The Cambridge Boffin: Raspberry Pi GPIO Buffer Project

Raspberry Pi GPIO Buffer Circuit

The Cambridge Boffin Raspberry Pi GPIO Buffer Project is a bi-directional buffer circuit consisting of two octal buffer integrated circuits, providing eight I/O lines with LEDs. The purpose of this project is to make electronics and computing affordable to the widest range of people. It utilises the least cost components currently found, and is completely open source allowing the use of alternative components.

One of the problems with using just a single set of components is that very soon the suppliers starts hiking-up the prices when they notice a demand, however if students are aware that alternative components could be used, then they have a wider choice, and the competition between suppliers has the effect of lowering the prices. That is theory from the economics school of Peter Vis.

If you cannot afford to buy the Gertboard -- which is a fantastic product worth getting -- and all you need are some bi-directional buffers, then this project might help, however it does involve understanding how octal buffer chips work, and how the pins are arranged. If you take the time to understand how buffer chips work, then this knowledge will serve you well for the future and keep you in good stead... At the very worst, you too could become a Chief Technology Director of a large multinational firm. :-)

I have decided to give all of my electronic projects whimsical names. I chose “Cambridge Boffin” because I love the town of Cambridge and I often speak with many boffins when I visit my professor friends to work on abstract mathematical theories. They pay me in boxes of toffee fudge, which is just enough to last me a whole year.

I believe toffee fudge should be the new currency during inflation periods. Based on sound economic theory -- and what I understood by listening to Mervyn King on television -- I figure two boxes per pound is the best exchange rate going, and far better than the Euro could offer. When you visit Cambridge, be sure to sample the toffee fudge from their local shops. If you can afford to buy any of the components for this project from their local shops then you should do so as it keeps the local economy going.

My grading system is very simple; all the grades are an instant pass and an instant first class degree :-) No need for your parents to send a wheelbarrow full of money either, instead they can donate through the charity link if they wish.

If you do the entry-level Boffin project, which involves wiring up a buffer chip, and understanding how it works, then this is a good basic grade. However as you can see there are Boffin A+ and Boffin A++ grades to strive for.

I will be adding content for these extra grades depending upon the demand or if I can spare some time. When this happens all the previous grades will be devalued of course -- just a little party-political trick I learnt from our governments over the years. :-)

Note: This is just an abstract virtual grading system please do not contact me for a certificate, you have to honestly grade yourself based on how well you think you did. You can of course take a photograph of your completed board and show it to everyone on the Raspberry Pi forums. Be sure to provide a link to this article so that other people know how to build one.

If you are a student and you need small quantities of components cheaply, the only place I was able to find cheap was eBay. You can buy things by the dozen for a few pounds including postage, and there is no minimum order value, which is even better. Unfortunately, it tends to come from the Far East such as China, and Singapore and can take up to two weeks for delivery, but well worth the wait if you are able to plan.

For the solder, I am using a special solder called Omega, which is much safer for school and college environments, where students might be suffering asthma related “wheeziness” due to soldering.


For this project, I am using a prototyping board, which is 18 holes × 24 holes in size and used for testing out circuit ideas. Although it appears large, remember that it is 5 cm × 7 cm in size, which is roughly the same size as a credit card. You can pack quite a lot of components on this little board if you plan the layout properly. I managed to get ten prototyping boards for £1.20 including postage! That is good value, and just affordable for students in this inflation climate.

For more information on how to use these boards, the best soldering iron to use, and solder please refer to the article called PCB Prototype Matrix Board 50 mm × 70 mm. You could buy a hundred of these boards for just £12 to cover for a whole class. These neat little boards are very handy for small electronic circuits and experiments.

A very low power (15 W) soldering iron works well with the boards, anything more powerful might very likely char the boards, and the soldering will not be very shiny either. It is also easier to join the pads together with solder when using a low wattage soldering iron.

This project is for the younger adults who are responsible and capable of using a low wattage soldering iron unsupervised. Do not use a soldering iron if you are under the age of 18 and are unsupervised.

This Article Continues...

The Cambridge Boffin: Raspberry Pi GPIO Buffer Project
The Boffin Proficiency Grade: Raspberry Pi GPIO Buffer Circuit
Boffin A+ Grade: Raspberry Pi GPIO Buffer Circuit
Boffin A++ Grade: Raspberry Pi GPIO Buffer Circuit
Raspberry Pi GPIO Buffer Circuit: Jumper Configuration
Reference: SN74HC244N Pinout & Principle