Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout

The Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout combines versatility and compact design, making it a superior I2C GPIO expander and keypad matrix driver. It features 18 I/O pins, arranged as 10 columns and 8 rows, supporting a matrix of up to 80 buttons or individual GPIO functionalities.

The built-in 10-element event queue ensures keypress and release events are held if not immediately addressed, providing robust input management. Operating via I2C, this expander integrates seamlessly with various microcontrollers and computers.

For GPIO expansion, all pins are configurable as input/output, with optional pull-ups and interrupt capabilities. A debouncer offers low-pass filtering for cleaner tactile switch signals. Outputs efficiently manage LED drivers with high/low settings.

In keypad matrix mode, pull-ups and scanning are automated, and a 10-element FIFO queue records key events. Interrupts on key actions reduce the need for constant polling. Libraries for Arduino and CircuitPython are available for broad compatibility, and a Linux Kernel driver is offered for single-board computer support.

The custom-made PCB follows the STEMMA QT form factor, simplifying integration. Equipped with a 3.3V regulator and I2C line level shifting, it's compatible with 3V or 5V microcontrollers. Its connectors match SparkFun Qwiic I2C connectors for easy, solderless chaining with other devices.