Building a low cost Foyer Screen System with Web Apps and Raspberry Pis

Watershed is a cultural cinema, digital creativity centre, events venue and café. This means there’s a lot going on, every day.

Making our audience aware of what’s happening is a difficult task – and even more so in the “digital age”. ‘Having a web site’ used to be the cutting edge thing to do, but that’s increasingly irrelevant in a ‘multi-platform’ world. We now live in an age where there are so many digital platforms to choose from, and to build audience-facing systems you need to choose your strategy more carefully.

Watershed’s ICT department have been thinking about this a lot lately, especially because it was time to upgrade our old foyer screen signage system. Frequent visitors to Watershed will undoubtedly recognize the big screens as you walk up the main stairs. These are important because they contain a lot of information for our visitors: what’s on, what’s coming up and where events are happening. They are vital, especially when it’s busy.

However, over the last couple of years the technology we used to run them was becoming more and more obsolete. Behind the screens lived an old desktop PC stuffed with graphics cards, which was run constantly. Its software consisted of an antiquated version of Firefox (to display fullscreen HTML), Javascript and an old Web Objects API (for sourcing ‘what’s on’ data).

Inevitably, after eight years of faithful service, it eventually died.

Luckily, for the ICT department, we knew this was coming. Within two hours (and much running about) we had replaced the whole foyer screen system with some new exciting technology:  a new foyer screen ‘Web Application’ and some Raspberry Pis.

Enter foyer screens 2.0:

Our new Foyer Screen Display Setup

What’s On Today Web Application

There’s a big debate at the moment about how to support multiple platforms and devices, because as the pool of platforms increases, so does the knowledge required to code and build for these platforms. As software developers we don’t want to be building applications using different languages and APIs.

Watershed has begun to tackle this problem by adopting new web technologies such as HTML5 to built cross-platform applications using our own ‘Web Application Framework’. And, the new foyer screen application was an ideal candidate for this treatment.

The framework allowed us to rapidly prototype an app, within an afternoon, which simply read information from our ‘What’s On’ API and displayed it on the screen. However, the devil is always in the detail: changing the resolution, orientation, chipset or browser threw up loads of bugs. Ironing out all these problems and then deploying the app took time. However, there were some distinct advantages to using a web app approach:

  • jQuery enabled us to easily design our site to be responsive – adapting to the browser size, device orientation or resolution, with little code overheads.
  • HTML5 local storage enabled us to cache information on the page, so it didn’t have to be updated so often. This dramatically reduced page load times, enabling us to run the app on slower chipsets.
  • Web based apps can be updated centrally. This means we can update the app very quickly, and all the changes will appear across all devices automatically.

After some iterative development, refinement, testing, testing, testing, and last minute panic we deployed our foyer screen web app. And so far it’s not fallen over once!

Our What's On Today Foyer Screen Web App


Driving Display Screens using Raspberry Pis

For the uninitiated, Raspberry Pis are the coolest things since ever. No, really. Imagine a computer the size of a credit card – you’ve imagined a Raspberry Pi.

They were developed by the Raspberry Pi Foundation, with the intention of promoting the teaching of basic Computer Science in schools, and along with this they are increasingly being adopted by the technology world at large. At £30-ish each they are a cost and space effective way of delivering processor power, and perfect to replace our recently deceased foyer screen machine.

Desktop machine vs Raspberry Pi

Our old foyer screen machine had been driving five screens relentlessly for eight years, and over that time it had also accumulated an inordinate amount of dust. No wonder really that upon their post-mortem we discovered that the graphic card’s fans had spun apart, causing the heat sinks to melt off their chipsets.

A very broken graphics card

As a cost effective solution we replaced the old desktop with five new Raspberry Pis. Stewart, our systems administrator, masterminded their deployment.

Thanks to some black magic wizardry, Stewart programmed the Pis to load their disk image over NFS. This means we can bundle and update the Pis software in once place, centrally, and update them remotely. Also, because we don’t want the screens to run 24/7, the Pis automatically turn off when the building is closed.

Once booted, the Pis will launch Chrome Web Browser in full screen mode and load our new foyer screen web app. The app then makes the relevant API calls and renders our ‘What’s On’ data to the screen.

The Raspberry Pi is a brilliant solution for so many reasons. Not only are we support a brilliant foundation, but we are, ourselves, employing a low cost bare-bone solution, which is easy to maintain, space efficient and doesn’t gather dust!

Five Raspberry Pis Carefully Mounted and Serving our Display Screen

In Conclusion…

At Watershed we always take risks to produce solutions that are creative, cost effective and progressive. Our foyer screen system has coordinated so many different aspects of technology together, and it has been exciting to deploy systems using emerging web and hardware technologies. Developing this system has encouraged us to invest more in both Web Application development using HTML5 technologies and Raspberry Pi computers. And, as of yet, nothing has fallen over – or melted…

Written by Richard Grafton

Richard is Senior Developer at Watershed, where he supports and develops Watershed’s digital presence and programmes. Before working at Watershed, Richard was a research technologist at BBC R&D, and the Media Technology Lab at the University of Sussex. He holds a BSc (Hons) in Multimedia and Digital Systems.

One thought on “Building a low cost Foyer Screen System with Web Apps and Raspberry Pis

  1. Huzzah! Awsomeness!

    And with the formalities by, how do you do power management, specifically of the screens? You say the Raspis aren’t on 24/7, which sounds reasonable. I naïvely assume that the screens are on while the Raspberries are, and off while the Pies are asleep. Shutting the Pies down by cron is trivial enough, but how do you wake them up? Wake-On-LAN?


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