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.

Introduction:

The I2C address bits are selectable using the on-board solder 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 solder jumper so you can use a separate high current power supply to power the IO Pi reducing the load on the Raspberry Pi. Use of an external supply is recommended if you plan on connecting more than one IO Pi Plus to your Raspberry Pi.  The 5V input is compatible with our 5mm screw terminals.

I2C Address Selection

The MCP23017 contains three address select pins which can be tied to Vss or Vdd.  This gives 8 possible I2C addresses for each chip.  To simplify address selection on the IO Pi Plus we have included a set of address selection pads which can be configured by applying a small solder bridge across the required pads. The table below show the recommended configurations for your IO Pi Plus and the associated I2C addresses.

Note:
Disconnect the IO Pi Plus from the Raspberry Pi before changing the i2c address.  The address pins are tied to GND (low) via a 10K resistor so the jumper is used to tie a pin to Vcc (high).

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

2	1	0	Address
			0x20
			0x21
			0x22
			0x23
			0x24
			0x25
			0x26
			0x27

 

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
Raspberry Pi Zero W	Yes
ODroid C1	Yes
ODroid C2	Yes
Orange Pi	Yes
Asus Tinker Board	Yes

Features

•  32 Digital Inputs/Outputs
• Control via the Raspberry Pi I2C port
• Stack up to 4 IO Pi boards on a single Raspberry Pi
• Solder jumper selectable I2C addresses
• External 5V Input with isolation solder 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 unsoldered.  Before using the IO Pi Plus you will need to solder the connector onto the PCB.  The power link and I2C address selection are configured using solder jumpers.  For your convenience we supply the IO Pi Plus with the power link jumper and one address selection jumper presoldered.

The digital input pads are spaced 2.54mm apart.  You can solder wires directly to the board or use 2.54mm pitch headers.  The IO Pi Plus is compatible with 20 pin IDC vertical and right angle headers allowing you to use ribbon cables to connect your external devices to the board.

Watch the assembly video, best viewed in 1080p high quality mode:

PCB Header Assembly Jig

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

Installation

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

If you are installing more than one IO Pi on a single Raspberry Pi board then you will need to configure the address select jumpers for each IO Pi.

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

Schematic

Click to download schematic PDF.

Mechanical Drawings

Click image to enlarge

Code Libraries and Demos

We have Python, Arduino, C, C++, Node.js and Windows 10 IOT libraries available for this expansion board.  You can download all of the libraries from github at:

https://github.com/abelectronicsuk/ or click on the logos below for your selected programming language,

 

 

Tutorials

We have several tutorials available for the IO Pi Zero and IO Pi Plus in our Knowledge Base.

IO Pi Plus Tutorials

Legacy IO Pi Versions

See our KB article for previous versions of this board