The PCF8574T I2C I/O Extension Board is a compact and powerful GPIO expander module that helps you add extra digital input/output pins to Arduino, ESP32, Raspberry Pi Pico, and other microcontrollers using only two I2C wires (SDA & SCL). It is based on the PCF8574T 8-bit I/O expander IC and is widely used for connecting LCD displays, multiple buttons, relays, LEDs, and sensors when GPIO pins are limited.
Core Module Features
• IC Used: PCF8574T (8-bit I2C GPIO expander)
• Total GPIO Pins: 8 digital I/O (P0 to P7)
• Communication Protocol: I2C (2-wire interface)
• Address Selection: Configurable using A0, A1, A2 jumpers
• Expandable Setup: Multiple modules can run on the same I2C bus
Electrical & Interface
• Operating Voltage: 2.5V – 6V DC (supports 3.3V and 5V systems)
• I2C Pins: SDA, SCL
• Power Pins: VCC, GND
• Output Type: Digital I/O (input or output configurable)
• Logic Compatibility: Works with Arduino / ESP32 / Raspberry Pi Pico
• Default I2C Address Range: 0x20 to 0x27 (based on jumper settings)
Performance & Functionality
• Adds 8 extra GPIO using only 2 MCU pins
• Supports input reading and output control
• Ideal for low-speed digital expansion tasks
• Stable communication through I2C bus
• Perfect for LCD I2C backpack and multi-button interfaces
Physical & Integration
• Compact board size for easy mounting
• Pin headers for quick breadboard connection
• Jumper pads included for address configuration
• Suitable for DIY electronics and embedded development
Applications
• I2C LCD Interface (16x2 / 20x4 LCD with I2C)
• Expanding GPIO pins on Arduino/ESP32/Pico
• Controlling multiple LEDs or relays
• Reading multiple push buttons / switches
• DIY home automation projects
• Robotics sensor and digital control expansion
Pro Tip
• If multiple I2C devices are connected, ensure each has a unique address
• Use pull-up resistors on SDA/SCL if your controller board doesn’t include them
• Best for digital switching tasks (not for PWM/analog signals)
Package Includes
• 1 × PCF8574T I2C I/O Extension Board