The Adafruit PCF8575 GPIO Expander is an inexpensive I2C expander that provides 16 additional GPIO channels for projects where onboard I/O pins are insufficient. The device enables control of multiple buttons, LEDs, and other peripherals using only two I2C pins. Multiple expanders can be chained—up to 8 units on a single bus—adding up to 64 GPIOs.

The PCF8575 operates somewhat differently from the more common MCP230xx series expanders:

• 16 I/O pins
• With three address jumper wires, up to 8 expanders on a single I2C bus
• Each pin can act as an input with a light internal pull-up or as a strong ground-driving output
• An IRQ output automatically signals when an input changes
• No separate direction register – pin state is determined by how they are driven

For example, reading a button is done by connecting it between a PCF pin and ground. An LED is driven by connecting its anode to voltage through a resistor and using the pin as the cathode. Libraries for Arduino and CircuitPython make usage easier.

The module is implemented in the STEMMA QT format, which is compatible with SparkFun Qwiic connectors. This allows easy solderless connection and chaining of other I2C devices.

Product dimensions:

• Size: 40.8 mm x 17.7 mm x 4.5 mm
• Weight: 2.6 g

Package includes:

• Adafruit PCF8575 GPIO expansion board
• Header pins

Links:

• Product information page
• PCF8575 Datasheet (PDF)