MCP23017 16-Bit I/O Port Expander IC – I2C GPIO Expander, DIP-28

The MCP23017 16-Bit I/O Port Expander IC is designed to increase the number of digital inputs and outputs available to a microcontroller without requiring a large number of additional MCU pins. The MCP23017 communicates over I2C and provides 16 GPIO pins arranged as two 8-bit ports.

The device supports a wide 1.8V to 5.5V supply range and I2C communication modes of 100kHz, 400kHz, and up to 1.7MHz, with the higher-speed modes subject to the supply-voltage conditions specified in the datasheet.

Each GPIO can be configured for digital input or output operation. The device also provides internal weak pull-ups, interrupt capability, and power-on reset features, making it suitable for control panels, keypads, switches, indicators, display interfaces, and other GPIO-intensive embedded applications.

Features

• 16-bit bidirectional I/O port expander
• 16 configurable digital I/O pins
• Two 8-bit GPIO ports: Port A and Port B
• I2C serial interface
• Supports 100kHz, 400kHz, and up to 1.7MHz I2C operation
• Wide 1.8V–5.5V supply range
• Three hardware address pins: A0, A1 and A2
• Up to 8 MCP23017 devices on one I2C bus
• Up to 128 expanded I/O lines using eight uniquely addressed devices
• Dual configurable interrupt outputs, INTA and INTB
• Power-on reset
• Internal GPIO pull-up capability
• MCP23017-E/SP available in 28-pin SPDIP through-hole package

Applications

• Arduino GPIO expansion
• Arduino Nano and other pin-limited MCU projects
• ESP32 and Raspberry Pi GPIO expansion
• Large button and switch interfaces
• Matrix keypad projects
• LED and indicator control
• Display and instrumentation panels
• Relay-control interfaces with suitable driver circuits
• Industrial monitoring and automation
• Robotics and mechatronics
• Embedded-system prototyping

How to Use

1. Connect VDD to the appropriate supply voltage and VSS to ground.
2. Connect SDA and SCL to the microcontroller's I2C bus.
3. Configure A0, A1, and A2 to establish the required device address.
4. Connect the required GPIO pins from GPA0–GPA7 and GPB0–GPB7 to your external circuitry.
5. Configure the MCP23017 registers through I2C according to whether each pin will be used as an input or output.
6. Use INTA/INTB when interrupt-driven input detection is required.
7. Add suitable I2C pull-up resistors according to the bus voltage, capacitance, speed, and other devices on the bus.

Important Notes

• The MCP23017 is the I2C version. The MCP23S17 is the corresponding SPI-interface device.
• The official MCP23017 supply range is 1.8V–5.5V, rather than 2.7V–5.5V.
• The commonly cited 25mA source/sink figure is a maximum capability specification, not a recommendation to continuously operate every GPIO at that current. Microchip's electrical characteristics specify output-voltage conditions at lower test currents, so external driver circuitry should be used for substantial loads.
• Do not drive relays, motors, solenoids, or other high-current/inductive loads directly from the MCP23017. Use a suitable transistor, MOSFET, driver IC, or relay-driver circuit.
• I2C requires appropriate pull-up resistors on SDA and SCL. The required resistance depends on bus capacitance, speed, supply voltage, and connected devices.
• Do not leave A0, A1, or A2 floating when a defined device address is required.
• The maximum I2C speed is not universally available at every supply voltage; Microchip specifies voltage conditions for the 1.7MHz mode.
• This is a bare IC, so correct PCB design, decoupling, I2C pull-ups, grounding, and register configuration are required for reliable operation.
• Handle the IC using appropriate ESD precautions.
• The MCP23017-E/SP is a 28-pin through-hole SPDIP package; other MCP23017 variants are available in different package styles.
• Product/package markings may vary by manufacturing batch and stock source.

Package Includes

• 1 × MCP23017 16-Bit I/O Port Expander IC – DIP-28