digitalWrite() for output control in Arduino - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set pin 13 to HIGH.

Arduino

digitalWrite(13, [1]);

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

AHIGH

BOUTPUT

CLOW

DINPUT

Attempts:

3 left

💡 Hint

Common Mistakes

Using LOW instead of HIGH turns the pin off.

Using INPUT or OUTPUT in digitalWrite() is incorrect.

digitalWrite() sets the voltage of the pin. HIGH means 5V (on).

2fill in blank

medium

Complete the code to turn off the LED connected to pin 9.

Arduino

digitalWrite(9, [1]);

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

ALOW

BHIGH

CINPUT

DOUTPUT

Attempts:

3 left

💡 Hint

Common Mistakes

Using HIGH will keep the LED on.

INPUT and OUTPUT are not valid values for digitalWrite().

LOW sets the pin voltage to 0V, turning the LED off.

3fill in blank

hard

Fix the error in the code to set pin 7 HIGH.

Arduino

digitalWrite([1], HIGH);

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

AOUTPUT

BHIGH

CLOW

D7

Attempts:

3 left

💡 Hint

Common Mistakes

Putting HIGH as the pin number causes errors.

Using OUTPUT or LOW as pin number is incorrect.

The first argument must be the pin number, here 7.

4fill in blank

hard

Fill both blanks to turn pin 5 off and pin 6 on.

Arduino

digitalWrite([1], LOW);
digitalWrite([2], HIGH);

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

A5

B6

CHIGH

DLOW

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping pin numbers or voltage values.

Using HIGH where LOW is needed.

Pin 5 is set to LOW to turn off, pin 6 to HIGH to turn on.

5fill in blank

hard

Fill all three blanks to set pin 3 HIGH, pin 4 LOW, and pin 8 HIGH.

Arduino

digitalWrite([1], HIGH);
digitalWrite([2], LOW);
digitalWrite([3], HIGH);

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

A3

B4

C8

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up pin numbers or voltage states.

Using pin 5 which is not in the task.

Pin 3 and 8 are set HIGH to turn on, pin 4 LOW to turn off.

Practice

1. What does the digitalWrite() function do in Arduino programming?

easy

A. It sets the analog value of a pin.

B. It reads the voltage from a digital pin.

C. It initializes the serial communication.

D. It sets a digital pin to HIGH or LOW voltage.

Solution

1. Step 1: Understand the purpose of digitalWrite()

   The function digitalWrite() is used to control the voltage level on a digital pin, setting it either HIGH (on) or LOW (off). It does not read values (that's digitalRead()), nor does it set analog values or initialize serial communication.

2. Final Answer:

   It sets a digital pin to HIGH or LOW voltage. -> Option D

3. Quick Check:

   digitalWrite() controls pin voltage = D [OK]

Hint: digitalWrite sets pin ON or OFF voltage [OK]

Common Mistakes:

• Confusing digitalWrite() with digitalRead()
• Thinking digitalWrite() reads pin values
• Mixing digitalWrite() with analogWrite()

2. Which of the following is the correct syntax to turn on an LED connected to pin 13 using digitalWrite()?

easy

A. digitalWrite(13, HIGH);

B. digitalWrite(13, LOW);

C. digitalWrite(13, ON);

D. digitalWrite(13, TRUE);

Solution

1. Step 1: Recall correct constants and check options

   digitalWrite() uses HIGH and LOW constants. To turn on, use HIGH. A uses ON (not valid), B uses LOW (turns off), D uses TRUE (not valid). Only C: digitalWrite(13, HIGH); is correct.

2. Final Answer:

   digitalWrite(13, HIGH); -> Option A

3. Quick Check:

   Use HIGH or LOW with digitalWrite() = C [OK]

Hint: Use HIGH or LOW, not ON or TRUE [OK]

Common Mistakes:

• Using ON or TRUE instead of HIGH
• Using LOW instead of HIGH
• Forgetting to set pinMode to OUTPUT first

3. What will be the output on pin 8 after running this code snippet?

pinMode(8, OUTPUT);
digitalWrite(8, LOW);
digitalWrite(8, HIGH);
digitalWrite(8, LOW);

medium

A. Pin 8 will toggle rapidly.

B. Pin 8 will be HIGH (on).

C. Pin 8 will be LOW (off).

D. Pin 8 will cause a syntax error.

Solution

1. Step 1: Trace the digitalWrite() calls

   pinMode sets OUTPUT, then LOW, HIGH, LOW. Final LOW so pin off.

2. Final Answer:

   Pin 8 will be LOW (off). -> Option C

3. Quick Check:

   Last digitalWrite sets pin LOW = A [OK]

Hint: Last digitalWrite() sets pin state [OK]

Common Mistakes:

• Assuming pin toggles automatically
• Confusing initial and final pin states
• Thinking multiple digitalWrite calls cause errors

4. Identify the error in this Arduino code snippet:

digitalWrite(12, HIGH);
pinMode(12, OUTPUT);

medium

A. No error, code runs fine.

B. pinMode() must be called before digitalWrite().

C. digitalWrite() cannot use pin 12.

D. HIGH is not a valid value for digitalWrite().

Solution

1. Step 1: Check order of pinMode() and digitalWrite()

   pinMode() must set OUTPUT before digitalWrite(), otherwise unexpected behavior. Here digitalWrite first.

2. Final Answer:

   pinMode() must be called before digitalWrite(). -> Option B

3. Quick Check:

   Set pinMode before digitalWrite = A [OK]

Hint: Always set pinMode(OUTPUT) before digitalWrite() [OK]

Common Mistakes:

• Calling digitalWrite before pinMode
• Assuming pinMode defaults to OUTPUT
• Using invalid pin numbers

5. You want to blink an LED connected to pin 9 on and off every second. Which code snippet correctly uses digitalWrite() inside the loop() function to achieve this?

hard

A. digitalWrite(9, HIGH);
delay(1000);
digitalWrite(9, LOW);
delay(1000);

B. digitalWrite(9, HIGH);
digitalWrite(9, LOW);
delay(1000);

C. pinMode(9, OUTPUT);
digitalWrite(9, HIGH);
delay(1000);

D. digitalWrite(9, HIGH);
delay(500);
digitalWrite(9, HIGH);
delay(500);

Solution

1. Step 1: Understand blinking and analyze options

   Blink: HIGH, delay(1000), LOW, delay(1000). A: HIGH immediate LOW, no on time. C: pinMode in loop inefficient, no LOW. D: HIGH twice, always on. Only B correct.

2. Final Answer:

   digitalWrite(9, HIGH); delay(1000); digitalWrite(9, LOW); delay(1000); -> Option A

3. Quick Check:

   Turn ON, delay, turn OFF, delay = B [OK]

Hint: Turn ON, delay, turn OFF, delay for blinking [OK]

Common Mistakes:

• Missing delay between ON and OFF
• Not turning LED OFF after ON
• Setting pinMode inside loop repeatedly