GRIDNET — Communication That Works When Everything Else Fails

What If Your Power Outlet Was Also Your Network?

Every year, millions of people get cut off from communication. Earthquakes. Floods. Major infrastructure failures. The internet goes down. Cell towers go down. People can't reach their neighbors one block away.

But in most of these scenarios, one thing survives: the physical power line infrastructure. The wires are still there.

GRIDNET turns that infrastructure into a communication network.

It's an open hardware mesh terminal that sends messages over existing power lines using PLC (Power Line Communication) technology. No internet. No cell towers. No central servers. No accounts. And when the grid itself goes down, an onboard inverter keeps the signal alive on the wire.

How It Works

GRIDNET operates on three communication channels, automatically switching based on conditions:

1. Powerline (Normal Mode) The ST7580 PLC SoC injects OFDM signals onto the power line in the CENELEC EN50065 A-band (9–148 kHz). Every device acts as a repeater. Messages propagate across the neighborhood through your building transformer and beyond.

2. Inverter Mode (Grid Failure) When grid power fails, the onboard inverter circuit injects 24V AC onto the wire — just enough for PLC signaling, safe for all connected equipment. A master selection protocol ensures only one device injects at a time, preventing voltage conflicts.

3. Wi-Fi Mesh Fallback If the physical wire is damaged, the ESP32-C3 automatically activates Wi-Fi mesh mode. The separate PLC adapter also connects to the terminal wirelessly — so you can use the terminal anywhere in your home without cables.

Hardware Overview

The system has two units:

Terminal — ThinkPad-inspired clamshell form factor.

GD32VF103 processor (RISC-V, 108MHz)
ESP32-C3 (Wi-Fi mesh + Bluetooth 5.0 LE)
5.0" STN LCD, 800×480, amber backlight
40-key mechanical keyboard (Kailh LP) with amber backlight and red TrackPoint
4×4 numeric keypad + 4 programmable macro keys
Built-in speaker + microSD slot
8000mAh battery, ~6 days active use
260×160×28mm, ~680g

PLC Adapter — separate compact unit that plugs directly into any wall outlet. Connects to the terminal over Wi-Fi. Replaceable independently if it fails.

Prototype BOM: ~$112 USD

A Platform, Not Just a Device

Users write and share applications in a sandboxed Forth VM. Apps are distributed peer-to-peer over the network — like the BBS days.

A neighborhood shop can write its own order system. Two neighbors can play a turn-based strategy game. Someone can broadcast an emergency alert. All without internet, all without a server, all running locally on a 32KB-RAM microcontroller.

Here's a neighborhood market app in ~15 lines of Forth:

: HEADER  0 0 " ╔═══════════════╗" WRITE  0 1 " ║  CORNER SHOP  ║" WRITE  0 2 " ╚═══════════════╝" WRITE ;

: ORDER  HEADER  0 4 " 1. Bread  2. Milk" WRITE  KEY? SEND-MSG ;

: MAIN BEGIN ORDER 1000 WAIT AGAIN ;
MAIN

Safety First

GRIDNET's 24V AC injection is safe for all connected equipment and compliant with CENELEC EN50065:

Household devices operate at 230V / 50Hz — 24V is irrelevant to their power circuits
PLC signals at 9–148 kHz are naturally filtered by all consumer electronics
Max injected current: 100mA (household breakers trip at 16A)
24V AC is below the 50V SELV threshold per IEC 60479 — safe for humans
Galvanic isolation via transformer is mandatory and non-negotiable

This is the same principle HomePlug adapters have been using for 20+ years in millions of homes.

Full analysis: docs/electrical-safety.md

Project Status

Design stage is complete. All documentation, hardware architecture, protocol stack, and software design are published on GitHub.

✅ Dual-board hardware architecture (PLC/Power + Main Board) ✅ Full bill of materials and PCB layout plan ✅ Complete communication protocol stack (framing, mesh routing, ACK, store-forward) ✅ Inverter master protocol (prevents voltage conflicts during grid-down) ✅ Three-layer protection circuit design (TVS + MOV + relay + V-sense) ✅ Software architecture (Zephyr RTOS + Forth VM + firmware update) ✅ Enclosure design and mechanical specifications ✅ CENELEC EN50065 compliance analysis

Next: PCB prototype fabrication.

Looking For Collaborators

This is where I'm stuck alone. I need people.

Hardware engineer with embedded systems / PCB design experience
Anyone with real-world ST7580 or PLC field experience
Zephyr RTOS developers (RISC-V BSP, driver development)
Forth enthusiasts to help design the VM standard library
Beta testers willing to run a node in their building

If any of this speaks to you, open an issue on GitHub, leave a comment here, or reach out directly.

Inspiration

GRIDNET stands on three shoulders:

Minitel — France's pre-web national terminal network. A whole country connected, locally, before the internet existed.

FidoNet — A global decentralized BBS built by hobbyists. Store-and-forward over phone lines. No servers. No company. Just mutual agreement among nodes.

ThinkPad — A design philosophy: every detail intentional, built to last, keyboard first.

The slowness is intentional. The locality is intentional. The text-only interface is intentional. There's something worth preserving in a message that takes a few seconds to arrive from the next building.

Project Details