Metro beat

Metro Beat

To make the public transportation playful and entertaining for its commuters. And as part of the “Gaming the System” art exhibition, a public transportation ticket validator machine was hacked into a music sampling apparatus.


The making

The first prototype was built using openFrameworks. The prototype helped the process of getting a card validator machine from the Helsinki Public Transportation. 

It was not possible to have access to the technical data sheet. Instead, we hacked our way by using a Raspberry Pi 2 (RPi), an Arduino Micro, 5 volt light bulbs, a USB virtual 7.1 sound adapter But, and the machine original LCD.


The USB Sound Card

Making the sound card work was challenging. We were using a basic button microphone as our input and a regular speaker. The sound card was directly connected to the RPi 2, via the USB connector.

The finding was that the USB speed for writing and reading should be the same. The sound card speed,  was 1.1 and the RPi speed was 1.0 and that was causing the playback with distortions and in some cases crashing the system. Couple lines of code were the solution to adjusted our write and read speed.


Installing PD on RPi

We were using Pure Data (Pd) as our programming language. To run the patch we had to install it on the RPi. Even though there are online tutorials, but having background knowledge in Linux can be an advantage which we did not have.

Our first attempt was a failure. Eventually, we had to reinstall the OS and install the software again by formatting the RPi. It is important to follow the command accordingly and have a clean installation. The errors were caused by the incorrect order of command.


The Buttons

To have full control over the buttons was to carve out the thick layer of silicon. It was not an easy task, as it requires special tools. Also, that fact that we had to return back the machine with the least damages.

Eventually, the button wires soldered to the Arduino.


Assembling The Machine

Each time we assemble the machine its functionality would change as the sensors were too sensitive. Each screw was affecting the sensitivity of the buttons.

Fewer screws and different stationary materials, such as a cardboard and napkins were the solutions to the sensitivity of the machine buttons. And also, 3M electrical tapes and papers were wrapped around the components.



Gaming the System is an international art exhibition produced by the research team “These Animals” together with the cultural production, Taidelinja, the Aalto University School of Art and Design and the Pixelache festival. A project for the celebration of the 70th anniversary of the public transportation in Helsinki

This project was granted 400 euros from its partnering organization, Aalto ARTS.


Team: Niklas Pöllönen and Fernando Visockis.

Acknowledgement: Matti Niinimäki and Ali Neissi

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