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IO Zero 32 32 channel digital I/O development board for the Raspberry Pi and Single-Board Computers

Features

  • 32 Digital I/O pins
  • Python, MicroPython, C, C++, Node.js and .Net Core libraries
  • Controlled 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 an 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 I/O development board designed for the Raspberry Pi and other compatible single-board computers. 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 development boards.

The I2C address bits are selectable using the onboard 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.

Technical Details

Input / Output Ratings & Specifications

Spec Ratings
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)

Schematic

Click to View
View schematic PDF.

Mechanical Drawings

Mechanical Dimensions for the IO Zero 32

Compatibility

The IO Zero 32 communicates over the industry-standard I²C protocol, which is supported by the vast majority of modern SBCs. If your board exposes SDA and SCL on a 40-pin GPIO header running at 3.3 V logic, the IO Zero 32 should work.

Platform Status Notes
Raspberry Pi A+ / B+ Tested Primary platform, full library support
Raspberry Pi 2 / 3 / 4 / 5 Model B Tested All variants confirmed, including 400 & 500
Raspberry Pi Zero / Zero W / Zero 2 W Tested All variants confirmed
Raspberry Pi Pico Tested Via I²C pins; use MicroPython library
Orange Pi Tested Enable I²C via board config; see our Orange Pi guide
Asus Tinker Board Tested Enable SMBus/I²C; see our Tinker Board guide
Odroid Tested I²C device node must be enabled in OS config
Other 40-pin I²C SBCs Likely compatible Any board with 3.3 V I²C on SDA/SCL and a GND + 3.3 V or 5 V supply pin should work
Using an unlisted SBC? As long as your board provides a 3.3 V I²C bus, a 3.3 V supply, and a ground connection, the IO Zero 32 will communicate correctly. Enable I²C in your OS (e.g., via armbian-config, orangepi-config, or your board's device-tree overlay), then use our Python or C library. Visit our Other Supported Platforms knowledge base page for configuration guides and community tips.

Using the IO Zero 32 Standalone or with Non-Standard Headers

The IO Zero 32 does not have to plug directly into an SBC's header. You can connect it to any microcontroller or SBC, including those with a non-40-pin layout, by wiring just four signals from the host to the IO Zero 32 header:

3.3 V Pin 1
SDA Pin 3
SCL Pin 5
GND Pin 6

If you are not connecting an external 5 V supply, also connect the 5 V (Pin 2) from your host. This makes IO Zero 32 compatible with Arduino-class boards and any SBC that exposes I²C on individual breakout pins rather than a 40-pin header, including the Raspberry Pi Pico.

Assembly Instructions

The IO Zero 32 is supplied with the 40-pin GPIO connector unsoldered. Before using the IO Zero 32, you need to solder the connector onto the PCB. The power link and I2C address selection are configured using solder jumpers. For 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, press the 40-pin connector down onto the Raspberry Pi GPIO pins with the board sitting over the top of the Raspberry Pi.

If you are installing more than one IO Zero 32 on a single Raspberry Pi board, 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.

Assembly Guide Video

Watch our assembly guide on YouTube. (opens in a new window)

PCB Header Assembly Jig

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

Use

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 places. The I2C address table shows the recommended configurations for your IO Zero 32 and the associated I2C addresses.

Note:
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 connect a pin to Vcc (high).

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

I2C Address Table

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

Code Libraries and Tutorials

All AB Electronics software libraries are open-source and available on our GitHub repository. Libraries are available for the following languages and frameworks, covering Raspberry Pi, Orange Pi, Asus Tinker Board, Odroid, and other Linux-based SBCs with I²C support:

Language   Notes
Download Python 2 and 3 code samples Python Works on any Linux SBC with the smbus or smbus2 package
Download MicroPython code samples MicroPython For Raspberry Pi Pico and other MicroPython-capable microcontrollers
Node js code samples Node.js Suitable for server-side or IoT automation on Linux SBCs
C code samples C Bare-metal performance on any I²C-capable Linux board
C++ code samples C++ Bare-metal performance with object-orientation on any I²C-capable Linux board

See the IO Zero 32 Knowledge Base for platform-specific setup guides, including I²C configuration walkthroughs for Orange Pi, Asus Tinker Board, and Odroid.

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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 abelectronics.co.uk 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.

Shipping and Delivery

For orders under £35 and tracked orders, the following delivery charges apply.

Shipping Rates

United Kingdom

Service Cost Estimated Delivery Time
Royal Mail 1st Class £3.29 1 - 3 days (Mon - Sat)
Royal Mail Special Delivery (Tracked) £8.49 Next day (Mon - Sat)

European Union

Deliveries to: Austria, Belgium, Bulgaria, Croatia, Republic of Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain and Sweden.

Service Cost Estimated Delivery Time
Royal Mail Airmail Service £4.29 3-5 Working Days **
Royal Mail International Tracked and Signed £12.99 3-5 Working Days **

Rest of the World

Service Cost Estimated Delivery Time
Royal Mail Airmail Service £5.99 5-7 Working Days **
Royal Mail International Tracked and Signed £18.99 5-7 Working Days **

 

Free delivery uses the Royal Mail 1st Class service for UK orders and Royal Mail Airmail Service for international orders.

** All International destinations are subject to customs clearance at the destination country, which can add a short delay to your delivery times. Additional import duty may be charged for your order by customs on arrival to your country based on the order value.

We have a full list of all available delivery destinations on the Shipping Country List.

We aim to dispatch your order within 1 working day.

Working days are normal weekdays; dispatch times do not include Saturdays, Sundays and national holidays. Delivery transit times do not include national holidays and Sundays but may include Saturdays, depending on the delivery service provider in the destination country.

You can view details of international shipping issues and delays with the Royal Mail airmail service at Royal Mail International Incident Bulletin.

You can check the status of your order by going to the My Account area of the website.

EU Orders: VAT & Customs Duty

Orders of €150 or less (most orders)

We collect VAT and customs charges at checkout, so there are no surprise fees when your parcel arrives.

  • VAT is included in your checkout price under our IOSS registration.
  • From 1 July 2026, Council Regulation (EU) 2026/382 adds a flat customs duty of €3 per HS tariff code. Most orders use a single HS code, so this is usually a one-off €3 charge.
  • A postal handling fee is added to shipping: Ireland £0.50, rest of EU £1.00, Switzerland £4.00, Norway £8.00.
  • Nothing further to pay on delivery.

Orders over €150

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  • Use Guest Checkout and enter your VAT number to reclaim VAT (not available via PayPal Express).

Questions about a specific order? Contact us.

Order Tracking

Our standard shipping service is not tracked, and we cannot supply tracking information for your order.

We can offer alternative shipping using Royal Mail, tracked and signed for service. You can select this option at checkout. Please note full end-to-end tracking depends on the tracking service from the regional postal service in the destination country.

Once your order has been sent, you can view your tracking code, which is available in the My Account section. Please allow up to 72 hours for your tracking code to be added to your order after despatch.

Returns, refunds and your right to withdraw

Two things apply to your order: your statutory rights as a consumer, and our 180-day returns guarantee on top of them. We never use the guarantee to reduce your legal rights. Where the law gives you more, the law applies.

Your right to withdraw (consumers)

If you bought from us as a consumer, you have 14 days to change your mind for any reason, without needing to keep the item sealed.

The 14 days run from the day you, or someone you nominate, received the goods. Where an order arrives in separate deliveries, the period runs from the day you received the last item.

To withdraw, use our withdrawal function, labelled "Withdraw from contract here", in the My Account area under your order. If you checked out as a guest, use the link in your order confirmation email and verify your order number and email address. You can also tell us in any other clear statement, such as an email. Either way, we'll send you a timestamped acknowledgement by email.

You may open and inspect a board to check it works, as you would in a shop, and still withdraw. You don't have to keep it unopened to exercise this right. You may be liable for any reduction in the item's value caused by handling beyond what's needed to establish how it works.

Once you withdraw, we refund the price you paid plus the standard outbound delivery cost, within 14 days. We may hold the refund until we've received the goods back, or until you show proof you've sent them. You're responsible for the cost of returning the items, and the parcel is your responsibility until it reaches us, so we recommend a tracked or insured service.

Some items are excluded from the statutory right to withdraw, for example goods made or configured to your specification. We'll make this clear before you order where it applies.

Faulty items

Separately from the right to withdraw, if a board is faulty or not as described, your statutory rights apply. Consumers in the EU have a legal guarantee of two years from delivery. All Raspberry Pi add-on boards are tested during production, and all inputs and outputs are checked to ensure they are within the specified ratings. We cannot accept returns for faults caused by over-voltage applied to the inputs by the purchaser, as this is damage rather than a fault.

Our 180-day returns guarantee

In addition to your statutory rights, if for any reason you are unhappy with your purchase you may return it within 180 days of the date you received it, in its original condition and unopened, with any seals and shrink-wrap intact, and we will issue a full refund for the price you paid. This guarantee is our own, beyond what the law requires, which is why it asks for items to be unopened. Opened items can only be accepted under this guarantee if they are faulty.

When returning an item, please state why you are returning it and whether you want a refund or an exchange.

Business customers

The right to withdraw applies to consumers. Orders placed in the course of a business, including boards bought as components for incorporation into other products, are not covered by the consumer right to withdraw. Our 180-day guarantee still applies as set out above.

Refunds

The time a refund takes to reach you depends on the banks involved, but it would normally take 3 to 5 working days to complete once issued.

Your statutory rights

Nothing in this policy affects or limits your statutory rights. Where our terms are more generous than the law requires, the more generous terms apply; where the law gives you more, the law applies. Customers in the United Kingdom have an equivalent 14-day cancellation right under the Consumer Contracts Regulations 2013.

Removed Delivery Destinations

We regret that we had to remove the following countries from our delivery destinations due to a very high failure rate of our parcels being delivered using the Royal Mail airmail service. This resulted in us refunding all of the missing orders, and we cannot continue to make such large losses by sending parcels to destinations where a large percentage of the items are lost in the postal systems.

Brazil, China, Israel, Mexico, Saudi Arabia, Singapore, Sri Lanka, Taiwan, Turkey and the United Arab Emirates.

Also, due to problems with the courier delivering parcels to these destinations, we cannot use a third-party courier service for these delivery destinations due to the extra costs involved.

Customers can purchase our products from one of our international resellers.