HEARD

Safety gear is built for individuals. Accidents happen to groups.

Personal locator beacons and phone apps protect one person and assume a network. On a real trail a school group, a guided trek, a family what actually goes wrong is that someone drifts off the path, falls behind, and nobody notices until it is too late. Out where the cell towers stop, there is no tool that keeps the whole group aware of each other.

HEARD started as a Computer Engineering bachelor's thesis at the University of Bologna (2024–2025, supervised by Prof. Alessandro Ricci) and is now a fully open-source project. The goal: a cheap, rugged, build-it-yourself device that any hiking group can carry so the guide always knows where everyone is and anyone can call for help with one button.

A self-healing mesh that watches the route

Every hiker carries a GPS + LoRa device. A pre-loaded GPX route defines a corridor (±100 m by default). Each device continuously classifies its position as IN_PATH or OUT_PATH. The guide's device (the Core) polls the group; anyone out of direct radio range is reached through multi-hop relaying by the devices in between.

Off-the-shelf parts, one custom enclosure

The prototype is deliberately built from common, cheap modules so anyone can source and assemble it. An ESP32 runs the FreeRTOS firmware; a u-blox NEO-6M handles GPS; a LoRa transceiver does the long-range link; and the Core adds a 2.9" e-ink display that sips power and stays readable in direct sun.

Everything lives inside a 3D-printed case designed around the Waveshare e-paper module — the STL files for the Core enclosure are published as a release on GitHub.

Download enclosure STLs

// heard core — internals, coin for scale

Bill of materials (Core)

Three devices, one mesh

// industrial-design renders — core & pico

// guarded sos button — no accidental triggers (only concept)

How to build

HEARD is meant to be reproduced, not just admired. Even if we are working also on a "out of the box ready" solution the project is already easy to recreate. Here is the path from a cloned repo to a device in your pocket. Everything you need is in the GitHub repository, or watch the build on YouTube.

Print the enclosure

Grab the Core enclosure STLs from the GitHub release and print them. They're designed for the 2.9" e-paper module — no supports needed for most parts.

Wire up the electronics (working on a PCB with all the components included)

Source the parts from the BOM above and follow the reference wiring. The breadboard schematic is published as a Wokwi project, so you can see better all the connections.

Flash the firmware (Browser flasher will come)

The firmware is a PlatformIO project. Clone, open the code/core environment and upload — FreeRTOS handles GPS, radio and display tasks for you.

git clone https://github.com/luciobaiocchi/heard
cd heard/code/core
pio run -t upload        # build & flash the Core firmware
pio device monitor       # watch it acquire a GPS fix

Load a route & hike (working on a bluetooth loading)

Use the path_loader utility to push a GPX track over serial. Power on, wait for a fix, and the Core starts tracking the group against the route. That's it — you're off-grid and accounted for.

A digital twin of the whole mesh

You don't need a mountain to develop HEARD. The repo ships a simulator that compiles the actual firmware protocol code (the ConnectionManager) into a Python module via pybind11, then runs it tick-by-tick along real GPX tracks.

The channel model includes distance-based signal falloff and optional terrain line-of-sight using ITU-R P.526 knife-edge diffraction over real elevation tiles. A browser-based 3D replay viewer (MapLibre GL JS) plays back recorded runs on terrain — planned route, deviation corridor, device positions, LoRa transmission rings, live protocol state, delivery metrics and connectivity matrices. It's the same code you flash, validated in software first.

Open milestones

Tech stack

⚠ HEARD is a research prototype, not a certified safety device. Don't rely on it as your only means of rescue.