I/O ports play a significant role in microcontrollers' functionality as it is the gateway for devices to be operated, as well as to read data from sensors. A microcontroller has a limited number of I/O pins, but there is a way to get more of these pins for a larger project.

This MCP23017 chip is an I/O expander that could add 16 I/O pins to your microcontroller. You can set each pin as an input or output, or an input pullup. You can even get an interrupt via an external pin when any of the inputs change so you don't have to keep polling the chip.

This chip requires 3V to 5V power supply. The I/O pins can drive up to 20mA, making it work well with LEDs and other components. It could be integrated into your MCU using the I2C interface. Eight of this chip could work together using a single bus as the I2C address of this chip could be modified by tying up the ADDR0-2 pins to ground. You could also integrate this module using the SPI interface.

It is compatible with Arduino boards, as well as Raspberry Pi microcomputers, and can suitable for projects that require a lot of I/O pins.