
  digitalWrite(3, LOW);
  delay(500);
}

medium

A. LED stays OFF continuously

B. LED stays ON continuously for 1.5 seconds

C. LED blinks once and stays OFF

D. LED blinks 3 times with 0.5 second ON and 0.5 second OFF

Solution

1. Step 1: Analyze the loop iterations

   The loop runs 3 times, each time turning LED ON then OFF with delays.

2. Step 2: Understand delay timing

   Each ON and OFF lasts 500ms, so LED blinks 3 times with equal ON/OFF intervals.

3. Final Answer:

   LED blinks 3 times with 0.5 second ON and 0.5 second OFF -> Option D

4. Quick Check:

   Loop 3 times with delay = 3 blinks [OK]

Hint: Count loop runs and delays for blink count [OK]

Common Mistakes:

• Ignoring the loop count
• Confusing delay units
• Assuming LED stays ON

4. Identify the error in this LED blinking code:

void loop() {
  digitalWrite(2, HIGH);
  delay(1000);
  digitalWrite(2, HIGH);
  delay(1000);
}

medium

A. delay() function is used incorrectly

B. LED never turns OFF because digitalWrite(2, HIGH) is used twice

C. Pin 2 is not set as OUTPUT

D. digitalWrite() syntax is wrong

Solution

1. Step 1: Check LED ON/OFF commands

   Both digitalWrite calls set pin 2 to HIGH, so LED stays ON.

2. Step 2: Identify missing OFF command

   LED never turns OFF because digitalWrite(2, LOW) is missing.

3. Final Answer:

   LED never turns OFF because digitalWrite(2, HIGH) is used twice -> Option B

4. Quick Check:

   Same HIGH twice = no OFF [OK]

Hint: LED needs HIGH then LOW to blink [OK]

Common Mistakes:

• Assuming delay is wrong
• Forgetting to set pin mode
• Thinking syntax is incorrect

5. You want to create a running LED pattern on 4 LEDs connected to pins 2, 3, 4, and 5. Which code snippet correctly implements this pattern?

hard

A. for(int i = 2; i <= 5; i++) {
digitalWrite(i, HIGH);
delay(200);
digitalWrite(i, LOW);
}

B. for(int i = 2; i <= 5; i++) {
digitalWrite(i, LOW);
delay(200);
digitalWrite(i, HIGH);
}

C. digitalWrite(2, HIGH);
digitalWrite(3, HIGH);
digitalWrite(4, HIGH);
digitalWrite(5, HIGH);
delay(200);
digitalWrite(2, LOW);
digitalWrite(3, LOW);
digitalWrite(4, LOW);
digitalWrite(5, LOW);

D. for(int i = 5; i >= 2; i--) {
digitalWrite(i, HIGH);
delay(200);
}

Solution

1. Step 1: Understand running LED pattern

   Running LED means turning ON one LED at a time in sequence, then OFF before next.

2. Step 2: Analyze each option

   for(int i = 2; i <= 5; i++) { digitalWrite(i, HIGH); delay(200); digitalWrite(i, LOW); } loops from pin 2 to 5, turns each LED ON, delays, then OFF, creating running effect.

3. Final Answer:

   for(int i = 2; i <= 5; i++) { digitalWrite(i, HIGH); delay(200); digitalWrite(i, LOW); } -> Option A

4. Quick Check:

   Loop ON then OFF per LED = running pattern [OK]

Hint: Turn ON then OFF each LED in order [OK]

Common Mistakes:

• Turning all LEDs ON at once
• Not turning off the LED after delay
• Turning LEDs OFF before ON