History of the PiPhone Kit (Part I)

>> For the latest on our PiPhone, see the PiPhone project page.

The Leimert Phone Company began with a simple question: “how can we use payphones to act as portals for local culture?” An early prototype considered how people might come to a local payphone to download local music in digital formats. This encouraged people to come visit a neighborhood to understand its music.

The advent of digital media all too often paves over local culture because people see technology as a one-size-fits-all solution. By comparison, we wanted to do urban planning within technology design. We needed a way to work with technology that provided a high degree of flexibility for civic hackers and community groups. We wanted a platform for culture.

payphone kit3

One of the interesting outcomes of the last year is a small PC board kit that costs $10, an early version of which is shown above. We call a payphone with a Raspberry Pi in it a “PiPhone.” It looks the same from the outside, but a PiPhone can do anything that a small internet server can, such as hosting web pages, taking pictures of visitors, and even delivering digital music locally as the community envisioned.

The kit helps answer questions such as: how can we use the knowledge we’ve obtained to make it easier to do this type of community design in the future? How might a kit ease the route from prototyping to broader implementation?

pi plus phone

We used a Raspberry Pi computer because it was low-cost ($25-35) and had the full features of a Linux server. This presented a challenge because these devices don’t naturally talk with one another. One is old and has an analog 25-pin plug that looks like an old printer cable, the other a new devices with a set of digital inputs and outputs that connects through a 26-pin ribbon cable. Figuring out how to connect these very different devices took some teamwork. To start with, we downloaded a lot of old documents, and did a hackathon to tinker with the insides and reverse engineer the hardware.



payphone kit1

Eventually we used breadboard – a way to create easily changeable test circuits – to get the Raspberry Pi to detect keypad entry and coin drops on the payphone.


The breadboard version evolved into a proto-board version where all the traces have been soldered to different components. This connected the two different technologies together and was more durable. But breadboard circuits still took a long time to assemble and test… and the traces had a tendency to flex and break!

payphone kit3

For a little over $100 we had 22 PC boards made up from the same circuit. While we are still working out the kinks in the design, these were even better because anybody who knew how to solder could assemble and test them in around 15 minutes. The days of flying wires flexing and breaking were over!




The PC board versions can be easily installed in a plastic project box with a Raspberry Pi then installed in a payphone. Now making prototypes a reality involves writing a few lines of software. The kit solves serious problems for scaling up, and lets us do community-centered design events involving payphones in a more widespread way.

How would you use a PiPhone? Do you have a particular payphone you want to convert? Let us know by tweeting at us on Twitter