Custom characters on LCD in Arduino - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What does this Arduino LCD code output?

Consider this Arduino code snippet that creates a custom character and displays it on an LCD:

byte smiley[8] = {
  0b00000,
  0b01010,
  0b01010,
  0b00000,
  0b10001,
  0b01110,
  0b00000,
  0b00000
};

void setup() {
  lcd.begin(16, 2);
  lcd.createChar(0, smiley);
  lcd.setCursor(0, 0);
  lcd.write(byte(0));
}

void loop() {}

What will appear on the LCD screen?

Arduino

byte smiley[8] = {
  0b00000,
  0b01010,
  0b01010,
  0b00000,
  0b10001,
  0b01110,
  0b00000,
  0b00000
};

void setup() {
  lcd.begin(16, 2);
  lcd.createChar(0, smiley);
  lcd.setCursor(0, 0);
  lcd.write(byte(0));
}

void loop() {}

A Compilation error due to incorrect byte array size

B The LCD shows a blank space at the first position

C The LCD displays a random character at the first position

D A smiling face icon appears at the first position on the LCD

💡 Hint

Custom characters are stored in CGRAM and displayed by writing their index as a byte.

The createChar function stores the custom pattern in CGRAM slot 0. Writing byte(0) prints that custom character, which looks like a smiling face.

🧠 Conceptual

intermediate

How many custom characters can an Arduino LCD typically store?

When using the LiquidCrystal library on a standard 16x2 LCD, how many custom characters can you create and store at the same time?

A 8 custom characters

B 16 custom characters

C 4 custom characters

D 32 custom characters

💡 Hint

Think about the CGRAM memory size in HD44780 compatible LCDs.

Standard HD44780 LCD controllers have 64 bytes of CGRAM, enough for 8 characters of 8 bytes each.

🔧 Debug

advanced

Why does this custom character not display correctly?

Look at this Arduino code snippet:

byte heart[7] = {
  0b00000,
  0b01010,
  0b11111,
  0b11111,
  0b11111,
  0b01110,
  0b00100
};

void setup() {
  lcd.begin(16, 2);
  lcd.createChar(1, heart);
  lcd.setCursor(0, 0);
  lcd.write(byte(1));
}

void loop() {}

The heart shape does not appear as expected on the LCD. What is the most likely cause?

A The LCD is not initialized with <code>lcd.begin</code>

B The <code>lcd.write</code> function cannot print custom characters

C The byte array has only 7 rows instead of 8, causing incorrect display

D The <code>createChar</code> index 1 is invalid; it must be 0

💡 Hint

Custom characters require exactly 8 bytes for 8 rows.

The custom character array must have 8 bytes, one for each row. Missing one row causes the LCD to display garbage or nothing.

📝 Syntax

advanced

Which option correctly defines a custom character array for LCD?

Choose the correct syntax to define a custom character pattern for an Arduino LCD:

A byte customChar[8] = {0b00000, 0b01010, 0b10101, 0b01010, 0b00000, 0b00000, 0b00000, 0b00000};

B byte customChar[8] = (0b00000, 0b01010, 0b10101, 0b01010, 0b00000, 0b00000, 0b00000, 0b00000);

C byte customChar[7] = {0b00000, 0b01010, 0b10101, 0b01010, 0b00000, 0b00000, 0b00000};

D byte customChar = {0b00000, 0b01010, 0b10101, 0b01010, 0b00000, 0b00000, 0b00000, 0b00000};

💡 Hint

Remember how to declare arrays in Arduino (C++).

Option A correctly declares an array of 8 bytes with curly braces. Option A misses the array size, C has only 7 elements, and D uses parentheses instead of braces.

🚀 Application

expert

How to display multiple custom characters on LCD simultaneously?

You want to display two different custom characters side by side on a 16x2 LCD using Arduino. You have created two custom characters at indexes 0 and 1. Which code snippet correctly displays both characters on the first row?

A lcd.setCursor(0, 0); lcd.write(0); lcd.write(1);

B lcd.setCursor(0, 0); lcd.write(byte(0)); lcd.write(byte(1));

C lcd.setCursor(0, 0); lcd.print(byte(0)); lcd.print(byte(1));

D lcd.setCursor(0, 0); lcd.print(0); lcd.print(1);

💡 Hint

Use write to print custom characters by their byte index.

The lcd.write(byte(n)) function prints the custom character stored at index n. Using print with byte values prints their ASCII codes, not custom characters.