Custom characters on LCD in Arduino

Introduction

Sometimes the built-in characters on an LCD are not enough. Custom characters let you show your own shapes or symbols.

You want to display a smiley face or a heart on the LCD.

You need special icons like arrows or battery levels.

You want to create a small game or animation on the LCD.

You want to show letters or symbols not included in the LCD's default set.

Syntax

Arduino

byte customChar[8] = {
  B00000,
  B01010,
  B10101,
  B10001,
  B10101,
  B01010,
  B00000,
  B00000
};

lcd.createChar(location, customChar);
lcd.write(byte(location));

byte customChar[8] holds 8 rows of 5 pixels each (bits 0-4 used).

location is a number from 0 to 7 to store the custom character.

Examples

This creates a smiley face and shows it on the LCD at position 0.

Arduino

byte smiley[8] = {
  B00000,
  B01010,
  B00000,
  B00000,
  B10001,
  B01110,
  B00000,
  B00000
};
lcd.createChar(0, smiley);
lcd.write(byte(0));

This creates a heart shape and displays it using location 1.

Arduino

byte heart[8] = {
  B00000,
  B01010,
  B11111,
  B11111,
  B11111,
  B01110,
  B00100,
  B00000
};
lcd.createChar(1, heart);
lcd.write(byte(1));

Sample Program

This program shows the word "Hello" followed by a smiley face on the LCD.

Arduino

#include <LiquidCrystal.h>

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

byte smiley[8] = {
  B00000,
  B01010,
  B00000,
  B00000,
  B10001,
  B01110,
  B00000,
  B00000
};

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

void loop() {
  // Nothing here
}

Important Notes

You can only store up to 8 custom characters at a time (locations 0-7).

Each character is 5 pixels wide and 8 pixels tall.

Use lcd.write(byte(location)) to display your custom character.

Summary

Custom characters let you add your own symbols to the LCD.

Define 8 rows of pixels using bytes with bits 0-4 for each row.

Store and show them using createChar and write.

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()