The Adafruit GPIO Expander Bonnet adds 16 extra digital I/O pins to your Raspberry Pi over I²C. Based on the MCP23017 chip, it plugs directly onto the Pi's 40-pin header and communicates via SDA/SCL, leaving your other GPIO pins free. Each pin can be configured as a digital output (up to 20 mA per pin) or as an input with optional internal pull-up resistors.

By default, the expander runs at 5V logic (with level-shifted I²C at 3.3V), making it suitable for driving white, blue, or green LEDs that may not work reliably at 3.3V. A solder jumper lets you switch to 3.3V logic if needed. With address select jumpers, you can stack up to 8 bonnets on a single Pi for a total of 128 additional GPIO pins.

Key Features

• 16 Extra Digital I/O Pins – Grouped into two 16-pin connectors, each with a matching ground pin
• MCP23017 I²C GPIO Expander – Controlled via SDA/SCL, no extra GPIO pins consumed
• Output: Up to 20 mA Per Pin – Drive LEDs directly (recommended total under 125 mA for the chip)
• Input with Internal Pull-Ups – Connect buttons and switches without extra resistors
• Interrupt Support – INTA and INTB pins available for solder connections to detect GPIO changes
• 5V or 3.3V Logic – Default 5V logic with solder jumper option for 3.3V
• Stackable – Address select jumpers (0x20–0x27) allow up to 8 bonnets for 128 GPIO total
• CircuitPython Support – Python 3 library for quick setup and configuration

Ideal For

• Raspberry Pi projects needing more digital I/O pins
• LED control arrays and indicator panels
• Button matrix and switch input expansion
• Multi-sensor and multi-actuator setups

Package Contents

• 1× Adafruit GPIO Expander Bonnet – Assembled and tested with slim 2×20 header
• 2× 16-pin IDC sockets (unsoldered, for optional installation)

Resources

• Adafruit GPIO Expander Bonnet Learn Guide
• CircuitPython MCP230xx Library (GitHub)