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The AB Electronics UK Knowledge Base provides support solutions, tutorials and troubleshooting guides.

Knowledge Base

IO Pi Plus 1.0 (Discontinued)

IO Pi Plus 1.0 Legacy version information

IO Pi Plus Legacy version

The IO Pi Plus version 1.0 has been updated to a new 2.1 version which you can purchase from

The IO Pi Plus is a 32-channel digital expansion board designed for use on the Raspberry Pi. The board is based around the MCP23017 16-bit I/O expander from Microchip Technology Inc. A pair of MCP23017 expanders are included on the board, allowing you to connect up to 32 digital inputs or outputs to the Raspberry Pi. The IO Pi Plus Expander is powered through the host Raspberry Pi using the GPIO port, and extended pins on the GPIO connector allow you to stack the IO Pi Plus along with other expansion boards.

The I2C address bits are selectable using the onboard jumpers. The MCP23017 supports up to 8 different I2C addresses, so with two MCP23017 devices on each IO Pi, you can stack up to 4 IO Pi boards on a single Raspberry Pi, giving a maximum of 128 I/O ports.

The IO Pi includes a 5V port that can be isolated from the Raspberry Pi via an isolation jumper. You can use a separate high-current power supply to power the IO Pi, reducing the load on the Raspberry Pi. The use of an external supply is recommended if you plan on connecting more than one IO Pi to your Raspberry Pi.

I2C Address Selection

The MCP23017 contains three address select pins, which can be tied to Vss, Vdd.  This gives 8 possible I2C addresses for each chip. The IO Pi includes two MCP23017 chips, so you can stack up to 4 IO Pi boards on a single Raspberry Pi. To simplify address selection on the IO Pi, we have included a set of address selection pins which can be configured using the included jumpers. The illustrations below show the four recommended configurations for your IO Pi and the associated I2C addresses.

Disconnect the IO Pi from the Raspberry Pi before changing the address pins. The address pins are tied to Vdd (high) via a 10K resistor, so the jumper connects a pin to ground (low).

Default Configuration (IC1 = 0x20, IC2 = 0x21)

When you purchase the IO Pi, the address selection jumpers will be pre-configured to the following addresses. IC1 Port = I2C Address: 0x20, IC2 Port = I2C Address: 0x21

Default I2C config

Recommended Address Configurations

Configuration 1: 
IC1 Port = I2C Address: 0x20
IC2 Port = I2C Address: 0x21

Config 1

Configuration 2: 
IC1 Port = I2C Address: 0x22
IC2 Port = I2C Address: 0x23

Config 2

Configuration 3: 
IC1 Port = I2C Address: 0x24
IC2 Port = I2C Address: 0x25

Config 3

Configuration 4: 
IC1 Port = I2C Address: 0x26
IC2 Port = I2C Address: 0x27

Config 4

Compatibility Chart

Model Status
Raspberry Pi Model A No
Raspberry Pi Model B No
Raspberry Pi 1 Model A+ Yes
Raspberry Pi 1 Model B+ Yes
Raspberry Pi 2 Model B Yes
Raspberry Pi 3 Model B Yes
Raspberry Pi Zero Yes
ODroid C1 Yes
ODroid C2 Yes



  •  32 Digital Inputs/Outputs
  • Control via the Raspberry Pi I2C port
  • Stack up to 4 IO Pi boards on a single Raspberry Pi
  • Jumper selectable I2C addresses
  • External 5V Input with isolation jumper
  • Based on the MCP23017 from Microchip Technologies Inc
  • Configurable interrupt output pins - Configurable as active-high, active-low or open-drain
  • INTA and INTB can be configured to operate independently or together
  • Configurable interrupt source  - Interrupt-on-change from configured register defaults  or pin changes
  • Polarity Inversion register to configure the polarity of the input port data

Input Ratings & Specifications

Vdd (5V input pin when isolation jumper is removed): 4.5V - 5.5V
All digital inputs and outputs: 0 - Vdd
Current at I/O Pin (sourced or sunk): 25 mA
Maximum current on a single I/O Bank (1 MCP23017 device): 125 mA

Assembly Instructions

The IO Pi Plus is supplied with the 40-pin GPIO connector, power jumper, and the unsoldered 12-pin address connector. 

Before using the IO Pi Plus, you must solder both connectors onto the PCB. We suggest soldering the 40-pin GPIO connector first, then the address select connector, and then the power jumper. 

PCB Header Assembly Jig

Download and print our PCB Header Assembly Jig to hold your circuit board when soldering the header pins.

How to use the assembly jig


To install the IO Pi, press the 40-pin connector down onto the Raspberry Pi GPIO pins with the board sitting over the top of the Raspberry Pi.

If installing more than one IO Pi on a single Raspberry Pi board, you must configure the address select jumpers for each IO Pi.

Remove the isolation jumper when connecting an external power supply to the 5V port.


Click to download
Click to download the schematic PDF.

Mechanical Drawings

Click the image to enlarge

Sample Code

Arduino, C, Windows 10 IOT, and Python libraries are available for this expansion board. You can download all of the libraries from GitHub at:

Download the Arduino libraries from:

To download the C libraries to your Raspberry Pi, type in the terminal:

git clone

To download the Python libraries to your Raspberry Pi, type in the terminal:

git clone

Download the Windows 10 IOT libraries from:

Download Python 2 and 3 code samples

Download Arduino code samples


Our Knowledge Base has several tutorials for the IO Pi Zero and IO Pi Plus.

IO Pi Tutorials

Legacy IO Pi Versions

See our KB article for previous versions of this board.

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Created 10/02/2017 | Last Updated: 01/01/2024

Related Expansion Boards

Order a IO Pi Plus Photo of IO Pi Plus
IO Pi Plus

32 channel MCP23017 digital I/O expander for the Raspberry Pi

£14.39 Ex VAT: £11.99
Add to Cart

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