PCF8574T I2C I/O Extension Board Module

PCF8574T I2C I/O Extension Board Module solves one of the most common limitations in microcontroller projects running out of GPIO pins. An Arduino Uno has 14 digital GPIO pins; an ESP8266 has even fewer usable ones. The PCF8574T module adds 8 more digital I/O pins to any microcontroller over just two wires SDA and SCL using the I2C protocol. Those same two wires that already connect sensors and displays can carry the PCF8574 communication as well, because I2C is a shared bus where many devices connect to the same two signal lines simultaneously.

The pcf8574t extension board works by receiving an I2C write command from the microcontroller and setting any combination of its 8 output pins HIGH or LOW in response. Reading from the module returns the current state of the 8 pins as a single byte — one bit per pin. That byte-oriented I/O approach means controlling 8 outputs requires sending a single byte over I2C rather than toggling eight individual GPIO pins, which simplifies firmware for builds with multiple digital outputs running in parallel.

The pcf8574t i2c i o extension board I2C address is configurable through three onboard address pins each can be set HIGH or LOW, giving 8 possible addresses from 0x20 to 0x27. Up to 8 PCF8574 modules share one I2C bus, adding up to 64 additional GPIO pins from two Arduino wires. Operating voltage from 3V to 5V covers both Arduino 5V and ESP32 3.3V systems without level shifting. The i2c extension board module suits LCD display backpack builds, relay bank expansion, and keypad scanning builds where GPIO count limits the project. This PCF8574T module is available on StemVolt, and its working on GPIO expansion and I2C interface project.

Related Product:

• Checkout CP2102 USB to TTL/RS232 Serial Converter Cable

Features:

• 8-bit parallel I/O expansion over two I2C wires from microcontroller
• 3V to 5V supply suits both Arduino 5V and ESP32 3.3V system builds
• Byte-oriented I/O sets all 8 pins simultaneously with one I2C write command
• 48 x 16 mm slim PCB fits breadboards and compact enclosure installations

Technical Specifications:

Applications:

• PCF8574T I2C I/O Extension Board Module expands for multi-relay control
• Extension board drives LCD display backpack over I2C in display panel
• Scans 4×4 keypad matrix from ESP8266 with limited GPIO
• I2C extension board module controls 8-LED status indicator array from single I2C bus address
• PCF8574 I2C interface module compatible ESP32 GPIO for multi-sensor data acquisition

Package Include:

• 1 x PCF8574T I2C I/O Extension Board Module