January 6, 2026
Air gap or just air cap?
Creating a Bespoke Data Diode for Air‑Gapped Networks
Raspberry Pi “one‑way wire” sparks an air‑gap fight — purists vs pragmatists
TLDR: A team used two Raspberry Pis and a one‑way light link to pull logs from an isolated network. Commenters erupted over whether that still counts as “air‑gapped,” if the build is robust, and whether a cut‑wire cable would suffice—practical monitoring vs purist security in one spicy debate.
A UK shop says it built a safe, one‑way “data diode” to pull health logs out of an air‑gapped network using two Raspberry Pi boards and a light‑based isolator. The pitch: reliability over speed, no back channel, just syslogs out. The comments? Oh, they lit up like a switchboard.
On one side, fans of practical fixes applauded the clever, low‑cost setup. On the other, security purists pounced. One critic dismissed the pictured build as a mere prototype, saying it “doesn’t look deployable.” Another waved a bargain‑bin alternative: just use an old‑school serial cable and literally snip the “talk back” wire. The biggest flame? The eternal debate over what “air‑gapped” even means. If data flows out, is it still an air gap—or just a one‑way door? Cue the semantic fireworks: “A ‘diode’ is not an air gap” became the rallying cry.
The maker jumped in, calmly offering to field tech questions and stressing one‑way only, slow‑and‑steady scripts, and audited reliability. Meanwhile, the peanut gallery delivered memes: “Schrödinger’s air gap,” “Pi‑pe dream,” and “TX‑pin diet” jokes. The vibe: pragmatists cheering a useful tool for monitoring critical systems, purists warning that connecting a full computer on the receiving end is a risk without deep audits. It’s the oldest internet fight: perfect vs done, with a side of cable‑cutting bravado and a dash of terminology turf war. Read the thread for the drama, stay for the snarky engineering hacks.
Key Points
- •Nelop Systems implemented a bespoke data diode to export syslog and performance data from an air-gapped network.
- •The system uses two Raspberry Pi devices linked via an opto coupler to ensure one-way, electrically isolated transmission.
- •Custom scripts prioritize reliability over speed to prevent data loss and avoid cross-contamination between networks.
- •Initial serial port testing was replaced by a UART interface for simpler, more reliable unidirectional communication.
- •The solution aims to maintain air-gap integrity while providing operational monitoring, supported by UK-based on-site service and 25+ years of experience.