Custom characters on LCD in Arduino - Mini Project: Build & Apply

Custom characters on LCD

📖 Scenario: You have a small LCD screen connected to an Arduino. You want to show special smiley faces and symbols that are not in the default LCD set.

🎯 Goal: Create custom characters on the LCD and display them on the screen.

📋 What You'll Learn

Create a byte array for a custom character

Use the LCD library to create the custom character

Display the custom character on the LCD screen

💡 Why This Matters

🌍 Real World

Custom characters let you show icons, symbols, or small images on simple LCD screens, making your device more user-friendly and visually appealing.

💼 Career

Embedded systems developers often create custom LCD characters to improve device interfaces in appliances, instruments, and gadgets.

1

Create the custom character byte array

Create a byte array called smiley with 8 bytes to define a smiley face pattern exactly as: 0b00000, 0b01010, 0b01010, 0b00000, 0b10001, 0b01110, 0b00000, 0b00000

Arduino

# Create the byte array 'smiley' for the custom character
# Your code here

Hint

Each byte represents one row of pixels in the 5x8 character grid. Use binary numbers starting with 0b.

2

Initialize the LCD and create the custom character

Add code to initialize the LCD with lcd.begin(16, 2); and create the custom character with lcd.createChar(0, smiley); inside the setup() function.

Arduino

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

#include 
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() {
  // Initialize LCD and create custom character
  // Your code here
}

void loop() {
}

Hint

Use lcd.begin(16, 2); to set up the LCD size and lcd.createChar(0, smiley); to load your custom character into slot 0.

3

Display the custom character on the LCD

In the loop() function, add code to set the cursor to column 0, row 0 with lcd.setCursor(0, 0); and print the custom character using lcd.write(byte(0));.

Arduino

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

Hint

Use lcd.setCursor(0, 0); to move the cursor and lcd.write(byte(0)); to show the custom character stored in slot 0.

4

Show the custom character on the LCD screen

Upload the full program and observe the LCD screen. The custom smiley face character should appear at the top-left corner of the LCD.

Arduino

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

#include 
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

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

void loop() {
  lcd.setCursor(0, 0);
  lcd.write(byte(0));
  // Observe the LCD screen
  // Your code here
}

Hint

Upload the code to your Arduino and check the LCD screen. You should see the smiley character at the top-left corner.

Practice

1. What is the main purpose of using createChar() in Arduino LCD programming?

easy

A. To clear the LCD screen

B. To define a custom character pattern for the LCD

C. To set the cursor position on the LCD

D. To print a string on the LCD

Solution

1. Step 1: Understand the function of createChar()

   This function is used to define a new character pattern by specifying pixel rows for the LCD.

2. Step 2: Compare with other LCD functions

   Functions like clearing the screen, setting cursor, or printing strings are different and not related to defining custom characters.

3. Final Answer:

   To define a custom character pattern for the LCD -> Option B

4. Quick Check:

   createChar() defines custom characters [OK]

Hint: Remember: createChar defines, write displays [OK]

Common Mistakes:

• Confusing createChar with print or clear functions
• Thinking createChar moves the cursor
• Assuming createChar prints text directly

2. Which of the following is the correct way to declare a custom character array for createChar()?

easy

A. byte smiley[8] = {0, 10, 0, 0, 17, 14, 0, 0};

B. int smiley[8] = {0, 10, 0, 0, 17, 14, 0, 0};

C. char smiley[5] = {0, 10, 0, 0, 17};

D. byte smiley[7] = {0, 10, 0, 0, 17, 14, 0};

Solution

1. Step 1: Check data type and array size

   Custom characters require 8 bytes (one for each row) and use the byte type for pixel data.

2. Step 2: Validate array length and type

   byte smiley[8] = {0, 10, 0, 0, 17, 14, 0, 0}; uses byte type and 8 elements, matching the LCD custom character format.

3. Final Answer:

   byte smiley[8] = {0, 10, 0, 0, 17, 14, 0, 0}; -> Option A

4. Quick Check:

   8 bytes array with byte type = correct declaration [OK]

Hint: Custom chars need 8 bytes, not int or fewer elements [OK]

Common Mistakes:

• Using int instead of byte
• Using fewer than 8 elements
• Using char type which is signed and may cause issues

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

byte heart[8] = {0,10,31,31,31,14,4,0};
lcd.createChar(0, heart);
lcd.setCursor(0,0);
lcd.write(byte(0));

medium

A. The LCD prints the number 0

B. The LCD shows a blank space

C. The code causes a compile error

D. A heart-shaped custom character appears at the top-left corner

Solution

1. Step 1: Understand createChar and write usage

   The code defines a heart pattern, stores it at position 0, then writes character 0 at cursor (0,0).

2. Step 2: Predict LCD output

   Writing byte(0) displays the custom character stored at position 0, which is the heart shape.

3. Final Answer:

   A heart-shaped custom character appears at the top-left corner -> Option D

4. Quick Check:

   createChar + write(byte(0)) = custom char display [OK]

Hint: write(byte(0)) prints custom char stored at 0 [OK]

Common Mistakes:

• Expecting numeric 0 to print
• Forgetting to use byte() cast in write()
• Assuming createChar prints automatically

4. Identify the error in this code snippet for displaying a custom character:

byte star[8] = {4,14,21,4,4,0,4,0};
lcd.createChar(1, star);
lcd.setCursor(0,0);
lcd.write(1);

medium

A. Missing byte cast in lcd.write(1)

B. Array size is incorrect

C. createChar index must be 0, not 1

D. setCursor parameters are invalid

Solution

1. Step 1: Check usage of lcd.write()

   When writing a custom character, the index must be cast to byte, so lcd.write(byte(1)) is correct.

2. Step 2: Verify other parts

   Array size is 8, createChar index 1 is valid (0-7), setCursor(0,0) is valid.

3. Final Answer:

   Missing byte cast in lcd.write(1) -> Option A

4. Quick Check:

   Use byte() cast in write() for custom chars [OK]

Hint: Always cast index with byte() in lcd.write() [OK]

Common Mistakes:

• Not casting index to byte in lcd.write()
• Thinking createChar index must be zero
• Assuming setCursor(0,0) is invalid

5. You want to display two different custom characters side by side on the LCD. Which sequence correctly creates and displays them?

hard

A. Define two byte arrays, use createChar(1, char1) and createChar(2, char2), then write(1) and write(2).

B. Define one byte array with 16 elements, use createChar(0, array), then write(0) twice.

C. Define two byte arrays, use createChar(0, char1) and createChar(1, char2), then write(byte(0)) and write(byte(1)) in order.

D. Use createChar(0, char1) twice, then write(0) and write(1).

Solution

1. Step 1: Understand createChar indexing

   Custom characters are stored in slots 0 to 7. To display two different chars, use two slots, e.g., 0 and 1.

2. Step 2: Display characters correctly

   Use write(byte(0)) and write(byte(1)) to print the two custom characters side by side.

3. Final Answer:

   Define two byte arrays, use createChar(0, char1) and createChar(1, char2), then write(byte(0)) and write(byte(1)) in order. -> Option C

4. Quick Check:

   Two createChar slots + write(byte(index)) = display two chars [OK]

Hint: Use slots 0 and 1, write with byte() cast [OK]

Common Mistakes:

• Trying to store both chars in one array
• Using invalid createChar indexes like 2 or higher without checking
• Not casting index to byte in write()