IO Zero 32

32 channel digital I/O development board for the Raspberry Pi

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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

We have tested the IO Zero 32 on the following platforms.

Model Status
Raspberry Pi Pico series
Raspberry Pi Model A / B
Raspberry Pi 1 Model A+ / B+
Raspberry Pi 2 Model B
Raspberry Pi 3 Model A+ / B / B+
Raspberry Pi 4 Model B
Raspberry Pi 5
Raspberry Pi Zero
Raspberry Pi Zero W / Zero 2 W
Raspberry Pi Compute Module 4 IO Board
Raspberry Pi 400
Orange Pi
Asus Tinker Board
Odroid

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

We have Python, MicroPython, C, C++, Node.js and .Net Core libraries for this expansion board.  All of our software libraries are open source and can be download from our GitHub repository or by clicking on the logos below for your selected programming language.

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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 £2.49 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.

Import One-Stop Shop (IOSS) FAQ

What is the Import One-Stop Shop (IOSS)?

The Import One-Stop Shop (IOSS) is a system introduced by the European Union to simplify VAT collection for goods valued at €150 or less that are shipped to customers in the EU from outside the EU. By using IOSS, sellers collect VAT at the point of sale, ensuring that buyers do not have to pay additional import taxes or customs fees upon delivery.

How does IOSS benefit me as a customer?

IOSS makes your shopping experience easier and more transparent by:

Including VAT in the purchase price you see at checkout.

Eliminating unexpected customs charges or fees upon delivery.

Reducing potential delivery delays caused by customs clearance.

Will I have to pay any additional charges when my order is delivered?

No. If your order is covered by IOSS, all applicable VAT and import charges are already included in the price you pay at checkout. There will be no additional charges when your order is delivered.

How do I know if my order is covered by IOSS?

All orders shipped to EU countries and valued at €150 or less are covered by our IOSS registration. If your order qualifies, the VAT and import fees will be automatically calculated and included in the total price during checkout.

Does IOSS apply to all products?

IOSS applies to goods valued at €150 or less that are shipped from outside the EU to customers in EU member states. Certain items, such as excisable goods (e.g., alcohol or tobacco), may not qualify for IOSS coverage.

What happens if my order exceeds €150?

For orders valued above €150, IOSS does not apply. In such cases, import VAT and any applicable customs duties will need to be paid separately, usually upon delivery. We recommend checking your local regulations for further details.

Do I need to do anything to use IOSS?

No action is required on your part. We handle all the necessary IOSS processes on our end to ensure your order is VAT-compliant and free from additional import fees.

Does IOSS reduce delivery times?

Yes, IOSS can help speed up delivery times by streamlining the customs clearance process. Since VAT is prepaid, your order is less likely to be delayed during customs inspections.

Is IOSS available in all EU countries?

Yes, IOSS applies to all EU member states. Regardless of where you are in the EU, you can enjoy the benefits of IOSS when shopping with us.

Can I claim VAT back if I am VAT registered in the EU?

If you are VAT registered in the EU and wish to claim VAT back, please use the Guest Checkout and enter your VAT registration details before placing your order. It is not possible to enter your VAT details when using the PayPal express checkout.

What should I do if I still have questions?

If you have any further questions about IOSS or your order, feel free to contact our customer support team. We’re here to help!

Delivery Duty Unpaid for orders sent outside of the United Kingdom and EU over 150 euros

All orders sent to countries other than the United Kingdom and EU over 150 euros are shipped on a DDU (Delivery Duty Unpaid) basis, and the recipient may be subject to local taxes and customs import duty, which is charged on the value of the order.

Payment of these fees is the sole responsibility of the customer. 

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

Our 180-day returns guarantee means that if for any reason you are unhappy with your purchase, you may return it to us in its original condition within 180 days of the date you received the item, unopened (with any seals and shrink-wrap intact), and we will issue a full refund for the price you paid for the item. We can only accept the return of opened items if they are faulty.

All Raspberry Pi add-on boards are checked on a Raspberry Pi during production, and all inputs are checked to ensure the inputs and outputs are within the specified ratings.

We cannot accept returns for faults caused by over-voltage being applied to inputs on the boards by the purchaser.

When returning an item to us, please clearly state why you are returning your parcel and whether you require a refund or exchange. Please note that the parcel is your responsibility until it reaches us, so we recommend you send it via registered or recorded post. 

The time it takes for a refund to reach the customer depends on the banks involved. It would normally take 3 - 5 working days to complete it.

Sales Tax

United Kingdom VAT at 20% is added to all orders for UK destinations. VAT is not added to NON-UK and EU destinations where the order total is more than 150 euros.

We are not responsible for any import taxes or VAT on the orders in the destination country. Import duty/tax is always paid by the person/company receiving the parcel/order.

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, USA (due to shipping tariffs)  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

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