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The Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout is a versatile I2C GPIO expander and keypad matrix driver. With 18 I/O pins (10 columns and 8 r...

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The Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout is a versatile I2C GPIO expander and keypad matrix driver. With 18 I/O pins (10 columns and 8 rows), it can manage up to 80 switches in a matrix configuration or serve as individual GPIO inputs and outputs.

Whether you need more buttons, LEDs, or a full keypad matrix for your project, this breakout handles it all over a simple I2C connection. It features a 10-element event queue so key presses and releases are stored even if you can't respond to the interrupt immediately. The built-in STEMMA QT connectors and onboard 3.3V regulator with level shifting make it compatible with both 3V and 5V microcontrollers.

Key Features

  • 18 I/O Pins – 10 columns and 8 rows, configurable as a keypad matrix (up to 80 switches) or individual GPIO
  • 10-Element FIFO Event Queue – Stores key press and release events so you never miss an input
  • I2C Interface – Easy to connect and share the bus with other sensors and devices
  • GPIO Inputs with Pull-ups – Optional pull-up resistors, interrupt output on INT pin for rising or falling signals, and built-in debouncer for noisy tactile switches
  • GPIO Outputs – Set pins high or low for basic LED driving
  • Interrupt Support – Configurable interrupt output on key press or release, no need for constant polling
  • STEMMA QT / Qwiic Compatible – Solderless STEMMA QT connectors on both sides, compatible with SparkFun Qwiic
  • Onboard Voltage Regulation – Built-in 3.3V regulator and I2C level shifting for 3V or 5V microcontrollers

Ideal For

  • Custom keypads and button matrices
  • Expanding GPIO on pin-limited microcontrollers
  • LED control arrays
  • Projects requiring interrupt-driven button input
  • I2C sensor and peripheral chains

Package Contents

  • 1× Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout
Note: A STEMMA QT / Qwiic cable is required for solderless connection and is not included. Browse our range of Qwiic cables to find one that suits your setup.

Resources

Jargon buster

Plain-language definitions for the technical terms used above.

3.3V regulator
A 3.3V regulator is a power circuit that provides a steady 3.3 volts for parts that need that supply voltage. On a breakout board, it can let the sensor run safely even when the connected microcontroller or power source uses a higher voltage.
breakout
A breakout is a small circuit board that makes a tiny or hard-to-solder component easier to connect to with standard pins. It matters because this OLED module can be wired into a microcontroller project without needing to solder directly to the display’s fine contacts.
FIFO
FIFO stands for “first in, first out” and is a small memory buffer inside the sensor that stores recent readings in order. This matters because it can help capture motion data without the microcontroller needing to read the sensor every single instant.
GPIO
General-purpose input/output pins are microcontroller pins you can set in software to read signals, switch devices on and off, or connect to peripherals. The number of GPIO pins matters because it limits how many buttons, LEDs, sensors, and other parts you can wire directly to the board.
I2C
I2C is a two-wire communication bus used by many sensors and small modules. It matters because several I2C devices can share the same two wires, but each device needs a compatible address and your controller must support I2C.
LED
A light-emitting diode is a small electronic component that lights up when current flows through it in the correct direction. In this kit, LEDs create the flashing effect, so polarity and correct soldering matter for the project to work.
Qwiic
Qwiic is a plug-in connector system for I2C devices that uses small 4-pin cables, so you can connect compatible sensors without soldering. It matters because your controller or adapter also needs Qwiic, or you will need a cable or breakout to wire it up.
STEMMA
A plug-and-cable connection system used on some maker electronics boards to make wiring simpler. If a product uses STEMMA, you need the matching cable or connector type to plug it in without soldering.
STEMMA QT
A small plug-in connector system for I2C boards that lets you connect compatible sensors and controllers without soldering. It matters because it can make wiring faster and less error-prone, especially when adding several small modules to a project.
UPS
An uninterruptible power supply is a battery-backed power system that keeps a device running when external power is unplugged or fails. For an embedded computer, it helps prevent sudden shutdowns that can corrupt files or interrupt a project.

Related Tutorials

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