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 3.3 V and 5 V 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 3.3V and 5V 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 | 2.5 V–6 V |
| 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 100 kHz (Standard-mode) |
| Logic Level Compatibility | 3.3 V and 5 V 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 (2.5 V – 6 V), typically 3.3 V or 5 V |
| 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.
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