🌱 LCD Custom Character Generator for HD44780

Design custom characters for HD44780-compatible LCD displays. Click pixels to toggle them on/off, then copy the generated Arduino code.

LCD Preview:

Binary (0b) Hexadecimal (0x)

LCD Pin Configuration

LCD Pin	Arduino Pin
RS
Enable
D4
D5
D6
D7

🔌 Wiring Diagram: Arduino to LCD Connection

LCD Module (HD44780)

VSS → GND

VDD → +5V

V0 → Contrast

RS → Pin 12

RW → GND

E → Pin 11

D4 → Pin 5

D5 → Pin 4

D6 → Pin 3

D7 → Pin 2

A → +5V

K → GND

LCD Pin	Type	Connection	Description
VSS	Power	Arduino GND	Ground connection for the LCD module
VDD	Power	Arduino 5V	Power supply (+5V) for the LCD logic
V0	Power	Potentiometer (10kΩ)	Contrast adjustment - connect to middle pin of potentiometer between 5V and GND
RS	Control	Arduino Pin 12	Register Select - LOW for commands, HIGH for data
RW	Control	Arduino GND	Read/Write - connect to GND for write-only mode (most common)
E	Control	Arduino Pin 11	Enable - triggers data read/write on falling edge
D0-D3	Optional	Not connected	Data pins 0-3 - unused in 4-bit mode
D4	Data	Arduino Pin 5	Data bit 4 - used in 4-bit communication mode
D5	Data	Arduino Pin 4	Data bit 5 - used in 4-bit communication mode
D6	Data	Arduino Pin 3	Data bit 6 - used in 4-bit communication mode
D7	Data	Arduino Pin 2	Data bit 7 - used in 4-bit communication mode
A	Power	Arduino 5V (via 220Ω resistor)	Backlight anode (+) - use resistor to limit current
K	Power	Arduino GND	Backlight cathode (-) - ground for backlight LED

💡 Pro Tip: The pin numbers shown above are defaults and can be customized in the Pin Configuration table. 4-bit mode uses only D4-D7, saving 4 Arduino pins while maintaining full functionality.

How It Works: Understanding LCD Custom Characters ▼

HD44780 LCD displays support up to 8 custom characters (positions 0-7), each defined as a 5×8 pixel matrix. Each row is stored as a single byte where the 5 rightmost bits represent the pixel states.

Binary to Pixel Mapping

Each row is encoded as a byte. For example, 0b11111 (binary) or 0x1F (hex) represents all 5 pixels turned on:

Binary: 0b11111
Hex: 0x1F
Decimal: 31

Visual:

Bit Position Breakdown

Each bit position corresponds to a pixel column (right to left):

• Bit 4 (16): Leftmost pixel
• Bit 3 (8): Second pixel
• Bit 2 (4): Center pixel
• Bit 1 (2): Fourth pixel
• Bit 0 (1): Rightmost pixel

Example: Heart Character

A heart symbol might be encoded as:

byte heart[] = {
  0b00000,  // Row 1: ░░░░░
  0b01010,  // Row 2: ░█░█░
  0b11111,  // Row 3: █████
  0b11111,  // Row 4: █████
  0b01110,  // Row 5: ░███░
  0b00100,  // Row 6: ░░█░░
  0b00000,  // Row 7: ░░░░░
  0b00000   // Row 8: ░░░░░
};

Using Custom Characters

After defining your character array, load it into the LCD and display it:

lcd.createChar(0, heart);  // Load into position 0
lcd.setCursor(0, 0);        // Set cursor position
lcd.write(byte(0));         // Display character from position 0

Memory Note: Custom characters are stored in CGRAM (Character Generator RAM) and persist until power off or overwritten.

Resources & Documentation

• 📘 LCD 16x2 Display Module Tutorial (Vietnamese)
• 📖 Arduino LiquidCrystal Library Reference
• 📄 HD44780 Datasheet (PDF)
• 🔧 Arduino LCD Display Guide
• 💡 Custom Character Example Sketch