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IO Pi Zero

Legacy product information for the IO Pi Zero
Created: 23/04/2022 | Last Updated: 23/04/2022

This item has been replaced with the IO Zero 32.

Link to go here

Features

  • 16 Digital Inputs/Outputs
  • Control via the Raspberry Pi I2C port
  • Stack up to 8 IO Pi boards on a single Raspberry Pi
  • Solder pad selectable I2C addresses
  • External 5V Input with isolation pad
  • 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

The IO Pi Zero is a 16 channel digital expansion board designed for use on the Raspberry Pi Zero. The board is based around the MCP23017 16-bit I/O expander from Microchip Technology Inc. A MCP23017 expander is included on the board allowing you to connect up to 16 digital inputs or outputs to the Raspberry Pi.  The IO Pi Zero 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 Zero along with other expansion boards.

The I2C address bits are selectable using the on-board jumpers. The MCP23017 supports up to 8 different I2C addresses so with one MCP23017 device on each IO Pi Zero you can stack up to 8 IO Pi Zero boards on a single Raspberry Pi giving a maximum of 128 I/O ports.

The IO Pi Zero 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 to your Raspberry Pi.

To use the IO Pi Zero 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 Pi Zero.  The 5V pin will also need to be connected if you are not using an external 5V power supply.

Input Ratings & Specifications

Spec
Ratings
Vdd (5V pin on I2C bus)
2.7V - 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

3D CAD Model

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

Schematic

Click to download
Click to download schematic PDF.

Mechanical Drawings

Mechanical Drawing

Click image to enlarge

The IO Pi Zero is supplied with the 40 pin GPIO connector unsoldered.

We supply the IO Pi Zero this way because the Raspberry Pi Zero is also supplied without a GPIO header and the IO Pi Zero could therefore be fitted both above or below the Raspberry Pi Zero.

Before using the IO Pi Zero you will need to solder the 40 pin GPIO connectors onto the PCB.  

 

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 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 Zero 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 Pi Zero 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)

I2C Address Table

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

We have Python, 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,

Microchip MCP23017

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