MCP23017 16 Bit I2C/SPI IO Expander Module

This MCP23017 I/O expander module solves one of the most common headaches in microcontroller projects: running out of GPIO pins. It adds a full 16 bidirectional input/output lines to your Arduino, Raspberry Pi, ESP32 or STM32 project while using just two wires over I2C, or a fast four-wire SPI connection if you populate the board with the SPI-variant chip instead. Three onboard address pins let you set a unique bus address, so up to eight of these modules can share the same I2C or SPI bus, giving a single controller access to as many as 128 extra pins for switches, LEDs, relays, keypads and sensor arrays. Each port includes configurable interrupt outputs that can flag a pin change without the host constantly polling, along with a polarity inversion register and an external reset input for more reliable, lower-overhead designs. Running on a wide 1.8V to 5.5V supply with barely any standby current draw, it fits comfortably into both 3.3V and 5V systems and battery-powered builds alike. This makes it a practical choice for home automation panels, robotics controllers, test rigs, and any hobby or prototyping project that has simply run out of pins on the main board. Compact, well-documented and widely supported by existing Arduino and Python libraries, it’s an efficient way to scale up I/O without adding a second microcontroller.

Specification:

• Chip : MCP23017 (I2C) / MCP23S17 (SPI)
• IO Pins : 16 (Bidirectional)
• I2C Speed : 100kHz / 400kHz / 1.7MHz
• SPI Speed : Up to 10MHz
• Address Pins : 3 (Up to 8 Devices per Bus)
• Interrupt Output : INTA & INTB, Configurable
• Operating Voltage : 1.8V to 5.5V
• Standby Current : 1 µA (Max)