Overview
The PCF8574 IO Expansion Board is an 8-bit remote I/O expander for the I2C-bus. It provides a simple solution when you need additional inputs or outputs for your microcontroller. This is the same chip often found on the back of I2C LCD modules, but in a standalone format that allows you to trigger relays, read switches, or drive LEDs. Because it supports I2C cascading, you can connect multiple boards in series to create a massive I/O matrix without wasting your controller’s precious pins.
Key Features
I2C Interface: Only uses 2 pins (SDA/SCL) to control 8 separate digital ports.
Bidirectional I/O: Each of the 8 pins can be used as either an input or an output.
Daisy-Chain Support: Features pin headers that allow you to plug one module into another to expand up to 64 I/O points.
Address Jumpers: Integrated jumpers/dip-switches to easily change the I2C address ($0\times20$ to $0\times27$).
Interrupt Output: Includes an “INT” pin that alerts your microcontroller when an input state changes, saving CPU power.
Technical Specifications
| Feature | Specification |
| Operating Voltage | 2.5V to 6.0V DC |
| Interface | I2C (Standard & Fast mode) |
| I/O Pins | 8 Bits (Bidirectional) |
| Max Current per Pin | 25mA (Sink) / 10mA (Source) |
| Standby Current | 10µA (Ultra-low power) |
| Logic Type | Open-drain interrupt output |
| Dimensions | 48mm x 16mm |
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