GPIO Expander PCAL6416A Breakout

GPIO Expander PCAL6416A Breakout is built around NXP's PCAL6416A, a 16-bit I2C GPIO expander that adds 16 programmable input/output pins to a microcontroller over two I2C wires. The 16 pins are split into two 8-bit ports, Port A and Port B, and each pin supports an individually configurable 100 kOhm pull-up or pull-down resistor along with input latching. A soldered Arduino library is available for reading and writing the expanded pins.

It's a common choice when a microcontroller runs out of GPIO pins: reading a bank of buttons or switches, driving a set of LEDs or relays directly, or building a keypad matrix, all through the same two I2C wires you may already be using for other Qwiic boards.

The board communicates over I2C in both standard mode (100 kHz) and fast mode (400 kHz), at a default address of 0x20 that can be changed to 0x21 by cutting the JP3. An active-low interrupt output on the INT pin notifies the host microcontroller whenever an input changes state, removing the need to poll every pin individually. It includes a Qwiic connector for solderless wiring alongside the standard pin headers.

Each output pin can sink up to 25 mA, enough to drive an LED directly. Typical supply current is 1.1 mA, with a maximum of 1.5 mA. Onboard jumpers select between 5V and 3.3V I2C pull-ups and can bypass the onboard voltage regulator when needed. The board measures 22 x 38 mm, with two mounting holes sized for M3 screws.