Writing HIGH and LOW to output pins in Embedded C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set pin 5 to HIGH.

Embedded C

digitalWrite(5, [1]);

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

AHIGH

BLOW

CINPUT

DOUTPUT

Attempts:

3 left

💡 Hint

Common Mistakes

Using LOW instead of HIGH will turn the pin off.

Using INPUT or OUTPUT in digitalWrite is incorrect.

To set a pin to HIGH, use the constant HIGH in the digitalWrite function.

2fill in blank

medium

Complete the code to set pin 3 to LOW.

Embedded C

digitalWrite(3, [1]);

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

AOUTPUT

BLOW

CINPUT

DHIGH

Attempts:

3 left

💡 Hint

Common Mistakes

Using HIGH will turn the pin on instead of off.

Using INPUT or OUTPUT is wrong in digitalWrite.

To turn off the pin, use LOW in digitalWrite.

3fill in blank

hard

Fix the error in setting pin 7 to HIGH.

Embedded C

digitalWrite([1], HIGH);

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

ALOW

BHIGH

COUTPUT

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 of digitalWrite must be the pin number, here 7.

4fill in blank

hard

Fill both blanks to set pin 9 as output and then write HIGH to it.

Embedded C

pinMode([1], [2]);
digitalWrite(9, HIGH);

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

A9

BLOW

COUTPUT

DINPUT

Attempts:

3 left

💡 Hint

Common Mistakes

Using LOW or INPUT in pinMode instead of OUTPUT.

Using wrong pin number.

Use pinMode(9, OUTPUT); to set pin 9 as output before writing HIGH.

5fill in blank

hard

Fill all three blanks to set pin 4 as output, write LOW, then write HIGH.

Embedded C

pinMode([1], [2]);
digitalWrite(4, [3]);
digitalWrite(4, HIGH);

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

A4

BOUTPUT

CLOW

DINPUT

Attempts:

3 left

💡 Hint

Common Mistakes

Using INPUT instead of OUTPUT in pinMode.

Writing HIGH instead of LOW in the second digitalWrite.

First set pin 4 as output with pinMode(4, OUTPUT);, then write LOW to turn it off, then HIGH to turn it on.

Practice

1. Which function is used to set a pin as an output before writing HIGH or LOW to it?

easy

A. setPinMode(pin, HIGH)

B. digitalWrite(pin, OUTPUT)

C. pinMode(pin, OUTPUT)

D. writePin(pin, OUTPUT)

Solution

1. Step 1: Understand pin configuration

   Before writing HIGH or LOW, the pin must be set as an output to control voltage.

2. Step 2: Identify the correct function

   The function to set pin mode is pinMode(pin, OUTPUT), which configures the pin for output.

3. Final Answer:

   pinMode(pin, OUTPUT) -> Option C

4. Quick Check:

   Set pin as output = pinMode(pin, OUTPUT) [OK]

Hint: Set pin mode with pinMode before writing HIGH or LOW [OK]

Common Mistakes:

• Using digitalWrite to set pin mode
• Confusing HIGH/LOW with OUTPUT/INPUT
• Forgetting to set pin mode before writing

2. Which of the following is the correct syntax to turn pin 5 ON (HIGH) in embedded C?

easy

A. digitalWrite(5, 1);

B. digitalWrite(5, ON);

C. digitalWrite(5, OUTPUT);

D. digitalWrite(5, HIGH);

Solution

1. Step 1: Identify the function to write pin state

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

2. Step 2: Use correct constants

   Use HIGH to turn the pin ON. The correct syntax is digitalWrite(5, HIGH);.

3. Final Answer:

   digitalWrite(5, HIGH); -> Option D

4. Quick Check:

   Turn pin ON = digitalWrite(pin, HIGH) [OK]

Hint: Use HIGH constant, not ON or numbers, for clarity [OK]

Common Mistakes:

• Using ON instead of HIGH
• Using OUTPUT instead of HIGH
• Using numeric 1 instead of HIGH constant

3. What will be the output state of pin 3 after running this code?

pinMode(3, OUTPUT);
digitalWrite(3, LOW);
digitalWrite(3, HIGH);

medium

A. Pin 3 will be LOW

B. Pin 3 will be HIGH

C. Pin 3 will be in input mode

D. Pin 3 will be undefined

Solution

1. Step 1: Set pin 3 as output

   The code sets pin 3 as output with pinMode(3, OUTPUT);.

2. Step 2: Write LOW then HIGH to pin 3

   First, pin 3 is set LOW, then immediately set HIGH, so final state is HIGH.

3. Final Answer:

   Pin 3 will be HIGH -> Option B

4. Quick Check:

   Last digitalWrite sets pin state = HIGH [OK]

Hint: Last digitalWrite sets the pin state [OK]

Common Mistakes:

• Assuming pin stays LOW after writing HIGH
• Forgetting pinMode sets output mode
• Thinking pin state is undefined without delay

4. Identify the error in this code snippet:

pinMode(7, OUTPUT);
digitalWrite(7, HIGH)
digitalWrite(7, LOW);

medium

A. Missing semicolon after digitalWrite(7, HIGH)

B. pinMode should be called after digitalWrite

C. HIGH and LOW are not valid constants

D. Pin number 7 cannot be used

Solution

1. Step 1: Check syntax line by line

   The second line digitalWrite(7, HIGH) is missing a semicolon at the end.

2. Step 2: Confirm other lines are correct

   pinMode(7, OUTPUT); and digitalWrite(7, LOW); are correct syntax.

3. Final Answer:

   Missing semicolon after digitalWrite(7, HIGH) -> Option A

4. Quick Check:

   Every statement must end with semicolon [OK]

Hint: Check each line ends with a semicolon [OK]

Common Mistakes:

• Forgetting semicolon after function calls
• Calling pinMode after digitalWrite
• Misusing HIGH/LOW constants

5. You want to toggle pin 10 ON and OFF every second in a loop. Which code snippet correctly sets pin 10 HIGH then LOW with a 1-second delay between states?

hard

A. pinMode(10, OUTPUT);
digitalWrite(10, HIGH);
delay(1000);
digitalWrite(10, LOW);
delay(1000);

B. digitalWrite(10, HIGH);
delay(1000);
digitalWrite(10, LOW);
delay(1000);

C. pinMode(10, INPUT);
digitalWrite(10, HIGH);
delay(1000);

D. pinMode(10, OUTPUT);
digitalWrite(10, LOW);
digitalWrite(10, HIGH);

Solution

1. Step 1: Set pin 10 as output

   Use pinMode(10, OUTPUT); to configure pin 10 for output.

2. Step 2: Write HIGH, wait, then LOW, wait

   Use digitalWrite(10, HIGH); then delay(1000); to wait 1 second, then digitalWrite(10, LOW); and delay again.

3. Final Answer:

   pinMode(10, OUTPUT); digitalWrite(10, HIGH); delay(1000); digitalWrite(10, LOW); delay(1000); -> Option A

4. Quick Check:

   Set output, write states with delay between [OK]

Hint: Always set pinMode before toggling with delays [OK]

Common Mistakes:

• Forgetting to set pinMode as OUTPUT
• Missing delay between HIGH and LOW
• Setting pinMode to INPUT instead of OUTPUT