The Howff 3D scanning rig| The MagPi 99

How do you create a 3D model of a historic graveyard? With eight Raspberry Pi computers, as Rob Zwetsloot discovers in the latest issue of The MagPi magazine, out now.

The software builds up the 3D model of the graveyard

“In the city centre of Dundee is a historical burial ground, The Howff,” says Daniel Muirhead. We should probably clarify that he’s a 3D artist. “This old graveyard is densely packed with around 1500 gravestones and other funerary monuments, which happens to make it an excellent technical challenge for photogrammetry photo capture.”

This architecture, stone paths, and vibrant flora is why Daniel ended up creating a 3D-scanning rig out of eight Raspberry Pi computers. And the results are quite stunning.

Eight Raspberry Pi computers are mounted to the ball, with cameras pointing towards the ground

“The goal of this project was to capture photos for use in generating a 3D model of the ground,” he continues. “That model will be used as a base for attaching individual gravestone models and eventually building up a full composite model of this complex subject. The ground model will also be purposed for rendering an ultra-high-resolution map of the graveyard. The historical graveyard has a very active community group that are engaged in its study and digitisation, the Dundee Howff Conservation Group, so I will be sharing my digital outputs with them.”

Google graveyard

There are thousands of pictures, like this one, being used to create the model

To move the rig throughout the graveyard, Daniel used himself as the major moving part. With the eight Raspberry Pi cameras taking a photo every two seconds, he was able to capture over 180,000 photos over 13 hours of capture sessions.

“The rig was held above my head and the cameras were angled in such a way as to occlude me from view, so I was not captured in the photographs which instead were focused on the ground,” he explains. “Of the eight cameras, four were the regular model with 53.5 ° horizontal field of view (FoV), and the other four were a wide-angle model with 120 ° FoV. These were arranged on the rig pointing outwards in eight different directions, alternating regular and wide-angle, all angled at a similar pitch down towards the ground. During capture, the rig was rotated by +45 ° for every second position, so that the wide-angles were facing where the regulars had been facing on the previous capture, and vice versa.”
Daniel worked according to a very specific grid pattern, staying in one spot for five seconds at a time, with the hopes that at the end he’d have every patch of ground photographed from 16 different positions and angles.

Maker Daniel Muirhead is a 3D artist with an interest in historical architecture

“With a lot of photo data to scan through for something fairly complex, we wondered how well the system had worked. Daniel tells us the only problems he had were with some bug fixing on his code: “The images were separated into batches of around 10,000 (1250 photos from each of the eight cameras), plugged into the photogrammetry software, and the software had no problem in reconstructing the ground as a 3D model.”

Accessible 3D surveying

He’s now working towards making it accessible and low-cost to others that might want it. “Low-cost in the triple sense of financial, labour, and time,” he clarifies. “I have logged around 8000 hours in a variety of photogrammetry softwares, in the process capturing over 300,000 photos with a regular camera for use in such files, so I have some experience in this area.”

“With the current state of technology, it should be possible with around £1000 in equipment to perform a terrestrial photo-survey of a town centre in under an hour, then with a combined total of maybe three hours’ manual processing and 20 hours’ automated computer processing, generate a high-quality 3D model, the total production time being under 24 hours. It should be entirely plausible for a local community group to use such a method to perform weekly (or at least monthly) 3D snapshots of their town centre.”

The MagPi issue 99 – Out now

The MagPi magazine is out now, available in print from the Raspberry Pi Press onlinestore, your local newsagents, and the Raspberry Pi Store, Cambridge.

You can also download the PDF directly from the MagPi magazine website.

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YouTuber Jeff Geerling reviews Raspberry Pi Compute Module 4

We love seeing how quickly our community of makers responds when we drop a new product, and one of the fastest off the starting block when we released the new Raspberry Pi Compute Module 4 on Monday was YouTuber Jeff Geerling.

Jeff Geerling

We made him keep it a secret until launch day after we snuck one to him early so we could see what one of YouTube’s chief advocates for our Compute Module line thought of our newest baby.

So how does our newest board compare to its predecessor, Compute Module 3+? In Jeff’s first video (above) he reviews some of Compute Module 4’s new features, and he has gone into tons more detail in this blog post.

Jeff also took to live stream for a Q&A (above) covering some of the most asked questions about Compute Module 4, and sharing some more features he missed in his initial review video.

His next video (above) is pretty cool. Jeff explains:

“Everyone knows you can overclock the Pi 4. But what happens when you overclock a Compute Module 4? The results surprised me!”

Jeff Geerling

And again, there’s tons more detail on temperature measurement, storage performance, and more on Jeff’s blog.

Top job, Jeff. We have our eyes on your channel for more videos on Compute Module 4, coming soon.

If you like what you see on his YouTube channel, you can also sponsor Jeff on GitHub, or support his work via Patreon.

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Digital making projects about protecting our planet

Explore our new free pathway of environmental digital making projects for young people! These new step-by-step projects teach learners Scratch coding and include real-world data — from data about the impact of deforestation on wildlife to sea turtle tracking information.

By following along with the digital making projects online, young people will discover how they can use technology to protect our planet, all while improving their computing skills.

Photo of a young woman holding an origami bird up to the camera
One of the new projects is an automatic creature counter based on colour recognition with Scratch

The projects help young people affect change

In the projects, learners are introduced to 5 of the United Nations’ 17 Sustainable Development Goals (SDGs) with an environment focus:

  • Affordable and Clean Energy
  • Responsible Consumption and Production
  • Climate Action
  • Life Below Water
  • Life on Land
Screenshot of a Scratch project showing a panda and the Earth
The first project in the new pathway is an animation about the UN’s five SDGs focused on the environment.

Technology, science, maths, geography, and design all play a part in the projects. Following along with the digital making projects, young people learn coding and computing skills while drawing on a range of data from across the world. In this way they will discover how computing can be harnessed to collect environmental data, to explore causes of environmental degradation, to see how humans influence the environment, and ultimately to mitigate negative effects.

Where does the real-world data come from?

To help us develop these environmental digital making projects, we reached out to a number of organisations with green credentials:

Green Sea Turtle Alasdair Davies Raspberry Pi
A sea turtle is being tagged so its movements can be tracked

Inspiring young people about coding with real-world data

The digital making projects, created with 9- to 11-year-old learners in mind, support young people on a step-by-step pathway to develop their skills gradually. Using the block-based visual programming language Scratch, learners build on programming foundations such as sequencing, loops, variables, and selection. The project pathway is designed so that learners can apply what they learned in earlier projects when following along with later projects!

The final project in the pathway, ‘Turtle tracker’, uses real-world data of migrating sea turtles!

We’re really excited to help learners explore the relationship between technology and the environment with these new digital making projects. Connecting their learning to real-world scenarios not only allows young people to build their knowledge of computing, but also gives them the opportunity to affect change and make a difference to their world!

Discover the new digital making projects yourself!

With Green goals, learners create an animation to present the United Nations’ environment-focused Sustainable Development Goals.

Through Save the shark, young people explore sharks’ favourite food source (fish, not humans!), as well as the impact of plastic in the sea, which harms sharks in their natural ocean habitat.

Illustration of a shark with sunglasses

With the Tree life simulator project guide, learners create a project that shows the impact of land management and deforestation on trees, wildlife, and the environment.

Computers can be used to study wildlife in areas where it’s not practical to do so in person. In Count the creatures, learners create a wildlife camera using their computer’s camera and Scratch’s new video sensing extension!

Electricity is important. After all, it powers the computer that learners are using! In Electricity generation, learners input real data about the type and amount of natural resources countries across the world use to generate electricity, and they then compare the results using an animated data visualisation.

Understanding the movements of endangered turtles helps to protect these wonderful animals. In this new Turtle tracker project, learners use tracking data from real-life turtles to map their movements off the coast of West Africa.

Code along wherever you are!

All of our projects are free to access online at any time and include step-by-step instructions. They can be undertaken in a club, classroom, or at home. Young people can share the project they create with their peers, friends, family, and the wider Scratch community.

Visit the Protect our planet pathway to experience the projects yourself.

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Talk to your Raspberry Pi | HackSpace 36

In the latest issue of HackSpace Magazine, out now, @MrPJEvans shows you how to add voice commands to your projects with a Raspberry Pi 4 and a microphone.

You’ll need:

It’s amazing how we’ve come from everything being keyboard-based to so much voice control in our lives. Siri, Alexa, and Cortana are everywhere and happy to answer questions, play you music, or help automate your household.

For the keen maker, these offerings may not be ideal for augmenting their latest project as they are closed systems. The good news is, with a bit of help from Google, you can add voice recognition to your project and have complete control over what happens. You just need a Raspberry Pi 4, a speaker array, and a Google account to get started.

Set up your microphone

This clever speaker uses four microphones working together to increase accuracy. A ring of twelve RGB LEDs can be coded to react to events, just like an Amazon Echo

For a home assistant device, being able to hear you clearly is an essential. Many microphones are either too low-quality for the task, or are unidirectional: they only hear well in one direction. To the rescue comes Seeed’s ReSpeaker, an array of four microphones with some clever digital processing to provide the kind of listening capability normally found on an Amazon Echo device or Google Assistant. It’s also in a convenient HAT form factor, and comes with a ring of twelve RGB LEDs, so you can add visual effects too. Start with a Raspberry Pi OS Lite installation, and follow these instructions to get your ReSpeaker ready for use.

Install Snowboy

You’ll see later on that we can add the power of Google’s speech-to-text API by streaming audio over the internet. However, we don’t want to be doing that all the time. Snowboy is an offline ‘hotword’ detector. We can have Snowboy running all the time, and when your choice of word is ‘heard’, we switch to Google’s system for accurate processing. Snowboy can only handle a few words, so we only use it for the ‘trigger’ words. It’s not the friendliest of installations so, to get you up and running, we’ve provided step-by-step instructions.

There’s also a two-microphone ReSpeaker for the Raspberry Pi Zero

Create your own hotword

As we’ve just mentioned, we can have a hotword (or trigger word) to activate full speech recognition so we can stay offline. To do this, Snowboy must be trained to understand the word chosen. The code that describes the word (and specifically your pronunciation of it) is called the model. Luckily, this whole process is handled for you at snowboy.kitt.ai, where you can create a model file in a matter of minutes and download it. Just say your choice of words three times, and you’re done. Transfer the model to your Raspberry Pi 4 and place it in your home directory.

Let’s go Google

ReSpeaker can use its multiple mics to detect distance and direction

After the trigger word is heard, we want Google’s fleet of super-servers to help us transcribe what is being said. To use Google’s speech-to-text API, you will need to create a Google application and give it permissions to use the API. When you create the application, you will be given the opportunity to download ‘credentials’ (a small text file) which will allow your setup to use the Google API. Please note that you will need a billable account for this, although you get one hour of free speech-to-text per month. Full instructions on how to get set up can be found here.

Install the SDK and transcriber

To use Google’s API, we need to install the firm’s speech-to-text SDK for Python so we can stream audio and get the results. On the command line, run the following:pip3 install google-cloud-speech<br/>(If you get an error, run sudo apt install python3-pip then try again).
Remember that credentials file? We need to tell the SDK where it is:
export GOOGLE_APPLICATION_CREDENTIALS="/home/pi/[FILE_NAME].json"<br/>(Don’t forget to replace [FILE_NAME] with the actual name of the JSON file.)
Now download and run this test file. Try saying something and see what happens!

Putting it all together

Now we can talk to our Raspberry Pi, it’s time to link the hotword system to the Google transcription service to create our very own virtual assistant. We’ve provided sample code so that you can see these two systems running together. Run it, then say your chosen hotword. Now ask ‘what time is it?’ to get a response. (Don’t forget to connect a speaker to the audio output if you’re not using HDMI.) Now it’s over to you. Try adding code to respond to certain commands such as ‘turn the light on’, or ‘what time is it?’

Get HackSpace magazine 36 Out Now!

Each month, HackSpace magazine brings you the best projects, tips, tricks and tutorials from the makersphere. You can get it from the Raspberry Pi Press online store, The Raspberry Pi store in Cambridge, or your local newsagents.

Each issue is free to download from the HackSpace magazine website.

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Take part in the PA Raspberry Pi Competition for UK schools

Every year, we support the PA Raspberry Pi Competition for UK schools, run by PA Consulting. In this free competition, teams of students from schools all over the UK imagine, design, and create Raspberry Pi–powered inventions.

Female engineer with Raspberry Pi device. Copyright © University of Southampton
Let’s inspire young people to take up a career in STEM!
© University of Southampton

The PA Raspberry Pi Competition aims to inspire young people aged 8 to 18 to learn STEM skills, teamwork, and creativity, and to move toward a career in STEM.

We invite all UK teachers to register if you have students at your school who would love to take part!

For the first 100 teams to complete registration and submit their entry form, PA Consulting provides a free Raspberry Pi Starter Kit to create their invention.

This year’s competition theme: Innovating for a better world

The theme is deliberately broad so that teams can show off their creativity and ingenuity.

  • All learners aged 8 to 18 can take part, and projects are judged in four age groups
  • The judging categories include team passion; simplicity and clarity of build instructions; world benefit; and commercial potential
  • The proposed budget for a team’s invention is around £100
  • The projects can be part of your students’ coursework
  • Entries must be submitted by Monday 22 March 2021
  • You’ll find more details and inspiration on the PA Raspberry Pi Competition webpage

Among all the entries, judges from the tech sector and the Raspberry Pi Foundation choose the finalists with the most outstanding inventions in their age group.

The Dynamix team, finalists in last round’s Y4–6 group, built a project called SmartRoad+

The final teams get to take part in an exciting awards event to present their creations so that the final winners can be selected. This round’s PA Raspberry Pi Awards Ceremony takes place on Wednesday 28 April 2021, and PA Consulting are currently considering whether this will be a physical or virtual event.

All teams that participate in the competition will be rewarded with certificates, and there’s of course the chance to win trophies and prizes too!

You can prepare with our free online courses

If you would like to boost your skills so you can better support your team, then sign up to one of our free online courses designed for educators:

Take inspiration from the winners of the previous round

All entries are welcome, no matter what your students’ experience is! Here are the outstanding projects from last year’s competition:

A look inside the air quality-monitoring project by Team Tempest, last round’s winners in the Y7–9 group

Find out more at the PA Raspberry Pi Competition webinar!

To support teachers in guiding their teams through the competition, PA Consulting will hold a webinar on 12 November 2020 at 4.30–5.30pm. Sign up to hear first-hand what’s involved in taking part in the PA Raspberry Pi Competition, and use the opportunity to ask questions!

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New book: Create Graphical User Interfaces with Python

Laura Sach and Martin O’Hanlon, who are both Learning Managers at the Raspberry Pi Foundation, have written a brand-new book to help you to get more out of your Python projects.

Cover of the book Create Graphical User Interfaces with Python

In Create Graphical User Interfaces with Python, Laura and Martin show you how to add buttons, boxes, pictures, colours, and more to your Python programs using the guizero library, which is easy to use and accessible for all, no matter your Python skills.

This new 156-page book is suitable for everyone — from beginners to experienced Python programmers — who wants to explore graphical user interfaces (GUIs).

Meet the authors

Screenshot of a Digital Making at Home live stream session
That’s Martin in the blue T-shirt with our Digital Making at Home live stream hosts Matt and Christina

You might have met Martin recently on one of our weekly Digital Making at Home live streams for young people, were he was a guest for an ‘ooey-GUI’ code-along session. He talked about his background and what it’s like creating projects and learning resources on a day-to-day basis.

Laura is also pretty cool! Here she is showing you how to solder your Raspberry Pi header pins:

Hi Laura!

Martin and Laura are also tonnes of fun on Twitter. You can find Martin as @martinohanlon, and Laura goes by @codeboom.

10 fun projects

In Create Graphical User Interfaces with Python, you’ll find ten fun Python projects to create with guizero, including a painting program, an emoji match game, and a stop-motion animation creator.

A double-page from the book Create Graphical User Interfaces with Python
A peek inside Laura’s and Martin’s new book

You will also learn:

  • How to create fun Python games and programs
  • How to code your own graphical user interfaces using windows, text boxes, buttons, images, and more
  • What event-based programming is
  • What good (and bad) user interface design is
A double-page from the book Create Graphical User Interfaces with Python
Ain’t it pretty?

Where can I get it?

You can buy Create Graphical User Interfaces with Python now from the Raspberry Pi Press online store, or the Raspberry Pi store in Cambridge, UK.

And if you don’t need the lovely new book, with its new-book smell, in your hands in real life, you can download a PDF version for free, courtesy of The MagPi magazine.

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Formative assessment in the computer science classroom

In computing education research, considerable focus has been put on the design of teaching materials and learning resources, and investigating how young people learn computing concepts. But there has been less focus on assessment, particularly assessment for learning, which is called formative assessment. As classroom teachers are engaged in assessment activities all the time, it’s pretty strange that researchers in the area of computing and computer science in school have not put a lot of focus on this.

Shuchi Grover

That’s why in our most recent seminar, we were delighted to hear about formative assessment — assessment for learning — from Dr Shuchi Grover, of Looking Glass Ventures and Stanford University in the USA. Shuchi has a long track record of work in the learning sciences (called education research in the UK), and her contribution in the area of computational thinking has been hugely influential and widely drawn on in subsequent research.

Two types of assessment

Assessment is typically divided into two types:

  1. Summative assessment (i.e. assessing what has been learned), which typically takes place through examinations, final coursework, projects, etcetera.
  2. Formative assessment (i.e. assessment for learning), which is not aimed at giving grades and typically takes place through questioning, observation, plenary classroom activities, and dialogue with students.

Through formative assessment, teachers seek to find out where students are at, in order to use that information both to direct their preparation for the next teaching activities and to give students useful feedback to help them progress. Formative assessment can be used to surface misconceptions (or alternate conceptions) and for diagnosis of student difficulties.

Venn diagram of how formative assessment practices intersect with teacher knowledge and skills
Click to enlarge

As Shuchi outlined in her talk, a variety of activities can be used for formative assessment, for example:

  • Self- and peer-assessment activities (commonly used in schools).
  • Different forms of questioning and quizzes to support learning (not graded tests).
  • Rubrics and self-explanations (for assessing projects).

A framework for formative assessment

Shuchi described her own research in this topic, including a framework she has developed for formative assessment. This comprises three pillars:

  1. Assessment design.
  2. Teacher or classroom practice.
  3. The role of the community in furthering assessment practice.
Shuchi Grover's framework for formative assessment
Click to enlarge

Shuchi’s presentation then focused on part of the first pillar in the framework: types of assessments, and particularly types of multiple-choice questions that can be automatically marked or graded using software tools. Tools obviously don’t replace teachers, but they can be really useful for providing timely and short-turnaround feedback for students.

As part of formative assessment, carefully chosen questions can also be used to reveal students’ misconceptions about the subject matter — these are called diagnostic questions. Shuchi discussed how in a classroom setting, teachers can employ this kind of question to help them decide what to focus on in future lessons, and to understand their students’ alternate or different conceptions of a topic. 

Formative assessment of programming skills

The remainder of the seminar focused on the formative assessment of programming skills. There are many ways of assessing developing programming skills (see Shuchi’s slides), including Parsons problems, microworlds, hotspot items, rubrics (for artifacts), and multiple-choice questions. As an MCQ example, in the figure below you can see some snippets of block-based code, which students need to read and work out what the outcome of running the snippets will be. 

Click to enlarge

Questions such as this highlight that it’s important for learners to engage in code comprehension and code reading activities when learning to program. This really underlines the fact that such assessment exercises can be used to support learning just as much as to monitor progress.

Formative assessment: our support for teachers

Interestingly, Shuchi commented that in her experience, teachers in the UK are more used to using code reading activities than US teachers. This may be because code comprehension activities are embedded into the curriculum materials and support for pedagogy, both of which the Raspberry Pi Foundation developed as part of the National Centre for Computing Education in England. We explicitly share approaches to teaching programming that incorporate code reading, for example the PRIMM approach. Moreover, our work in the Raspberry Pi Foundation includes the Isaac Computer Science online learning platform for A level computer science students and teachers, which is centered around different types of questions designed as tools for learning.

All these materials are freely available to teachers wherever they are based.

Further work on formative assessment

Based on her work in US classrooms researching this topic, Shuchi’s call to action for teachers was to pay attention to formative assessment in computer science classrooms and to investigate what useful tools can support them to give feedback to students about their learning. 

Advice from Shuchi Grover on how to embed formative assessment in classroom practice
Click to enlarge

Shuchi is currently involved in an NSF-funded research project called CS Assess to further develop formative assessment in computer science via a community of educators. For further reading, there are two chapters related to formative assessment in computer science classrooms in the recently published book Computer Science in K-12 edited by Shuchi.

There was much to take away from this seminar, and we are really grateful to Shuchi for her input and look forward to hearing more about her developing project.

Join our next seminar

If you missed the seminar, you can find the presentation slides and a recording of the Shuchi’s talk on our seminars page.

In our next seminar on Tuesday 3 November at 17:00–18:30 BST / 12:00–13:30 EDT / 9:00–10:30 PT / 18:00–19:30 CEST, I will be presenting my work on PRIMM, particularly focusing on language and talk in programming lessons. To join, simply sign up with your name and email address.

Once you’ve signed up, we’ll email you the seminar meeting link and instructions for joining. If you attended this past seminar, the link remains the same.

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New Chair and Trustees of the Raspberry Pi Foundation

I am delighted to share the news that we have appointed a new Chair and Trustees of the Raspberry Pi Foundation. Between them, they bring an enormous range of experience and expertise to what is already a fantastic Board of Trustees, and I am really looking forward to working with them.

New Chair of the Board of Trustees: John Lazar 

John Lazar has been appointed as the new Chair of the Board of Trustees. John is a software engineer and business leader who is focused on combining technology and entrepreneurship to generate lasting positive impact.

Formerly the Chairman and CEO of Metaswitch Networks, John is now an angel investor, startup mentor, non-executive chairman and board director, including serving as the Chair of What3Words. He is a Fellow of the Royal Academy of Engineering and played an active role in developing the programme of study for England’s school Computer Science curriculum. John has also spent many years working on tech-related non-profit initiatives in Africa and co-founded Enza Capital, which invests in early-stage African technology companies that solve pressing problems.

John takes over the Chair from David Cleevely, who has reached the end of his two three-year terms as Trustee and Chair of the Foundation. David has made a huge contribution to the Foundation over that time, and we are delighted that he will continue to be involved in our work as one of the founding members of the Supporters Club.

New Trustees: Amali de Alwis, Charles Leadbeater, Dan Labbad

Alongside John, we are welcoming three new Trustees to the Board of Trustees: 

  • Amali de Alwis is the UK Managing Director of Microsoft for Startups, and is the former CEO of Code First: Girls. She is also a Board member at Ada National College for Digital Skills, sits on the Diversity & Inclusion Board at the Institute of Coding, is an Advisory Board member at the Founders Academy, and was a founding member at Tech Talent Charter.
  • Charles Leadbeater is an independent author, a social entrepreneur, and a leading authority on innovation and creativity. He has advised companies, cities, and governments around the world on innovation strategy and has researched and written extensively on innovation in education. Charles is also a Trustee of the Paul Hamlyn Foundation.
  • Dan Labbad is Chief Executive and Executive Member of the Board of The Crown Estate. He was previously at Lendlease, where he was Chief Executive Officer of Europe from 2009. Dan is also a Director of The Hornery Institute and Ark Schools.

New Member: Suranga Chandratillake 

I am also delighted to announce that we have appointed Suranga Chandratillake as a Member of the Raspberry Pi Foundation. Suranga is a technologist, entrepreneur, and investor.

Suranga Chandratillake

He founded the intelligent search company blinkx and is now a General Partner at Balderton Capital. Suranga is a Fellow of the Royal Academy of Engineering and a World Economic Forum Young Global Leader, and he serves on the UK Government’s Council for Science and Technology.

What is a Board of Trustees anyway? 

As a charity, the Raspberry Pi Foundation is governed by a Board of Trustees who is ultimately responsible for what we do and how we are run. It is the Trustees’ job to make sure that we are focused on our mission, which for us means helping more people learn about computing, computer science, and related subjects. The Trustees also have all the usual responsibilities of company directors, including making sure that we use our resources effectively. As Chief Executive, I am accountable to the Board of Trustees. 

We’ve always been fortunate to attract the most amazing people to serve as Trustees and, as volunteers, they are incredibly generous with their time, sharing their expertise and experience on a wide range of issues. They are an important part of the team. Trustees serve for up to two terms of three years so that we always have fresh views and experience to draw on.

How do you appoint Trustees? 

Appointments to the Board of Trustees follow open recruitment and selection processes that are overseen by the Foundation’s Nominations Committee, supported by independent external advisers. Our aim is to appoint Trustees who bring different backgrounds, perspectives, and lived experience, as well as a range of skills. As with all appointments, we consider diversity at every aspect of the recruitment and selection processes.

Formally, Trustees are elected by the Foundation’s Members at our Annual General Meeting. This year’s AGM took place last week on Zoom. Members are also volunteers, and they play an important role in holding the Board of Trustees to account, helping to shape our strategy, and acting as advocates for our mission.

You can see the full list of Trustees and Members on our website.

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Designing the Raspberry Pi Compute Module 4

Raspberry Pi Compute Module 4 designer Dominic Plunkett was kind enough to let us sit him down for a talk with Eben, before writing up his experience of bringing our latest board to life for today’s blog post. Enjoy.

When I joined Raspberry Pi, James, Eben and Gordon already had some ideas on the features they would like to see on the new Compute Module 4, and it was down to me to take these ideas and turn them into a product. Many people think design is a nice linear process: ideas, schematics, PCB, and then final product. In the real world the design process isn’t like this, and to get the best designs I often try something and iterate around the design loop to get the best possible solution within the constraints.

Form factor change

Previous Compute Modules were all in a 200-pin SODIMM form factor, but two important considerations pushed us to think about moving to a different form factor: the need to expose useful interfaces of the BCM2711 that are not present in earlier SoCs, and the desire to add extra components, which meant we needed to route tracks differently to make space on the PCB for the additional parts.

Breaking out BCM2711’s high-speed interfaces

We knew we wanted to get the extra features of the BCM2711 out to the connector so that users could make use of them in their products. High-speed interfaces like PCIe and HDMI are so fast coming out of the BCM2711 that they need special IO pins that can’t also support GPIO: if we were to change the functionality of a GPIO pin to one of the new high-speed signals, this would break backwards compatibility.

We could consider adding some sort of multiplexer to swap between old and new functionality, but this would cost space on the PCB, as well as reducing the integrity of the fast signals. This consideration alone drives the design to a new pinout. We could have tried to use one of the SODIMM connectors with extra pins; while this would give a board with similar dimensions to the existing Compute Modules, it too would break compatibility.

Compute Module 4 mounted on the IO Board
Compute Module 4 mounted on the IO Board

PCB space for additional components

We also wanted to add extra items to the PCB, so PCB space to put the additional parts was an important consideration. If you look carefully at a Compute Module 3 you can see a lot of tracks carrying signals from one side of the SoC to the pins on the edge connector. These tracks take up valuable PCB space, preventing components being fitted there. We could add extra PCB layers to move these tracks from an outer layer to an inner layer, but these extra layers add to the cost of the product.

This was one of the main drivers in changing to having two connectors on different edges of the board: doing so saves having to route tracks all the way across the PCB. So we arrived at a design that incorporated a rough split of which signals were going to end up on each of the connectors. The exact order of the signals wasn’t yet defined.

Trial PCB layouts

We experimented with trial PCB layouts for the Compute Module 4 and the CM4 IO Board to see how easy it would be to route the signals; even at this stage, the final size of the CM4 hadn’t been fixed. Over time, and after juggling parts around the PCB, I came to a sensible compromise. There were lots of things to consider, including the fact that the taller components had to go on the top side of the PCB.

The pinout was constantly being adjusted to an ordering that was a good compromise for both the CM4 and the IO Board. The IO Board layout was a really important consideration: after we made the first prototype boards, we decided to change the pinout slightly to make PCB layout on the IO Board even easier for the end user.

When the prototype Compute Module 4 IO Boards arrived back from manufacture, the connectors hadn’t arrived in time to be assembled by machine, so I fitted them by hand in the lab. Pro tip: if you have to fit connectors by hand, take your time to ensure they are lined up correctly, and use lots of flux to help the solder flow into the joints. Sometimes people use very small soldering iron tips thinking it will help; in fact, one of the goals of soldering is to get heat into the joint, and if the tip is too small it will be difficult to heat the solder joint sufficiently to make a good connection.

Compute Module 4 IO Board

New features

Whilst it was easy to add some headline features like a second HDMI port, other useful features don’t grab as much attention. One example is that we have simplified the powering requirements. Previous Compute Modules required multiple PSUs to power a board, and the power-up sequence had to be exactly correct. Compute Module 4 simply requires a single +5V PSU.

In fact, the simplest possible base board for Compute Module 4 just requires a +5V supply and one of the connectors and nothing else. You would need a CM4 variant with eMMC and wireless connectivity; you can boot the module with the eMMC, wireless connectivity gives you networking, and Bluetooth connectivity gives you access to IO devices. If you do add extra IO devices the CM4 also can provide a +3.3V supply to power those devices, avoiding the need for an external power supply.

We have seen some customers experience issues with adding wireless interfaces to previous Compute Modules, so a really important requirement was to provide the option of wireless support. We wanted to be as flexible as possible, so we have added support for an external antenna. Because radio certification can be a very hard and expensive process, we have a pre-certified external antenna kit that can be supplied with Compute Module 4. This should greatly simplify product certification for end products, although engineering designers should check to make certain of meeting all local requirements.

Antenna Kit and Compute Module 4

PCIe

This is probably the most exciting new interface to come to Compute Module 4. On the existing Raspberry Pi 4, this interface is used internally to add the XHCI controller which provides the USB 3 ports. By providing the PCIe externally, we are giving end users the choice of how they would like to use this interface. Many applications don’t need USB 3 performance, so the end user can make use of it in other ways — for NVMe drives, to take one example.

Ethernet

In order to have wired Ethernet connectivity with previous Compute Modules, you needed to add an external USB-to-Ethernet interface. This adds complexity to the IO board, and one of the aims of the new Compute Module 4 is to make interfacing to it simple. With this in mind, we added a physical Ethernet interface to CM4, and we also took the opportunity to add support for IEEE1588 to this. As a result, adding Gigabit wired networking to CM4 requires only the addition of a magjack; no extra silicon is needed. Because this is a true Gigabit interface, it is also faster than the USB-to-Ethernet interfaces that previous Compute Modules use.

Raspberry Pi Compute Module 4

Open-sourcing the Compute Module 4 IO Board design files

Early on in the process, we decided that we were going to open-source the design files for the Compute Module 4 IO Board. We used our big expensive CAD system for Compute Module 4 itself, and while we could have decided to do the design for the IO Board in the big CAD system too and then port it across to KiCAD, it’s easy to introduce issues in the porting process.

So, instead, we used KiCAD for the IO Board from the start, and the design files that come out of KiCAD are the same ones that we use in manufacture. During development I had both CAD systems running at the same time on the computer.

Easier integration and enhanced possibilities

We have made some big changes to our new Compute Module 4 range, and these should make integration much simpler for our customers. Many interfaces now just need a connector and power, and the new form factor should enable people to design more compact and more powerful products. I look forward to seeing what our customers create over the next few years with Compute Module 4.

High-density connector on board underside

Get your Compute Module 4

The new Raspberry Pi Compute Module 4 is available from our network of Approved Resellers. Head over to the Compute Module 4 product page and select your preferred variant to find your nearest reseller.

Can’t find a reseller near you? No worries. Many of our Approved Resellers ship internationally, so try a few other locations.

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Source: Raspberry Pi – Designing the Raspberry Pi Compute Module 4

Vulkan update: merged to Mesa

Today we have another guest post from Igalia’s Iago Toral, who has spent the past year working on the Mesa graphic driver stack for Raspberry Pi 4.

Four months ago we announced that work on the Vulkan effort for Raspberry Pi 4 (v3dv) was progressing well, and that we were moving the development to an open repository.

vkQuake3 on Raspberry Pi 4

This week, the Vulkan driver for Raspberry Pi 4 has been merged with Mesa upstream, becoming one of the official Vulkan Mesa drivers. This brings several advantages:

  • Easier to find: now anyone willing to test the driver just needs to go to the official Mesa repository
  • Bug tracking: issues/bugs can now be filed on the official Mesa repository bug tracker. If the problem affects other parts of the project, it will be easier for us to involve other Mesa developers.
  • Releasing: v3dv will be included in all Mesa releases. In due course, you will no longer need to go to an external repository to obtain the driver, as it will be included in the Mesa package for your distribution.
  • Maintenance: v3dv will be included in the Mesa Continuous Integration system, so every merge request will be tested to ensure that our driver still builds. More effort can go to new features and bug fixes rather than just keeping up with upstream changes.

Progress, and current status

We said back in June that we were passing over 70,000 tests from the Khronos Conformance Test Suite for Vulkan 1.0, and that we had an implementation for a significant subset of the Vulkan 1.0 API. Now we are passing over 100,000 tests, and have implemented the full Vulkan 1.0 API. Only a handful of CTS tests remain to be fixed.

Sascha Willems’ deferred multisampling demo

This doesn’t mean that our work is done, of course. Although the CTS is a really complete test suite, it is not the same as a real use case. As mentioned some of our updates, we have been testing the driver with Vulkan ports of the original Quake trilogy, but deeper and more detailed testing is needed. So the next step will be to test the driver with more use cases, and fixing any bugs or performance issues that we find during the process.

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Source: Raspberry Pi – Vulkan update: merged to Mesa

Raspberry Pi Compute Module 4 on sale now from $25

It’s become a tradition that we follow each Raspberry Pi model with a system-on-module variant based on the same core silicon. Raspberry Pi 1 gave rise to the original Compute Module in 2014; Raspberry Pi 3 and 3+ were followed by Compute Module 3 and 3+ in 2017 and 2019 respectively. Only Raspberry Pi 2, our shortest-lived flagship product at just thirteen months, escaped the Compute Module treatment.

It’s been sixteen months since we unleashed Raspberry Pi 4 on the world, and today we’re announcing the launch of Compute Module 4, starting from $25.

Over half of the seven million Raspberry Pi units we sell each year go into industrial and commercial applications, from digital signage to thin clients to process automation. Many of these applications use the familiar single-board Raspberry Pi, but for users who want a more compact or custom form factor, or on-board eMMC storage, Compute Module products provide a simple way to move from a Raspberry Pi-based prototype to volume production.

A step change in performance

Built on the same 64-bit quad-core BCM2711 application processor as Raspberry Pi 4, our Compute Module 4 delivers a step change in performance over its predecessors: faster CPU cores, better multimedia, more interfacing capabilities, and, for the first time, a choice of RAM densities and a wireless connectivity option.

Raspberry Pi Compute Module 4
Raspberry Pi Compute Module 4

You can find detailed specs here, but let’s run through the highlights:

  • 1.5GHz quad-core 64-bit ARM Cortex-A72 CPU
  • VideoCore VI graphics, supporting OpenGL ES 3.x
  • 4Kp60 hardware decode of H.265 (HEVC) video
  • 1080p60 hardware decode, and 1080p30 hardware encode of H.264 (AVC) video
  • Dual HDMI interfaces, at resolutions up to 4K
  • Single-lane PCI Express 2.0 interface
  • Dual MIPI DSI display, and dual MIPI CSI-2 camera interfaces
  • 1GB, 2GB, 4GB or 8GB LPDDR4-3200 SDRAM
  • Optional 8GB, 16GB or 32GB eMMC Flash storage
  • Optional 2.4GHz and 5GHz IEEE 802.11b/g/n/ac wireless LAN and Bluetooth 5.0
  • Gigabit Ethernet PHY with IEEE 1588 support
  • 28 GPIO pins, with up to 6 × UART, 6 × I2C and 5 × SPI
Compute Module 4 Lite (without eMMC Flash memory)
Compute Module 4 Lite, our variant without eMMC Flash memory

New, more compact form factor

Compute Module 4 introduces a brand new form factor, and a compatibility break with earlier Compute Modules. Where previous modules adopted the JEDEC DDR2 SODIMM mechanical standard, with I/O signals on an edge connector, we now bring I/O signals to two high-density perpendicular connectors (one for power and low-speed interfaces, and one for high-speed interfaces).

This significantly reduces the overall footprint of the module on its carrier board, letting you achieve smaller form factors for your products.

High-density connector on board underside
High-density connector on board underside

32 variants

With four RAM options, four Flash options, and optional wireless connectivity, we have a total of 32 variants, with prices ranging from $25 (for the 1GB RAM, Lite, no wireless variant) to $90 (for the 8GB RAM, 32GB Flash, wireless variant).

We’re very pleased that the four variants with 1GB RAM and no wireless keep the same price points ($25, $30, $35, and $40) as their Compute Module 3+ equivalents: once again, we’ve managed to pack a lot more performance into the platform without increasing the price.

You can find the full price list in the Compute Module 4 product brief.

Compute Module 4 IO Board

To help you get started with Compute Module 4, we are also launching an updated IO Board. Like the IO boards for earlier Compute Module products, this breaks out all the interfaces from the Compute Module to standard connectors, providing a ready-made development platform and a starting point for your own designs.

Compute Module 4 IO Board
Compute Module 4 IO Board

The IO board provides:

  • Two full-size HDMI ports
  • Gigabit Ethernet jack
  • Two USB 2.0 ports
  • MicroSD card socket (only for use with Lite, no-eMMC Compute Module 4 variants)
  • PCI Express Gen 2 x1 socket
  • HAT footprint with 40-pin GPIO connector and PoE header
  • 12V input via barrel jack (supports up to 26V if PCIe unused)
  • Camera and display FPC connectors
  • Real-time clock with battery backup

CAD for the IO board is available in KiCad format. You may recall that a few years ago we made a donation to support improvements to KiCad’s differential pair routing and track length control features; now you can use this feature-rich, open-source PCB layout package to design your own Compute Module carrier board.

Compute Module 4 mounted on the IO Board
Compute Module 4 mounted on the IO Board

In addition to serving as a development platform and reference design, we expect the IO board to be a finished product in its own right: if you require a Raspberry Pi that supports a wider range of input voltages, has all its major connectors in a single plane, or allows you to attach your own PCI Express devices, then Compute Module 4 with the IO Board does what you need.

We’ve set the price of the bare IO board at just $35, so a complete package including a Compute Module starts from $60.

Compute Module 4 Antenna Kit

We expect that most users of wireless Compute Module variants will be happy with the on-board PCB antenna. However, in some circumstances – for example, where the product is in a metal case, or where it is not possible to provide the necessary ground plane cut-out under the module – an external antenna will be required. The Compute Module 4 Antenna Kit comprises a whip antenna, with a bulkhead screw fixture and U.FL connector to attach to the socket on the module.

Antenna Kit and Compute Module 4
Antenna Kit and Compute Module 4

When using ether the Antenna Kit or the on-board antenna, you can take advantage of our modular certification to reduce the conformance testing costs for your finished product. And remember, the Raspberry Pi Integrator Programme is there to help you get your Compute Module-based product to market.

Our most powerful Compute Module

This is our best Compute Module yet. It’s also our first product designed by Dominic Plunkett, who joined us almost exactly a year ago.

I sat down with Dominic last week to discuss Compute Module 4 in greater detail, and you can find the video of our conversation here. Dominic will also be sharing more technical detail in the blog tomorrow.

In the meantime, check out the Compute Module 4 page for the datasheet and other details, and start thinking about what you’ll build with Compute Module 4.

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Source: Raspberry Pi – Raspberry Pi Compute Module 4 on sale now from

Pumpkin Pi Build Monitor

Following on from Rob Zwetsloot’s Haunted House Hacks in the latest issue of The MagPi magazine, GitHub’s Martin Woodward has created a spooky pumpkin that warns you about the thing programmers find scariest of all — broken builds. Here’s his guest post describing the project:

“When you are browsing code looking for open source projects, seeing a nice green passing build badge in the ReadMe file lets you know everything is working with the latest version of that project. As a programmer you really don’t want to accidentally commit bad code, which is why we often set up continuous integration builds that constantly check the latest code in our project.”

“I decided to create a 3D-printed pumpkin that would hold a Raspberry Pi Zero with an RGB LED pHat on top to show me the status of my build for Halloween. All the code is available on GitHub alongside the 3D printing models which are also available on Thingiverse.”

Components

  • Raspberry Pi Zero (I went for the WH version to save me soldering on the header pins)
  • Unicorn pHat from Pimoroni
  • Panel mount micro-USB extension
  • M2.5 hardware for mounting (screws, male PCB standoffs, and threaded inserts)

“For the 3D prints, I used a glow-in-the-dark PLA filament for the main body and Pi holder, along with a dark green PLA filament for the top plug.”

“I’ve been using M2.5 threaded inserts quite a bit when printing parts to fit a Raspberry Pi, as it allows you to simply design a small hole in your model and then you push the brass thread into the gap with your soldering iron to melt it securely into place ready for screwing in your device.”

Threaded insert

“Once the inserts are in, you can screw the Raspberry Pi Zero into place using some brass PCB stand-offs, place the Unicorn pHAT onto the GPIO ports, and then screw that down.”

pHAT install

“Then you screw in the panel-mounted USB extension into the back of the pumpkin, connect it to the Raspberry Pi, and snap the Raspberry Pi holder into place in the bottom of your pumpkin.”

Inserting the base

Code along with Martin

“Now you are ready to install the software.  You can get the latest version from my PumpkinPi project on GitHub. “

“Format the micro SD Card and install Raspberry Pi OS Lite. Rather than plugging in a keyboard and monitor, you probably want to do a headless install, configuring SSH and WiFi by dropping an ssh file and a wpa_supplicant.conf file onto the root of the SD card after copying over the Raspbian files.”

“You’ll need to install the Unicorn HAT software, but they have a cool one-line installer that takes care of all the dependencies including Python and Git.”

curl -sS https://get.pimoroni.com/unicornhat | bash

“In addition, we’ll be using the requests module in Python which you can install with the following command:”

sudo pip install requests

“Next you want to clone the git repo.”

git clone https://github.com/martinwoodward/PumpkinPi.git

“You then need to modify the settings to point at your build badge. First of all copy the sample settings provided in the repo:”

cp ~/PumpkinPi/src/local_settings.sample ~/PumpkinPi/src/local_settings.py

“Then edit the BADGE_LINK variable and point at the URL of your build badge.”

# Build Badge for the build you want to monitor

BADGE_LINK = "https://github.com/martinwoodward/calculator/workflows/CI/badge.svg?branch=main"

# How often to check (in seconds). Remember - be nice to the server. Once every 5 minutes is plenty.

REFRESH_INTERVAL = 300

“Finally you can run the script as root:”

sudo python ~/PumpkinPi/src/pumpkinpi.py &amp;

“Once you are happy everything is running how you want, don’t forget you can run the script at boot time. The easiest way to do this is to use crontab. See this cool video from Estefannie to learn more. But basically you do sudo crontab -e then add the following:”

@reboot /bin/sleep 10 ; /usr/bin/python /home/pi/PumpkinPi/src/pumpkinpi.py &amp;

“Note that we are pausing for 10 seconds before running the Python script. This is to allow the WiFi network to connect before we check on the state of our build.”

“The current version of the pumpkinpi script works with all the SVG files produced by the major hosted build providers, including GitHub Actions, which is free for open source projects. But if you want to improve the code in any way, I’m definitely accepting pull requests on it.”

“Using the same hardware you could monitor lots of different things, such as when someone posts on Twitter, what the weather will be tomorrow, or maybe just code your own unique multi-coloured display that you can leave flickering in your window.”

“If you build this project or create your own pumpkin display, I’d love to see pictures. You can find me on Twitter @martinwoodward and on GitHub.”

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Source: Raspberry Pi – Pumpkin Pi Build Monitor

Join the UK Bebras Challenge 2020 for schools!

The annual UK Bebras Computational Thinking Challenge for schools, brought to you by the Raspberry Pi Foundation and Oxford University, is taking place this November!

UK Bebras Challenge logo

The Bebras Challenge is a great way for your students to practise their computational thinking skills while solving exciting, accessible, and puzzling questions. Usually this 40-minute challenge would take place in the classroom. However, this year for the first time, your students can participate from home too!

If your students haven’t entered before, now is a great opportunity for them to get involved: they don’t need any prior knowledge. 

Do you have any students who are up for tackling the Bebras Challenge? Then register your school today!

School pupils in a computing classroom

What you need to know about the Bebras Challenge

  • It’s a great whole-school activity open to students aged 6 to 18, in different age group categories.
  • It’s completely free!
  • The closing date for registering your school is 30 October.
  • Let your students complete the challenge between 2 and 13 November 2020.
  • The challenge is made of a set of short tasks, and completing it takes 40 minutes.
  • The challenge tasks focus on logical thinking and do not require any prior knowledge of computer science.
  • There are practice questions to help your students prepare for the challenge.
  • This year, students can take part at home (please note they must still be entered through their school).
  • All the marking is done for you! The results will be sent to you the week after the challenge ends, along with the answers, so that you can go through them with your students.

“Thank you for another super challenge. It’s one of the highlights of my year as a teacher. Really, really appreciate the high-quality materials, website, challenge, and communication. Thank you again!”

– A UK-based teacher

Support your students to develop their computational thinking skills with Bebras materials

Bebras is an international challenge that started in Lithuania in 2004 and has grown into an international event. The UK became involved in Bebras for the first time in 2013, and the number of participating students has increased from 21,000 in the first year to more than 260,000 last year! Internationally, nearly 3 million learners took part in 2019. 

Bebras is a great way to engage your students of all ages in problem-solving and give them a taste of what computing is all about. In the challenge results, computing principles are highlighted, so Bebras can be educational for you as a teacher too.

The annual Bebras Challenge is only one part of the equation: questions from previous years are available as a resource that you can use to create self-marking quizzes for your classes. You can use these materials throughout the year to help you to deliver the computational thinking part of your curriculum!

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Source: Raspberry Pi – Join the UK Bebras Challenge 2020 for schools!

Raspberry Pi High Quality security camera

DJ from the element14 community shows you how to build a red-lensed security camera in the style of Portal 2 using the Raspberry Pi High Quality Camera.

The finished camera mounted on the wall

Portal 2 is a puzzle platform game developed by Valve — a “puzzle game masquerading as a first-person shooter”, according to Forbes.

DJ playing with the Raspberry Pi High Quality Camera

Kit list

No code needed!

DJ was pleased to learn that you don’t need to write any code to make your own security camera, you can just use a package called motionEyeOS. All you have to do is download the motionEyeOS image, pop the flashed SD card into your Raspberry Pi, and you’re pretty much good to go.

Dj got everything set up on a 5″ screen attached to the Raspberry Pi

You’ll find that the default resolution is 640×480, so it will show up as a tiny window on your monitor of choice, but that can be amended.

Simplicity

While this build is very simple electronically, the 20-part 3D-printed shell is beautiful. A Raspberry Pi is positioned on a purpose-built platform in the middle of the shell, connected to the Raspberry Pi High Quality Camera, which sits at the front of that shell, peeking out.

All the 3D printed parts ready to assemble

The 5V power supply is routed through the main shell into the base, which mounts the build to the wall. In order to keep the Raspberry Pi cool, DJ made some vent holes in the lens of the shell. The red LED is routed out of the side and sits on the outside body of the shell.

Magnetising

Raspberry Pi 4 (centre) and Raspberry Pi High Quality Camera (right) sat inside the 3D printed shell

This build is also screwless: the halves of the shell have what look like screw holes along the edges, but they are actually 3mm neodymium magnets, so assembly and repair is super easy as everything just pops on and off.

The final picture (that’s DJ!)

You can find all the files you need to recreate this build, or you can ask DJ a question, at element14.com/presents.

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Source: Raspberry Pi – Raspberry Pi High Quality security camera

AI-Man: a handy guide to video game artificial intelligence

Discover how non-player characters make decisions by tinkering with this Unity-based Pac-Man homage. Paul Roberts wrote this for the latest issue of Wireframe magazine.

From the first video game to the present, artificial intelligence has been a vital part of the medium. While most early games had enemies that simply walked left and right, like the Goombas in Super Mario Bros., there were also games like Pac-Man, where each ghost appeared to move intelligently. But from a programming perspective, how do we handle all the different possible states we want our characters to display?

Here’s AI-Man, our homage to a certain Namco maze game. You can switch between AI types to see how they affect the ghosts’ behaviours.

For example, how do we control whether a ghost is chasing Pac-Man, or running away, or even returning to their home? To explore these behaviours, we’ll be tinkering with AI-Man – a Pac-Man-style game developed in Unity. It will show you how the approaches discussed in this article are implemented, and there’s code available for you to modify and add to. You can freely download the AI-Man project here. One solution to managing the different states a character can be in, which has been used for decades, is a finite state machine, or FSM for short. It’s an approach that describes the high-level actions of an agent, and takes its name simply from the fact that there are a finite number of states from which to transition between, with each state only ever doing one thing.

Altered states

To explain what’s meant by high level, let’s take a closer look at the ghosts in Pac-Man. The highlevel state of a ghost is to ‘Chase’ Pac-Man, but the low level is how the ghost actually does this. In Pac-Man, each ghost has its own behaviour in which it hunts the player down, but they’re all in the same high-level state of ‘Chase’. Looking at Figure 1, you can see how the overall behaviour of a ghost can be depicted extremely easily, but there’s a lot of hidden complexity. At what point do we transition between states? What are the conditions on moving between states across the connecting lines? Once we have this information, the diagram can be turned into code with relative ease. You could use simple switch statements to achieve this, or we could achieve the same using an object-oriented approach.

Figure 1: A finite state machine

Using switch statements can quickly become cumbersome the more states we add, so I’ve used the object-oriented approach in the accompanying project, and an example code snippet can be seen in Code Listing 1. Each state handles whether it needs to transition into another state, and lets the state machine know. If a transition’s required, the Exit() function is called on the current state, before calling the Enter() function on the new state. This is done to ensure any setup or cleanup is done, after which the Update() function is called on whatever the current state is. The Update()function is where the low-level code for completing the state is processed. For a project as simple as Pac-Man, this only involves setting a different position for the ghost to move to.

Hidden complexity

Extending this approach, it’s reasonable for a state to call multiple states from within. This is called a hierarchical finite state machine, or HFSM for short. An example is an agent in Call of Duty: Strike Team being instructed to seek a stealthy position, so the high-level state is ‘Find Cover’, but within that, the agent needs to exit the dumpster he’s currently hiding in, find a safe location, calculate a safe path to that location, then repeatedly move between points on that path until he reaches the target position.

FSMs can appear somewhat predictable as the agent will always transition into the same state. This can be accommodated for by having multiple options that achieve the same goal. For example, when the ghosts in our Unity project are in the ‘Chase’ state, they can either move to the player, get in front of the player, or move to a position behind the player. There’s also an option to move to a random position. The FSM implemented has each ghost do one of these, whereas the behaviour tree allows all ghosts to switch between the options every ten seconds. A limitation of the FSM approach is that you can only ever be in a single state at a particular time. Imagine a tank battle game where multiple enemies can be engaged. Simply being in the ‘Retreat’ state doesn’t look smart if you’re about to run into the sights of another enemy. The worst-case scenario would be our tank transitions between ‘Attack’ and ‘Retreat’ states on each frame – an issue known as state thrashing – and gets stuck, and seemingly confused about what to do in this situation. What we need is away to be in multiple states at the same time: ideally retreating from tank A, whilst attacking tank B. This is where fuzzy finite state machines, or FFSM for short, come in useful.

This approach allows you to be in a particular state to a certain degree. For example, my tank could be 80% committed to the Retreat state (avoid tank A), and 20% committed to the Attack state (attack tank B). This allows us to both Retreat and Attack at the same time. To achieve this, on each update, your agent needs to check each possible state to determine its degree of commitment, and then call each of the active states’ updates. This differs from a standard FSM, where you can only ever be in a single state. FFSMs can be in none, one, two, or however many states you like at one time. This can prove tricky to balance, but it does offer an alternative to the standard approach.

No memory

Another potential issue with an FSM is that the agent has no memory of what they were previously doing. Granted, this may not be important: in the example given, the ghosts in Pac-Man don’t care about what they were doing, they only care about what they are doing, but in other games, memory can be extremely important. Imagine instructing a character to gather wood in a game like Age of Empires, and then the character gets into a fight. It would be extremely frustrating if the characters just stood around with nothing to do after the fight had concluded, and for the player to have to go back through all these characters and reinstruct them after the fight is over. It would be much better for the characters to return to their previous duties.

“FFSMs can be in one, none,

two, or however many states

you like.”

We can incorporate the idea of memory quite easily by using the stack data structure. The stack will hold AI states, with only the top-most element receiving the update. This in effect means that when a state is completed, it’s removed from the stack and the previous state is then processed. Figure 2 depicts how this was achieved in our Unity project. To differentiate the states from the FSM approach, I’ve called them tasks for the stackbased implementation. Looking at Figure 2, it shows how (from the bottom), the ghost was chasing the player, then the player collected a power pill, which resulted in the AI adding an Evade_Task – this now gets the update call, not the Chase_Task. While evading the player, the ghost was then eaten.

At this point, the ghost needed to return home, so the appropriate task was added. Once home, the ghost needed to exit this area, so again, the relevant task was added. At the point the ghost exited home, the ExitHome_Task was removed, which drops processing back to MoveToHome_Task. This was no longer required, so it was also removed. Back in the Evade_Task, if the power pill was still active, the ghost would return to avoiding the player, but if it had worn off, this task, in turn, got removed, putting the ghost back in its default task of Chase_Task, which will get the update calls until something else in the world changes.

Figure 2: Stack-based finite state machine.

Behaviour trees

In 2002, Halo 2 programmer Damian Isla expanded on the idea of HFSM in a way that made it more scalable and modular for the game’s AI. This became known as the behaviour tree approach. It’s now a staple in AI game development. The behaviour tree is made up of nodes, which can be one of three types – composite, decorator, or leaf nodes. Each has a different function within the tree and affects the flow through the tree. Figure 3 shows how this approach is set up for our Unity project. The states we’ve explored so far are called leaf nodes. Leaf nodes end a particular branch of the tree and don’t have child nodes – these are where the AI behaviours are located. For example, Leaf_ExitHome, Leaf_Evade, and Leaf_ MoveAheadOfPlayer all tell the ghost where to move to. Composite nodes can have multiple child nodes and are used to determine the order in which the children are called. This could be in the order in which they’re described by the tree, or by selection, where the children nodes will compete, with the parent node selecting which child node gets the go-ahead. Selector_Chase allows the ghost to select a single path down the tree by choosing a random option, whereas Sequence_ GoHome has to complete all the child paths to complete its behaviour.

Code Listing 2 shows how simple it is to choose a random behaviour to use – just be sure to store the index for the next update. Code Listing 3 demonstrates how to go through all child nodes, and to return SUCCESS only when all have completed, otherwise the status RUNNING is returned. FAILURE only gets returned when a child node itself returns a FAILURE status.

Complex behaviours

Although not used in our example project, behaviour trees can also have nodes called decorators. A decorator node can only have a single child, and can modify the result returned. For example, a decorator may iterate the child node for a set period, perhaps indefinitely, or even flip the result returned from being a success to a failure. From what first appears to be a collection of simple concepts, complex behaviours can then develop.

Figure 3: Behaviour tree

Video game AI is all about the illusion of intelligence. As long as the characters are believable in their context, the player should maintain their immersion in the game world and enjoy the experience we’ve made. Hopefully, the approaches introduced here highlight how even simple approaches can be used to develop complex characters. This is just the tip of the iceberg: AI development is a complex subject, but it’s also fun and rewarding to explore.

Wireframe #43, with the gorgeous Sea of Stars on the cover.

The latest issue of Wireframe Magazine is out now. available in print from the Raspberry Pi Press onlinestore, your local newsagents, and the Raspberry Pi Store, Cambridge.

You can also download the PDF directly from the Wireframe Magazine website.

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Congratulations Carrie Anne Philbin, MBE

We are delighted to share the news that Carrie Anne Philbin, Raspberry Pi’s Director of Educator Support, has been awarded an MBE for her services to education in the Queen’s Birthday Honours 2020.

Carrie Anne Philbin MBE
Carrie Anne Philbin, newly minted MBE

Carrie Anne was one of the first employees of the Raspberry Pi Foundation and has helped shape our educational programmes over the past six years. Before joining the Foundation, Carrie Anne was a computing teacher, YouTuber, and author.

She’s also a tireless champion for diversity and inclusion in computing; she co-founded a grassroots movement of computing teachers dedicated to diversity and inclusion, and she has mentored young girls and students from disadvantaged backgrounds. She is a fantastic role model and source of inspiration to her colleagues, educators, and young people. 

From history student to computing teacher and YouTuber

As a young girl, Carrie Anne enjoyed arts and crafts and when her dad bought the family a Commodore 64, she loved the graphics she could make on it. She says, “I vividly remember typing in the BASIC commands to create a train that moved on the screen with my dad.” Being able to express her creativity through digital patterns sparked her interest in technology.

After studying history at university, Carrie Anne followed her passion for technology and became an ICT technician at a secondary school, where she also ran several extra-curricular computing clubs for the students. Her school encouraged and supported her to apply for the Graduate Teacher Programme, and she qualified within two years.

Carrie Anne admits that her first experience in a new school as a newly qualified teacher was “pretty terrifying”, and she says her passion for the subject and her sense of humour are what got her through. The students she taught in her classroom still inspire her today.

Showing that computing is for everyone

As well as co-founding CAS #include, a diversity working group for computing teachers, Carrie Anne started the successful YouTube channel Geek Gurl Diaries. Through video interviews with women working in tech and hands-on computer science tutorials, Carrie Anne demonstrates that computing is fun and that it’s great to be a girl who likes computers.

Carrie Anne Philbin MBE sitting at a disk with physical computing equipment

On the back of her own YouTube channel’s success, Carrie Anne was invited to host the Computer Science video series on Crash Course, the extremely popular educational YouTube channel created by Hank and John Green. There, her 40+ videos have received over 2 million views so far.

Discovering the Raspberry Pi Foundation

Carrie Anne says that the Raspberry Pi computer brought her to the Raspberry Pi Foundation, and that she stayed “because of the community and the Foundation’s mission“. She came across the Raspberry Pi while searching for new ways to engage her students in computing, and joined a long waiting list to get her hands on the single-board computer. After her Raspberry Pi finally arrived, she carried it in her handbag to community meetups to learn how other people were using it in education.

Carrie Anne Philbin
Carrie Anne with her book Adventures in Raspberry Pi

Since joining the Foundation, Carrie Anne has helped to build an incredible team, many of them also former computing teachers. Together they have trained thousands of educators and produced excellent resources that are used by teachers and learners around the world. Most recently, the team created the Teach Computing Curriculum of over 500 hours of free teaching resources for primary and secondary teachers; free online video lessons for students learning at home during the pandemic (in partnership with Oak National Academy); and Isaac Computer Science, a free online learning platform for A level teachers and students.

On what she wants to empower young people to do

Carrie Anne says, “We’re living in an ever-changing world that is facing many challenges right now: climate change, democracy and human rights, oh and a global pandemic. These are issues that young people care about. I’ve witnessed this year after year at our international Coolest Projects technology showcase event for young people, where passionate young creators present the tech solutions they are already building to address today’s and tomorrow’s problems. I believe that equipped with a deeper understanding of technology, young people can change the world for the better, in ways we’ve not even imagined.” 

Carrie Anne has already achieved a huge amount in her career, and we honestly believe that she is only just getting started. On behalf of all your colleagues at the Foundation and all the educators and young people whose lives you’ve changed, congratulations Carrie Anne! 

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Scroll text across your face mask with NeoPixel and Raspberry Pi

Have you perfected your particular combination of ‘eye widening then squinting’ to let people know you’re smiling at them behind your mask? Or do you need help expressing yourself from this text-scrolling creation by Caroline Dunn?

The mask running colourful sample code

What’s it made of?

The main bits of hardware need are a Raspberry Pi 3 or Raspberry Pi 4 or Raspberry Pi Zero W (or a Zero WH with pre-soldered GPIO header if you don’t want to do soldering yourself), and an 8×8 Flexible NeoPixel Matrix with individually addressable LEDs. The latter is a two-dimensional grid of NeoPixels, all controlled via a single microcontroller pin.

Raspberry Pi and the NeoPixel Matrix (bottom left) getting wired up

The NeoPixel Matrix is attached to a cloth face that which has a second translucent fabric layer. The translucent layer is to sew your Raspberry Pi project to, the cloth layer underneath is a barrier for germs.

You’ll need a separate 5V power source for the NeoPixel Matrix. Caroline used a 5V power bank, which involved some extra fiddling with cutting up and stripping an old USB cable. You may want to go for a purpose-made traditional power supply for ease.

Running the text

To prototype, Caroline connected the Raspberry Pi computer to the NeoPixel Matrix via a breadboard and some jumper wires. At this stage of your own build, you check everything is working by running this sample code from Adafruit, which should get your NeoPixel Matrix lighting up like a rainbow.

The internal website on the left

Once you’ve got your project up and running, you can ditch the breadboard and wires and set up the key script, app.py, to run on boot.

Going mobile

To change the text scrolling across your mask, you use the internal website that’s part of Caroline’s code.

And for a truly mobile solution, you can access the internal website via mobile phone by hooking up your Raspberry Pi using your phone’s hotspot functionality. Then you can alter the scrolling text while you’re out and about.

Caroline wearing the 32×8 version

Caroline also created a version of her project using a 32×8 Neopixel Matrix, which fits on the across the headband of larger plastic face visors.

If you want to make this build for yourself, you’d do well to start with the very nice in-depth walkthrough Caroline created. It’s only three parts; you’ll be fine.

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How teachers train in Computing with our free online courses

Since 2017 we’ve been training Computing educators in England and around the world through our suite of free online courses on FutureLearn. Thanks to support from Google and the National Centre for Computing Education (NCCE), all of these courses are free for anyone to take, whether you are a teacher or not!

An illustration of a bootcamp for computing teachers

We’re excited that Computer Science educators at all stages in their computing journey have embraced our courses — from teachers just moving into the field to experienced educators looking for a refresher so that they can better support their colleagues.

Hear from two teachers about their experience of training with our courses and how they are benefitting!

Moving from Languages to IT to Computing

Rebecca Connell started out as a Modern Foreign Languages teacher, but now she is Head of Computing at The Cowplain School, a 11–16 secondary school in Hampshire.

Computing teacher Rebecca Connell
Computing teacher Rebecca finds our courses “really useful in building confidence and taking [her] skills further”.

Although she had plenty of experience with Microsoft Office and was happy teaching IT, at first she was daunted by the technical nature of Computing:

“The biggest challenge for me has been the move away from an IT to a Computing curriculum. To say this has been a steep learning curve is an understatement!”

However, Rebecca has worked with our courses to improve her coding knowledge, especially in Python:

“Initially, I undertook some one-day programming courses in Python. Recently, I have found the Raspberry Pi courses to be really useful in building confidence and taking my skills further. So far, I have completed Programming 101 — great for revision and teaching ideas — and am now into Programming 102.”

GCSE Computing is more than just programming, and our courses are helping Rebecca develop the rest of her Computing knowledge too:

“I am now taking some online Raspberry Pi courses on computer systems and networks to firm up my knowledge — my greatest fear is saying something that’s not strictly accurate! These courses have some good ideas to help explain complex concepts to students.”

She also highly rates the new free Teach Computing Curriculum resources we have developed for the NCCE:

“I really like the new resources and supporting materials from Raspberry Pi — these have really helped me to look again at our curriculum. They are easy to follow and include everything you need to take students forward, including lesson plans.”

And Rebecca’s not the only one in her department who is benefitting from our courses and resources:

“Our department is supported by an excellent PE teacher who delivers lessons in Years 7, 8, and 9. She has enjoyed completing some of the Raspberry Pi courses to help her to deliver the new curriculum and is also enjoying her learning journey.”

Refreshing and sharing your knowledge

Julie Price, a CAS Master Teacher and NCCE Computer Science Champion, has been “engaging with the NCCE’s Computer Science Accelerator programme, [to] be in a better position to appreciate and help to resolve any issues raised by fellow participants.”

Computing teacher Julie Price
Computer science teacher Julie Price says she is “becoming addicted” to our online courses!

“I have encountered new learning for myself and also expressions of very familiar content which I have found to be seriously impressive and, in some cases, just amazing. I must say that I am becoming addicted to the Raspberry Pi Foundation’s online courses!”

She’s been appreciating the open nature of the courses, as we make all of the materials free to use under the Open Government Licence:

“Already I have made very good use of a wide range of the videos, animations, images, and ideas from the Foundation’s courses.”

Julie particularly recommends the Programming Pedagogy in Secondary Schools: Inspiring Computing Teaching course, describing it as “a ‘must’ for anyone wishing to strengthen their key stage 3 programming curriculum.”

Join in and train with us

Rebecca and Julie are just 2 of more than 140,000 active participants we have had on our online courses so far!

With 29 courses to choose from (and more on the way!), from Introduction to Web Development to Robotics with Raspberry Pi, we have something for everyone — whether you’re a complete beginner or an experienced computer science teacher. All of our courses are free to take, so find one that inspires you, and let us support you on your computing journey, along with Google and the NCCE.

If you’re a teacher in England, you are eligible for free course certification from FutureLearn via the NCCE.

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Haunted House hacks

Spookify your home in time for Halloween with Rob Zwetsloot and these terror-ific projects!

We picked four of our favourites from a much longer feature in the latest issue of The MagPi magazine, so make sure you check it out if you need more Haunted House hacks in your life.

Raspberry Pi Haunted House

This project is a bit of a mixture of indoors and outdoors, with a doorbell on the house activating a series of spooky effects like a creaking door, ‘malfunctioning’ porch lights, and finally a big old monster mash in the garage.

A Halloween themed doorbell

MagPi magazine talked to its creator Stewart Watkiss about it a few years ago and he revealed how he used a PiFace HAT to interface with home automation techniques to create the scary show, although it can be made much easier these days thanks to Energenie. Our favourite part, though, is still the Home Alone-esque monster party that caps it off.

Check it our for yourself here.

Eye of Sauron

It’s a very nice-looking build as well

The dreaded dark lord Sauron from Lord of the Rings watched over Middle-earth in the form of a giant flaming eye atop his black tower, Barad-dûr. Mike Christian’s version sits on top of a shed in Saratoga, CA.

The eye of sauron on top of a barn lit in red lights
Atop the shed with some extra light effects, it looks very scary

It makes use of the Snake Eyes Bonnet from Adafruit, with some code modifications and projecting onto a bigger eye. Throw in some cool lights and copper wires and you get a nice little effect, much like that from the films.

There are loads more cool photos on Mike’s original project page.

Raspberry Pi-powered Jack-o-Lantern

We love the eyes and scary sounds in this version that seem to follow you around

A classic indoor Halloween decoration (and outdoor, according to American movies) is the humble Jack-o’-lantern. While you could carve your own for this kind of project (and we’ve seen many people do so), this version uses a pre-cut, 3D-printed pumpkin.

3D printed pumpkin glowing orange
The original 3D print lit with a single source is still fairly scary

If you want to put one outside as well, we highly recommend you add some waterproofing or put it under a porch of some kind, especially if you live in the UK.

Here’s a video about the project by the maker.

Scary door

You’re unlikely to trick someone already in your house with a random door that has appeared out of nowhere, but while they’re investigating they’ll get the scare of their life. This door was created as a ‘sequel’ to a Scary Porch, and has a big monitor where a window might be in the door. There’s also an array of air-pistons just behind the door to make it sound like someone is trying to get out.

There are various videos that can play on the door screen, and they’re randomised so any viewers won’t know what to expect. This one also uses relays, so be careful.

This project is the brainchild of the element14 community and you can read more about how it was made here.

The MagPi magazine is out now, available in print from the Raspberry Pi Press onlinestore, your local newsagents, and the Raspberry Pi Store, Cambridge.

You can also download the PDF directly from the MagPi magazine website.

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Build an e-paper to-do list with Raspberry Pi

James Bruxton (or @xrobotosuk on Instagram) built an IoT-controlled e-paper message board using Raspberry Pi. Updating it is easy: just edit a Google sheet, and the message board will update with the new data.

Harnessing Google power

This smart message board uses e-paper, which has very low power consumption. Combining this with the Google Docs API (which allows you to write code to read and write to Google Docs) and Raspberry Pi makes it possible to build a message board that polls a Google Sheet and updates whenever there’s new data. This guide helped James write the Google Docs API code.

We’ll do #4 for you, James!

Why e-paper?

James’s original plan was to hook up his Raspberry Pi to a standard monitor and use Google Docs so people could update the display via mobile app. However, a standard monitor consumes a lot of power, due to its backlight, and if you set it to go into sleep mode, people would just walk past it and not see updates to the list unless they remember to wake the device up.

Raspberry Pi wearing its blue e-paper HAT on the left, which connects to the display on the right via a ribbon cable

Enter e-paper (the same stuff used for Kindle devices), which only consumes power when it’s updating. Once you’ve got the info you want on the e-paper, you can even disconnect it entirely from your power source and the screen will still display whatever the least update told it to. James’s top tip for your project: go for the smallest e-paper display possible, as those things are expensive. He went with this one, which comes with a HAT for Raspberry Pi and a ribbon cable to connect the two.

The display disconnected from any power and still clearly readable

The HAT has an adaptor for plugging into the Raspberry Pi GPIO pins, and a breakout header for the SPI pins. James found it’s not as simple as enabling the SPI on his Raspberry Pi and the e-paper display springing to life: you need a bit of code to enable the SPI display to act as the main display for the Raspberry Pi. Luckily, the code for this is on the wiki of Waveshare, the producer of HAT and display James used for this project.

Making it pretty

A 3D-printed case, which looks like a classic photo frame but with a hefty in-built stand to hold it up and provide enough space for the Raspberry Pi to sit on, is home to James’s finished smart to-do list. The e-paper is so light and thin it can just be sticky-taped into the frame.

The roomy frame stand

James’s creation is powered by Raspberry Pi 4, but you don’t need that much power, and he’s convinced you’ll be fine with any Raspberry Pi model that has 40 GPIO pins.

Extra points for this maker, as he’s put all the CAD files and code you’ll need to make your own e-paper message board on GitHub.

If you’re into e-paper stuff but are wedded to your handwritten to-do lists, then why not try building this super slow movie player instead? The blog squad went *nuts* for it when we posted it last month.

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