16×2 LCD I2C: Custom Characters and Menu System

The 16×2 character LCD is arguably the most widely used display in the maker community — and for good reason. It is affordable, easy to programme, and displays text clearly. Adding an I2C backpack reduces the wiring from 12+ pins to just 4 wires. In this guide, we go beyond the basics to cover custom character creation and building a proper menu navigation system.

Understanding the 16×2 LCD with I2C Backpack

The 16×2 LCD based on the HD44780 controller displays 2 lines of 16 characters each. The I2C backpack (PCF8574 or PCF8574T) sits on the back and converts the parallel interface to I2C:

• Only 4 wires needed: VCC, GND, SDA, SCL
• Default I2C address: 0x27 (some modules use 0x3F)
• Backlight control: Managed via I2C — no extra pin needed
• Contrast adjustment: Small potentiometer on the I2C board

This combination of simplicity and capability makes it the default choice for projects that need text output — from temperature displays to 3D printer controllers.

Wiring and Initial Setup

Install the LiquidCrystal_I2C library and run this test:

#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Hello, Zbotic!");
  lcd.setCursor(0, 1);
  lcd.print("Made in India");
}

If you see a blank screen with backlight on, adjust the contrast potentiometer with a small screwdriver.

Creating Custom Characters

The HD44780 controller supports up to 8 custom characters (5×8 pixels each), stored in CGRAM. Here is how to create them:

// Heart symbol
byte heart[8] = {
  0b00000,
  0b01010,
  0b11111,
  0b11111,
  0b11111,
  0b01110,
  0b00100,
  0b00000
};

void setup() {
  lcd.init();
  lcd.backlight();
  lcd.createChar(0, heart);
  lcd.setCursor(0, 0);
  lcd.write(byte(0)); // Display the heart
}

Useful custom characters for Indian projects:

• Rupee symbol (₹) — essential for billing/pricing displays
• Temperature icon — thermometer shape for weather stations
• Battery level indicators — empty, quarter, half, three-quarter, full
• Arrow symbols — for menu navigation indicators
• Lock/unlock icons — for security systems

Use online tools like LCD Character Creator to design your custom characters visually.

Building a Multi-Page Menu System

A menu system transforms a simple LCD into an interactive user interface. Here is the architecture:

const char* menuItems[] = {
  "1. Temperature",
  "2. Humidity",
  "3. Set Alarm",
  "4. WiFi Config",
  "5. About"
};
int menuIndex = 0;
int totalItems = 5;

void displayMenu() {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(">");
  lcd.print(menuItems[menuIndex]);
  lcd.setCursor(0, 1);
  if (menuIndex + 1 < totalItems) {
    lcd.print(" ");
    lcd.print(menuItems[menuIndex + 1]);
  }
}

Use two buttons (Up/Down) or a rotary encoder to navigate. The “>” cursor indicates the currently selected item. Press a “Select” button to enter a sub-menu or execute an action.

Using Rotary Encoder for Navigation

A rotary encoder with a built-in push button is the most elegant navigation solution:

• Rotate clockwise — move down the menu
• Rotate anti-clockwise — move up the menu
• Press the knob — select/enter the current item
• Long press — go back to the previous menu level

This gives you a professional-feeling interface with just a single knob — similar to car infotainment systems or 3D printer controllers. Use the Encoder library with interrupt-driven reading for smooth, debounce-free rotation detection.

Displaying Sensor Data with Custom Icons

Combine custom characters with sensor readings for a polished dashboard:

• Line 1: [thermometer icon] 28.5°C [droplet] 65%
• Line 2: [clock icon] 14:30 [bell] Alarm ON

This approach packs maximum information into 32 characters while remaining highly readable. Update the display every 2 seconds to keep readings current without causing LCD flicker.

Common Troubleshooting Tips

• Blank screen with backlight: Adjust the contrast potentiometer; try I2C address 0x3F
• Garbled characters: Check wiring, especially SDA and SCL; run an I2C scanner to verify address
• Flickering display: Add a 100 µF capacitor across VCC and GND near the LCD
• I2C address conflicts: If using multiple I2C devices, ensure no address overlap; some PCF8574 boards have solder jumpers to change address
• Custom characters disappearing: You must call createChar() in setup, and characters are lost after lcd.clear() on some libraries — recreate them after clearing

Recommended LCD Modules from Zbotic

These are our best-selling LCD modules for your next project: