Custom characters on LCD in Arduino - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a custom character on an LCD?

A custom character is a user-defined symbol or shape that you create and store in the LCD's memory to display instead of the standard characters.

beginner

How many custom characters can you create on a typical 16x2 LCD?

You can create up to 8 custom characters because the LCD's memory allows storing 8 character patterns at a time.

beginner

What Arduino library is commonly used to control LCDs and create custom characters?

The LiquidCrystal library is commonly used to control LCDs and create custom characters with the createChar() function.

intermediate

Explain the purpose of the createChar() function in Arduino LCD programming.

The createChar() function stores a custom 5x8 pixel pattern in the LCD's memory at a specified location, allowing you to display that pattern as a character.

intermediate

How do you display a custom character after creating it on the LCD?

After creating a custom character with createChar(), you display it by writing its location number (0 to 7) to the LCD using the write() function.

How many pixels wide is each custom character on a typical 16x2 LCD?

A 2 pixels

B 8 pixels

C 16 pixels

D 5 pixels

Each custom character is 5 pixels wide and 8 pixels tall on a standard LCD.

Which Arduino function is used to create a custom character on an LCD?

A lcd.createChar()

B lcd.begin()

C lcd.setCursor()

D lcd.print()

The createChar() function is used to define a custom character pattern.

What is the maximum number of custom characters you can store on a standard 16x2 LCD?

A 16

B 4

C 8

D 32

The LCD can store up to 8 custom characters at once.

After creating a custom character, how do you display it on the LCD?

A Use lcd.print() with the character's ASCII code

B Use lcd.write() with the character's location number

C Use lcd.setCursor() with the character's pattern

D Use lcd.clear() then lcd.print()

You display a custom character by writing its location number (0-7) with lcd.write().

What does each byte in the array passed to createChar() represent?

A A row of pixels in the 5x8 grid

B A column of pixels in the 5x8 grid

C The brightness of the character

D The color of the character

Each byte represents one row of 5 pixels in the character's 5x8 grid.

Describe the steps to create and display a custom character on a 16x2 LCD using Arduino.

Think about defining the pattern, storing it, positioning, and then showing it.

Explain why you can only have 8 custom characters on a standard LCD at one time.

Consider the LCD's built-in memory capacity for custom characters.

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()