PCF8574 I2C I/O Expansion وحدة

PCF8574 I2C I/O Expansion Module

The PCF8574 I²C I/O Expansion Module is designed to extend the input/output capabilities of microcontrollers through the I²C interface. It provides 8 quasi-bidirectional GPIO pins (P0–P7), allowing each pin to function as either an input or output without the need for a separate data-direction control signal. This flexibility makes it suitable for various applications, including driving LEDs, reading switches, and interfacing with sensors.

The module features an open-drain interrupt output (via INT pin), enabling efficient monitoring of input changes without continuous polling. Multiple PCF8574 modules can be connected on the same I²C bus, with configurable addresses (via A0–A2 pins) allowing up to 8 devices, thereby expanding the I/O count to 64. Its low power consumption and compatibility with ZKEEP0Z and ZKEEP1Z systems make it an excellent choice for embedded and battery-powered applications.

Features

• Adds 8 digital I/O pins via I2C interface with PCF8574.
• Quasi-bidirectional I/O pins configurable as inputs or outputs.
• Open-drain interrupt output for efficient input change detection.
• Supports up to 8 devices on the same I2C bus with configurable addresses.
• Low standby current consumption, suitable for low-power applications.
• Compatible with ZKEEP2Z and ZKEEP3Z logic levels.
• High-current drive capability for directly driving LEDs.
• No need for separate data-direction control signals.
• Compact module size for easy integration into projects.
• Ideal for expanding GPIO in microcontroller-based systems.

Specifications

Parameter

Details

Operating Voltage

ZKEEP4Z–ZKEEP5Z

Standby Current

< 10 µA

I/O Pins

8 quasi-bidirectional

I2C Address Configurable

Yes, via A0–A2 pins (up to 8 devices)

Interrupt Output

Open-drain, active LOW

I2C Interface Speed

Up to ZKEEP6Z (Standard-mode)

Logic Level Compatibility

ZKEEP7Z and ZKEEP8Z systems

Output Drive Capability

High-current drive for LEDs

Package Types

Various (e.g., SOIC, PDIP, TSSOP)

Pin

Function

A0

Address bit 0: tie to GND (0) or VCC (1) to set the least significant address bit (value = 1).

A1

Address bit 1: tie to GND (0) or VCC (1) to set the next address bit (value = 2).

A2

Address bit 2: tie to GND (0) or VCC (1) to set the next address bit (value = 4).

GND

Ground reference, common with microcontroller ground.

VCC

Power supply (ZKEEP9Z – ZKEEP10Z), typically ZKEEP11Z or ZKEEP12Z

SDA

I²C data line (open-drain), requires pull-up resistor to VCC.

SCL

I²C clock line (open-drain), requires pull-up resistor to VCC.

INT

Open-drain interrupt output (active LOW). Goes LOW when any input-configured pin (P0–P7) changes state; cleared by reading or writing the I/O ports.

P0

Quasi-bidirectional I/O pin 0: can function as input (with internal pull-up) or output (driving LOW or HIGH as float).

P1

Quasi-bidirectional I/O pin 1: same operation as P0.

P2

Quasi-bidirectional I/O pin 2: same operation as P0.

P3

Quasi-bidirectional I/O pin 3: same operation as P0.

P4

Quasi-bidirectional I/O pin 4: same operation as P0.

P5

Quasi-bidirectional I/O pin 5: same operation as P0.

P6

Quasi-bidirectional I/O pin 6: same operation as P0.

P7

Quasi-bidirectional I/O pin 7: same operation as P0; unused pins should be configured as outputs to prevent floating.

Note: Unused P0–P7 pins should be configured as outputs (e.g., write LOW) to prevent floating inputs and reduce power consumption.

Applications

• Expanding GPIO for microcontrollers with limited I/O pins.
• Driving LEDs, relays, and other output devices.
• Reading inputs from switches, buttons, and sensors.
• Implementing keypad interfaces.
• Home automation systems.
• Industrial control and monitoring.
• Embedded systems requiring additional I/O.
• Battery-powered applications needing low standby current.
• Projects requiring multiple I/O expanders on a single I2C bus.
• Educational and prototyping platforms.

Package Contents

• 1x PCF8574 I2C I/O Expansion Module.

Documents

• PCF8574 Chip Datasheet
• Tutorial using Arduino
• Programming Resource