16x2 LCD with LiquidCrystal library in Arduino - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output on the LCD?

Consider this Arduino code using the LiquidCrystal library to display text on a 16x2 LCD. What will appear on the LCD screen after running this code?

Arduino

#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() {
  lcd.begin(16, 2);
  lcd.print("Hello, World!");
  lcd.setCursor(0, 1);
  lcd.print("LCD Test");
}

void loop() {}

A First line: (empty)\nSecond line: Hello, World! LCD Test

B First line: LCD Test\nSecond line: Hello, World!

C First line: Hello, World! LCD Test\nSecond line: (empty)

D First line: Hello, World!\nSecond line: LCD Test

💡 Hint

Remember that lcd.setCursor(col, row) sets the position for the next print.

The lcd.print("Hello, World!") prints on the first line starting at column 0. Then lcd.setCursor(0, 1) moves the cursor to the start of the second line, where lcd.print("LCD Test") prints the second line.

🧠 Conceptual

intermediate

What does lcd.begin(16, 2) do?

In the LiquidCrystal library, what is the purpose of the lcd.begin(16, 2) command?

A It initializes the LCD with 16 columns and 2 rows, setting up the display size.

B It clears the LCD screen and turns off the backlight.

C It sets the cursor to the first column and first row.

D It loads a custom character set into the LCD memory.

💡 Hint

Think about what parameters begin() takes and what the LCD needs before printing.

The lcd.begin(16, 2) command tells the library the LCD size is 16 columns wide and 2 rows tall. This prepares the LCD to display text correctly.

🔧 Debug

advanced

Why does this code not display anything?

Look at this Arduino code snippet. Why does the LCD remain blank after uploading?

Arduino

#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() {
  lcd.print("Hello");
  lcd.begin(16, 2);
}

void loop() {}

A Because <code>lcd.begin()</code> must be called before any <code>lcd.print()</code> calls to initialize the display.

B Because the <code>loop()</code> function is empty and must contain <code>lcd.display()</code>.

C Because the pins are incorrectly assigned and need to be changed.

D Because the LCD backlight is off and must be turned on manually.

💡 Hint

Think about the order of initialization and printing.

The lcd.begin() function must be called before printing anything. It sets up the LCD hardware. Calling lcd.print() before lcd.begin() does nothing because the LCD is not ready.

📝 Syntax

advanced

Which code snippet correctly sets the cursor and prints on second line?

Which of the following code snippets correctly moves the cursor to the start of the second line and prints "Ready" on a 16x2 LCD?

A

lcd.setCursor(0, 2);
lcd.print("Ready");

B

lcd.setCursor(1, 0);
lcd.print("Ready");

C

lcd.setCursor(0, 1);
lcd.print("Ready");

D

lcd.setCursor(1, 1);
lcd.print("Ready");

💡 Hint

Remember that row numbering starts at 0.

Row 0 is the first line, row 1 is the second line. Column numbering also starts at 0. So lcd.setCursor(0, 1) moves to the first column of the second line.

🚀 Application

expert

How many characters fit on a 16x2 LCD and what happens if you print more?

You have a 16x2 LCD connected and initialized with lcd.begin(16, 2). How many characters can you display at once? What happens if you print a string longer than that?

A You can display 32 characters total. Printing more characters will overwrite the first line repeatedly.

B You can display 32 characters total. Printing more characters continues printing off-screen and they are lost (not visible).

C You can display 16 characters total. Printing more characters causes the LCD to reset.

D You can display 32 characters total (16 per line). Printing more scrolls the text horizontally on the first line only.

💡 Hint

Think about how the LCD handles text longer than its display size.

A 16x2 LCD can show 16 characters on each of its 2 lines, totaling 32 visible characters. If you print more than 32 characters, the extra characters are sent to the LCD memory but are not visible because the display does not scroll automatically. They are effectively lost unless you manually scroll or reposition the cursor.

Practice

1. What does the lcd.begin(16, 2) command do in the LiquidCrystal library?

easy

A. It clears the LCD screen.

B. It sets up the LCD screen size to 16 columns and 2 rows.

C. It moves the cursor to the first position.

D. It prints text on the LCD screen.

Solution

1. Step 1: Understand lcd.begin() function

   The lcd.begin() function initializes the LCD with the number of columns and rows.

2. Step 2: Apply to given parameters

   Using lcd.begin(16, 2) sets the screen size to 16 columns and 2 rows.

3. Final Answer:

   It sets up the LCD screen size to 16 columns and 2 rows. -> Option B

4. Quick Check:

   lcd.begin(16, 2) = sets screen size [OK]

Hint: Remember lcd.begin sets screen size first [OK]

Common Mistakes:

• Thinking lcd.begin clears the screen
• Confusing lcd.begin with lcd.print
• Assuming lcd.begin moves the cursor

2. Which of the following is the correct way to create a LiquidCrystal object for pins 12, 11, 5, 4, 3, 2?

easy

A. LiquidCrystal lcd = (12, 11, 5, 4, 3, 2);

B. LiquidCrystal lcd(2, 3, 4, 5, 11, 12);

C. LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

D. LiquidCrystal lcd(12, 11, 5, 4);

Solution

1. Step 1: Recall LiquidCrystal constructor syntax

   The constructor requires 6 pins: RS, Enable, D4, D5, D6, D7 in order.

2. Step 2: Match given pins to correct syntax

   LiquidCrystal lcd(12, 11, 5, 4, 3, 2); matches the correct order and number of pins.

3. Final Answer:

   LiquidCrystal lcd(12, 11, 5, 4, 3, 2); -> Option C

4. Quick Check:

   Constructor needs 6 pins in order [OK]

Hint: Count pins: constructor needs exactly 6 pins [OK]

Common Mistakes:

• Using wrong number of pins
• Wrong pin order
• Using assignment instead of constructor

3. What will be displayed on the LCD after running this code?

lcd.begin(16, 2);
lcd.setCursor(0, 1);
lcd.print("Hello");

medium

A. Hello on the second row

B. Nothing is displayed

C. Hello on both rows

D. Hello on the first row

Solution

1. Step 1: Understand lcd.setCursor(0, 1)

   Cursor moves to column 0, row 1 (second row, since rows start at 0).

2. Step 2: lcd.print("Hello") prints at cursor

   Text "Hello" appears on the second row starting at first column.

3. Final Answer:

   Hello on the second row -> Option A

4. Quick Check:

   setCursor(0,1) = second row [OK]

Hint: Rows start at 0, so row 1 is second row [OK]

Common Mistakes:

• Assuming row 1 is first row
• Forgetting cursor position before print
• Expecting text on both rows

4. Identify the error in this code snippet:

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
lcd.begin(16, 2);
lcd.setCursor(1, 2);
lcd.print("Hi");

medium

A. Cursor row 2 is invalid for 2-row LCD

B. lcd.begin() is missing

C. lcd.print() syntax is wrong

D. LiquidCrystal object not created properly

Solution

1. Step 1: Check lcd.setCursor parameters

   Rows are 0 and 1 for a 2-row LCD; row 2 is out of range.

2. Step 2: Confirm other code parts

   lcd.begin() is present, object created correctly, and print syntax is correct.

3. Final Answer:

   Cursor row 2 is invalid for 2-row LCD -> Option A

4. Quick Check:

   Row index must be 0 or 1 for 16x2 LCD [OK]

Hint: Rows start at 0; max row for 2-row LCD is 1 [OK]

Common Mistakes:

• Using row 2 instead of 0 or 1
• Forgetting lcd.begin() call
• Incorrect object creation syntax

5. You want to display the word "Ready" centered on the first row of a 16x2 LCD. Which code snippet correctly sets the cursor before printing?

hard

A. lcd.setCursor(8, 0); lcd.print("Ready");

B. lcd.setCursor(5, 0); lcd.print("Ready");

C. lcd.setCursor(7, 0); lcd.print("Ready");

D. lcd.setCursor(6, 0); lcd.print("Ready");

Solution

1. Step 1: Calculate starting position for centering

   LCD width is 16 columns; word length is 5 letters. (16 - 5) / 2 = 5.5, round to 6.

2. Step 2: Set cursor to column 6 on first row (row 0)

   Use lcd.setCursor(6, 0) to start printing "Ready" centered.

3. Final Answer:

   lcd.setCursor(6, 0); lcd.print("Ready"); -> Option D

4. Quick Check:

   (16-5)/2 = 5.5 ≈ 6 for centering [OK]

Hint: Center = (screen width - text length) / 2 rounded [OK]

Common Mistakes:

• Using wrong column for centering
• Confusing row numbers
• Not rounding the position