Interactive Core Memory Shield for Arduino Visualized using a FeatherWing LED Matrix

Magnetic-core memory was the go-to RAM platform for computer systems from the mid-’50s to the mid-’70s. Core uses tiny magnetic rings with interwoven wires (three per core) to read and write information, with each core storing 1-bit of data that can be switched from 0 to 1 based on the magnetic orientation. While core memory hasn’t been used in any significant or minor computer systems for over 40 years, some just love playing with retro tech, including Andy Geppert, who created an Interactive Core Memory Shield for Arduino.

For his build, Geppert expanded on Jussi Kilpelainen’s Core Memory Shield (features ferrite cores to store information), which he describes as a “hilariously impractical memory extension shield for your 3.3V / 5V Arduino.” After assembling the CMS kit, Geppert decided to take it to the next level by making it interactive so he could see the bits flipping in real-time. Since you can’t see magnetic field states, he needed a way to visualize the transitions and outfitted the Shield with an 8 x 8 LED matrix driven by a Rainbowduino Driver Platform that uses a simple serial protocol to update the LEDs.

After finding the platform worked well, Geppert pushed his project even further by ditching the 8 x 8 matrix and placing the LEDs next to each core, and illuminating them as a reflection of the core’s state in real-time. To get it to function correctly, he adapted an Adafruit FeatherWing 4 x 8 LED matrix board to the bottom side of the cores using a 3D-printed plastic adapter.

The LEDs are updated every 25 milliseconds, and illuminate as each core is touched using a stylus he built with a screwdriver with a magnet attached to its side, which focuses the magnetic field at its tip. You can follow Geppert’s complete build on his write-up here.