LCD I2C Adapter Module — PCF8574, 16x2 / 20x4 LCD Backpack

LCD I2C Adapter Module — PCF8574, 16x2 / 20x4 LCD Backpack

The LCD I2C adapter module (PCF8574 backpack) converts any standard HD44780-compatible 16x2 or 20x4 LCD display from a 16-pin parallel interface to a simple 2-wire I2C interface. Instead of using 6–8 Arduino digital pins for the LCD, you only need SDA and SCL — freeing up valuable Arduino pins for other sensors and modules. Solder directly onto the LCD’s 16-pin header.

Key Specifications

• IC: PCF8574 | Interface: I2C
• I2C address: 0x20–0x27 (3 address jumpers, 8 selectable)
• Compatible LCDs: HD44780 16x2 and 20x4 character LCDs
• Supply voltage: 3.3–5V
• Backlight control: Yes (on-board transistor)
• Contrast adjustment: On-board potentiometer
• Library: LiquidCrystal_I2C Arduino library
• Compliance: RoHS compliant

Why Choose This?

• ✅ Reduces LCD wiring from 8 pins to 2 — SDA + SCL only, freeing Arduino pins
• ✅ 8 selectable I2C addresses — use up to 8 LCD displays on one I2C bus
• ✅ On-board contrast pot — adjust LCD contrast without external components
• ✅ Backlight control — turn backlight on/off via software
• ✅ LiquidCrystal_I2C library — drop-in replacement for standard LiquidCrystal library

Typical Applications

• Arduino 16x2 LCD display with I2C (2-wire) interface
• 20x4 LCD display for Arduino data logging and menus
• Multi-LCD display projects using I2C address selection
• Raspberry Pi I2C LCD display interface
• Reducing pin usage on Arduino Nano and Pro Mini projects

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