IO Zero 32

£14.99 each (including VAT: £17.99)
Product Code:IOZero32
103 in stock to order today.
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  •  32 Digital Inputs/Outputs
  • Control via the Raspberry Pi I2C port
  • Stack up to 4 IO Zero 32 boards on a single Raspberry Pi
  • Solder jumper selectable I2C addresses
  • External 3.3V to 5V Voltage Input with isolation solder jumper
  • Based on the PCA9535 from NXP
  • Interrupt pins - Open drain interrupt outputs trigger when an input pin changes state
  • Polarity Inversion register to configure the polarity of the input port data

The IO Zero 32 is a 32 channel digital expansion board designed for use on the Raspberry Pi. The board is based around the PCA9535 16-bit I/O expander from NXP. A pair of PCA9535 expanders are included on the board allowing you to connect up to 32 digital inputs or outputs to the Raspberry Pi.  The IO Zero 32 is powered through the host Raspberry Pi using the GPIO port and extended pins on the GPIO connector allow you to stack the IO Zero 32 along with other expansion boards.

The I2C address bits are selectable using the on-board solder jumpers. The PCA9535 supports up to 8 different I2C addresses so with two PCA9535 devices on each IO Zero 32 you can stack up to 4 IO Zero 32 boards on a single Raspberry Pi giving a maximum of 128 I/O ports.

The IO Zero 32 includes a voltage input port that can be isolated from the Raspberry Pi via an isolation solder jumper marked "Link" on the PCB so you can use a separate high current power supply to power the IO Zero 32 reducing the load on the Raspberry Pi. When used with an external power supply the IO Zero 32 supports a voltage range of 3.3V to 5V.  The voltage input port is compatible with our 5mm screw terminals.

To use the IO Zero 32 externally from the Raspberry Pi you will need to connect the 3.3V (Pin 1), SDA (Pin 3), SCL (Pin 5) and Ground (Pin 6) pins from the Raspberry Pi GPIO header to the corresponding pins on the IO Zero 32.  The 5V pin will also need to be connected if you are not using an external power supply.


Code Libraries and Demos

We have Python, C, C++, Node.js and .Net Core libraries available for this expansion board.  You can download all of the libraries from github at: or click on the logos below for your selected programming language,


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 & 3+ Yes
Raspberry Pi 4B Yes
Raspberry Pi Zero Yes
Raspberry Pi Zero W / Zero 2 W Yes
Orange Pi Yes
Asus Tinker Board Yes
Odroid Yes
Product thumb
IO Zero 32
£14.99 each (including VAT: £17.99)


Input / Output Ratings & Specifications

Vdd (when disconnected from 5V pin GPIO header)
3.3V - 5.5V
All digital inputs and outputs:
0 - Vdd
Maximum output current for an individual I/O Pin:
50 mA
Maximum overall current on a single I/O Bank (1 PCA9535 device):
160 mA
Interrupt maximum current:
3 mA

For a full list of PCA9535 specifications see pages 19 and 20 on the PCA9535 Datasheet

3D CAD Model

Click to downloadIO Zero 32 - 3D CAD File (STEP Format)


Click to download
Click to download schematic PDF.

Mechanical Drawings

Mechanical Drawing

Product thumb
IO Zero 32
£14.99 each (including VAT: £17.99)


The IO Zero 32 is supplied with the 40 pin GPIO connector unsoldered.  Before using the IO Zero 32 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 Zero 32 with the power link jumper and one address selection jumper pre-soldered.

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 Zero 32 is compatible with 40 pin IDC vertical and right angle headers allowing you to use ribbon cables to connect your external devices to the board. 

Note: When stacking the IO Zero 32 with other boards a right angle header is recommended for the I/O pins.

To install the IO Zero 32 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 Zero 32 on a single Raspberry Pi board then you will need to configure the address select jumpers for each IO Zero 32.

Remove the isolation jumper when connecting an external power supply to the V+ and GND pins.


PCB Header Assembly Jig

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


I2C Address Selection

The PCA9535 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 Zero 32 we have included a set of address selection pads which can be configured by applying a small solder bridge across the required pads. The I2C address table show the recommended configurations for your IO Zero 32 and the associated I2C addresses.

Disconnect the IO Zero 32 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)

I2C Address Table

2 1 0 Address

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Important Information

This development board/kit is intended for use for ENGINEERING DEVELOPMENT, DEMONSTRATION, OR EVALUATION PURPOSES ONLY and is not considered by to be a finished end-product fit for general consumer use. As such, the goods being provided are not intended to be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including product safety and environmental measures typically found in end products that incorporate such semiconductor components or circuit boards. Persons handling the product(s) must have electronics training and observe good engineering practice standards. This development board/kit does not fall within the scope of the European Union directives regarding electromagnetic compatibility, restricted substances (RoHS), recycling (WEEE), FCC, CE or UL, and therefore may not meet the technical requirements of these directives or other related directives. Note: documents in Portable Document Format (PDF) require Adobe Acrobat Reader 5.0 or higher to view, download Adobe Acrobat Reader or other PDF reading software for your computer or mobile device.