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Slice of PI/O

£5.96 (inc VAT) £4.97 (exc VAT)

Stop:  All of our products are now only available at wirelessthings.net, this is also the new home for our new products and documentation. 

This product is available here.


Product description

The Slice of Pi/O gives a Raspberry Pi an extra 16 buffered inputs or outputs. There's now quite a few people making boards with the MCP23017 driver chip on so there's lots of code examples about. We think our baord represents some great lateral thinking and superb design. The main features are:

  •  Buffered output/input (protects your PI from miswires, shorts, overload and general abuse)
  • Construction is very easy (suitable even for children with basic soldering skills)
  • Supports 3.3v and 5v operation (selectable by jumper)
  • Can be powered externally also (for when your project needs more than the Pi can provide, remove red jumper and wire to pad "EXT POWER")
  • SPI and I2C pins to standard 2.54mm pitch holes (fast and easy access)
  • GPIO pins to standard 2.54mm pitch holes (fast and easy access)
  • Daisy chainable to 128 ports! (for when you need more than just 16 I/O's)
  • 4 wire daisy chain connector (PWR/GND/SCL/SDA)
  • I2C address selectable (means you can run more than a single I2C board)
  • Featured in popular publications (good base of knowledge around the board)
  • Available worldwide (many people now stock the board)


  • Gold plated finish (Protection against oxidization means your device will outlast normal solder finish boards)
  • Comes as a complete "self solder" kit of parts
  • IC chip has decoupling capacitors to minimise noise
  • Upto 200ma at 5v can be drawn by the Pi
  • Upto 50ma at 3.3v can be drawn by the Pi
  • Pads for the MCP interupt pins
  • IC chip is socketed to allow for replacement if needed
  • Made in the UK

Technical data

Dimensions: 35.5mm x 51.5mm x 18.9mm


There is currently no downloads for the product.


Instant get started guide

Build guide





Related or associated products

The Slice of PI - http://shop.ciseco.co.uk/slice-of-pi-add-on-for-raspberry-pi/

Also available from

UK - Maplin Electronics - ModMyPi - Rapid Electronics

Really important note from us

Make an informed purchase

We strongly recommend you read all about this item before purchase. Our products are intended for people who love the challenge of being part of making things. Some items are easy to use and some are not, please make your decision to buy based on what you see combined with your own experience levels. Please don't rush in, if you need to ask questions, please do on our forum at Openmicros.org


We offer various choices of postage, please be aware the lowest cost options are usually not tracked. If your order has not been received within a reasonable time please follow this link

Write your own product review

  1. Great add-on - much safer experimenting 4 Star Review

    Posted by on 20th Oct 2012

    As a board, reasonably easy to assemble (even with my inexpert soldering skills). Opens up lots of options for safer experimentation than connecting things up to the PI directly.

    To improve, maybe repeat some of the MCP23017 info in a more Slice of PI/O specific way to help people get started using it, e.g. adding a few LEDs for testing and including some more info on things like the power jumper.


  2. This is one of my favourite little boards 5 Star Review

    Posted by on 13th Sep 2012

    A great add-on for the Pi. Very easy to assemble and perfect for expanding the GPIO abilities of the Pi from the standard header.

    Providing you check which version of the Pi you are using and therefore select the correct channel you should be good to go.

    How could it improve? Well, it would be good to include some additional header pins for the daisy chaining element, and watch out for the incorrect labelling of B0-B7 as they are the wrong way round. i.e. B0 is actually B7 etc. It took me a couple of days of head scratching before I went back to basics to look closely at the tracks to see where they went. At this price it's worth having a few of them at hand.

    There's a note in the build doc about the miss labeled pins and this will be corrected in the next batch of boards.

  3. Slice Of Pi I/O 4 Star Review

    Posted by on 13th Sep 2012

    Nice Kit. My only grip is that the hole by the free end of the board is in a bad place. Half over a very very tiny component, C12 on the Pi, so if a nylon screw (not supplied) is used as a pillar to stop the board shorting on the can by RG2 then it could easily damage C12.

  4. Great board but documentation should be provided 5 Star Review

    Posted by on 9th Sep 2012

    Easy to construct and components nicely laid out. Potential gotcha for Pi Revision 2 users, they have swapped the I2C channels so the I2CDetect command as shown won't show the board, you need to change the zero to a one in the command I.e. i2cdetect -y 1. Wasted some time re-checking all my soldering before remembering reading something on the pi blog.

    UPDATE: Documentation is here http://openmicros.org/index.php/articles/94-ciseco-product-documentation/raspberry-pi/223-slice-of-pio

  5. Request for pinout information 4 Star Review

    Posted by on 23rd Aug 2012

    I am a complete novice and have built my Slice of PI/O board as shown. I have soldered the three pins to give me an address of 0x20 and this works fine.
    I have three questions that I hope someone will answer:
    (i) Nathan says of his board
    "Note: Make sure pins 15,16,17 of the MCP23017 all connected to ground (the 3 pins top left of the diagram, shown linked in blue).
    Is this still necessary, or does this board prevent the problem?

    (ii) Am I correct in thinking the pinouts on the PI/O labelled A0 to A7, and B0 to B7, each have their own ground pin beside them?

    (iii) Which of the pins on the board equates to the 5v and GND on the Pi?

    Thanks in advance for your help.

    CISECO : Hi you didnt say who you were, would you either put a question on the forum or reply to your shop/ebay order.

  6. Documentation hard to find 4 Star Review

    Posted by on 17th Aug 2012

    The product page should contain a link to the construction details:


    The "4 wire daisy chain connector (PWR/GND/SCL/SDA)" is not explicitly identified. It should contain at least one additional wire, for connection to interrupt pins on downstream boards. It is not really difficult to identify the 4 pins, but it should not be necessary. There should be an illustration of the recommended connection.

    Because the 26-pin connector to the Raspberry Pi can be installed in two orientations, there should be identification of the pin 1 location. The product image shows clearly the board should be positioned over the top of the Raspberry Pi, but with two ways to connect it, I can imagine it will sometimes be plugged incorrectly.

    It looks like the circuitry beneath the Slice of PI/O might contact the metal can labeled C6 on the Raspberry Pi (the RPi sechmatic suggests this might actually be C3). There is normally some clearance at this point, but the assembly is not rigid and might flex enough to short when a connection is made, particularly to a bank B pin. Some insulation on the top of this can, or on the bottom of the PI/O board, should prevent a short.

    Finally, the GP0 ... GP7 labels are inconvenient. It would be better to use the Broadcom GPIO pin numbers, because that is what a program typically needs to use to control these pins. At the very least, document which pin on the 26-pin RPi connector is routed to GP0, GP1, etc. I can use an ohmmeter, but it ought not to be necessary.

    Despite this, it is a neat little device, at a very reasonable price.

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