I have a message for you…

If you’ve been in the UK this year and you ever pick up the newspaper or turn on the TV news, you’ll be aware that it’s Alan Turing’s centenary. It’s been a wonderful time to launch a project like Raspberry Pi; the Turing centenary, along with the 30th birthday celebrations for the BBC Micro and Spectrum, means that UK computer science, especially in schools, is something that the whole country has actually been paying attention to this year. (And now the Olympics are finished, we hope they’ll look back in this direction again.)

I got talking to Jonathan Hogg, from Output Arts, a small arts collective that has been making multisensory art installations since late 2009. This being the centenary year, they decided to take Turing’s work at Bletchley Park as a starting point for a commission they were given earlier in the year. And they used a Raspberry Pi to do it. Here are the results, and some commentary from Jonathan on the project. I very much hope we’ll be able to go and see I have a message for you… when it’s next on display; hearing what our little computer was doing in this piece made the hairs on the back of my neck prickle, and I really look forward to seeing what Output Arts do with their next Raspberry Pi.

A message for you

Earlier in the summer, Output Arts won a commission to work with Bletchley Park and Milton Keynes Museum to make an artwork on the theme of “communication” to be shown as part of the Milton Keynes Fringe Festival. Inspired by the work of Alan Turing, we decided to make a piece based on the Delilah speech scrambling system designed by Turing towards the end of the Second World War. The original design of the Delilah system consisted of a pseudo-random number generator and a modulo adder implemented entirely in analogue using valves. Working from the original technical report held at the National Archives in Kew, we wrote a digital simulation of the algorithms in a combination of Python, Cython and NumPy, tuned to run on a Raspberry Pi in realtime.

Mug, speakers, field telephone

The equipment of the piece consisted of a box with two knobs, two indicator lights and a hidden motion sensor. This was styled to try and make it look like an old piece of equipment, and was connected to an original WWII military field telephone loaned to us by Milton Keynes Museum. The equipment sat on an old table – also on loan from the museum – and this was placed within a small wooden hut, painted up to look something like a code-breaker hut that might have been found at Bletchley Park during the war. When the box senses motion, it makes the phone ring to encourage participants to lift the receiver. Picking up the receiver activates the system.

Interior view, including Raspberry Pi

We collected messages at Milton Keynes museum and Bletchley Park that were recorded and then scrambled using the Delilah simulation. These scrambled messages were stored as audio files on the SD card of the Pi and then descrambled for listening. The process was deliberately interfered with so that the messages being listened to slowly degrade in quality until they become just noise. The two knobs on the box control the volume of playback and one of the parameters of the descrambling, providing the participant with some sense of control over the listening process – although not enough to put off the eventual destruction of the message. An Arduino board connected to the Raspberry Pi by USB was used to interface with the knobs, lights and motion sensor, and the hook switch and ringer of the telephone; a small circuit connected to the Arduino switches 12V power for the ringer. We also used a USB audio output device as we experienced some distortion of the built-in audio output of the Raspberry Pi under load.

Raspberry Pi, veroboard

This is the first time we’ve used a RaspberryPi in an artwork, although we have been using Arduino boards for years. It’s been really exciting to be able to try out a Raspberry Pi and has opened up a lot of new possibilities in what we can do in small embedded pieces.

The artwork was shown from 19th to 29th July in the centre of Milton Keynes, and we are hoping to be able to show it again sometime soon, either in London or back in Milton Keynes. Output Arts are very grateful to the staff and volunteers at Bletchley Park and Milton Keynes Museum for their help with the piece.