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mcp23008-e-p-io-expander

4 min read

Important Note

This entire repo was AI created - including all of the data within. The intent was to A) help me with my personal electronics inventory; and B) see how I could use AI to make that process a bit easier. DO NOT TRUST!

MCP23008-E/P - 8-Bit I/O Expander with I2C Interface

Details

Description

The MCP23008 is an 8-bit I/O expander that provides additional GPIO pins for microcontrollers through an I2C interface. It features a single 8-bit port that can be configured independently as inputs or outputs. This IC is ideal for expanding the I/O capabilities of Arduino, Raspberry Pi, and other microcontroller systems when you need additional digital pins but want to minimize the pin usage on your main controller.

Specifications

Electrical Characteristics

  • Operating Voltage: 1.8V ~ 5.5V
  • Supply Current: 1mA (quiescent), 1µA (standby)
  • Clock Frequency: 1.7MHz (I2C)
  • Output Current: 25mA per pin
  • Logic Levels:
    • Logic Low: max 0.2 × VDD
    • Logic High: min 0.8 × VDD

Physical Characteristics

  • Package: 18-PDIP (0.300”, 7.62mm)
  • Dimensions: Standard 18-pin DIP package
  • Operating Temperature: -40°C ~ 125°C
  • Mounting Type: Through Hole

Key Features

  • 8 GPIO pins (single 8-bit port)
  • I2C interface (up to 8 devices on same bus)
  • Configurable interrupt output
  • Power-on reset (POR)
  • Push-pull outputs
  • Individual pin direction control
  • Hardware address pins for multiple devices
  • 3.3V and 5V compatible

Image

Image needed - Standard 18-pin DIP package IC with MCP23008-E/P markings on top. Consider taking a photo of actual component for documentation.

Pinout Diagram

Pin Descriptions (18-PDIP Package)

PinNameFunction
1SCLI2C clock
2SDAI2C data
3A2Address select bit 2
4A1Address select bit 1
5A0Address select bit 0
6RESETReset input (active low)
7NCNot connected
8INTInterrupt output
9VSSGround
10GP0GPIO pin 0
11GP1GPIO pin 1
12GP2GPIO pin 2
13GP3GPIO pin 3
14GP4GPIO pin 4
15GP5GPIO pin 5
16GP6GPIO pin 6
17GP7GPIO pin 7
18VDDPower supply (+1.8V to +5.5V)

Applications

Common use cases and applications for this component:

  • Arduino and Raspberry Pi GPIO expansion
  • LED control (up to 8 LEDs)
  • Button/switch input expansion
  • Sensor input expansion
  • Small relay control
  • Digital signal routing
  • Simple automation projects
  • Educational electronics projects

Circuit Examples

Basic I2C Connection

VDD (Pin 18) ---- +3.3V or +5V
VSS (Pin 9) ----- Ground
SCL (Pin 1) ----- I2C Clock (Arduino A5, RPi GPIO 3)
SDA (Pin 2) ----- I2C Data (Arduino A4, RPi GPIO 2)
RESET (Pin 6) --- VDD (or control pin)
A0-A2 (Pins 5-3) - Address selection (GND/VDD)

LED Control Example

GP0-GP7 (Pins 10-17) -> LEDs with current limiting resistors
Configure all pins as outputs in software
Each pin can drive up to 25mA

Button Input Example

GP0-GP7 (Pins 10-17) -> Buttons with pull-up resistors
Configure pins as inputs with internal pull-ups enabled
Use interrupt pin (INT) for change detection

Technical Notes

Important technical considerations and features:

  • I2C Address: Base address 0x20, configurable with A0-A2 pins
  • Multiple Devices: Up to 8 MCP23008s on same I2C bus (addresses 0x20-0x27)
  • Pull-up Resistors: Internal 100kΩ pull-ups available on all GPIO pins
  • Interrupt Capability: Single interrupt output for all pins
  • Power Supply Decoupling: Use 0.1µF ceramic capacitor near VDD pin
  • I2C Pull-ups: Require external pull-up resistors on SCL/SDA lines (4.7kΩ typical)
  • Reset Pin: Can be tied to VDD if not used for control
  • Pin Current: Maximum 25mA per pin, 125mA total for all pins

Programming Notes

  • Arduino Libraries: Available libraries like “Adafruit MCP23008” simplify usage
  • Register Access: Direct register manipulation possible for advanced control
  • Initialization: Requires setting IODIR register to configure pin directions
  • Interrupt Handling: Can trigger on pin change or compare against reference value
  • Port Operations: Can read/write entire 8-bit port or individual pins

Comparison with MCP23017

The MCP23008 is the smaller sibling of the MCP23017:

  • MCP23008: 8 GPIO pins, 18-pin package, single port
  • MCP23017: 16 GPIO pins, 28-pin package, dual ports
  • Same Interface: Both use I2C with identical addressing scheme
  • Same Features: Both support interrupts, pull-ups, and similar functionality
  • Use Case: MCP23008 for smaller projects, MCP23017 for more I/O needs

Tags

io-expander, interface-ic, i2c, gpio, microchip, mcp23008 cabinet-3 bin-38 status-available

Notes

The MCP23008 is the perfect choice when you need to add a moderate number of GPIO pins (8) to your microcontroller project without using many pins on your main controller. It’s particularly useful for smaller projects where the 16-pin MCP23017 would be overkill. The I2C interface makes it easy to integrate, and the ability to chain up to 8 devices means you can potentially add 64 GPIO pins using only two wires from your microcontroller. Having 26 of these ICs provides excellent flexibility for various small to medium-scale I/O expansion needs.

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