LORASOS

Maxwell SOS

Emergency comms for the mountains.
Solar-powered, long-range LoRa mesh that carries a hiker's distress call across cellular-dark terrain — straight to Mountain Rescue.

What is Maxwell SOS

A long-range, low-power radio mesh that carries a hiker's distress call across terrain with no cellular coverage — delivered directly to a mountain rescue station over LoRa. No GSM. No internet.

How it works

1. The hiker presses SOS. A small wearable sends a low-power radio call for help.
2. Repeaters relay the signal. Solar-powered stations on the slopes hop the SOS from peak to peak.
3. Mountain Rescue receives it. Delivered straight to the rescue station over LoRa.

Satellite fallback: only one repeater in the mesh needs a satellite module — it provides an uplink for the entire network.

Why a separate project (vs. Meshtastic)?

Meshtastic is a great general-purpose LoRa mesh — text chat, position sharing, telemetry, channels, encryption, MQTT bridging, phone pairing. That generality is the whole point of it, but it also means the protocol carries a lot of machinery an emergency beacon never needs.

Maxwell SOS does exactly one thing: get a distress call + GPS fix out, reliably, on the worst day. Stripping everything an SOS doesn't need lets us optimize hard for that:

• One message type, not a chat stack. No channels, telemetry, or app pairing — a tiny fixed SOS frame means shorter airtime, higher spreading factors, and more range per hop.
• Purpose-built repeaters. Solar, always-on, mounted on the slopes to relay the SOS peak-to-peak — not a hiker's phone-tethered node.
• Delivery to a rescue station, not a group chat. The mesh terminates at a Mountain Rescue endpoint.
• Satellite fallback by design. One repeater with a sat module uplinks the entire mesh where no ground path exists.

You could bolt an SOS onto Meshtastic — but you'd drag its whole feature set along to do it. Maxwell starts from the emergency case and builds only that.

Hardware

Core of the beacon / repeater node:

Bare PCB — rev. A, as received from fab

Assembled — hand-soldered first article

Core of the beacon / repeater node:

• Radio + MCU — RAK3172 (STM32WL): LoRa transceiver with integrated MCU
• GNSS — u-blox SAM-M10Q: position fix for the distress call
• Solar charging — TI BQ25185: LiFePO4 charge management
• Power — TPS631010 buck-boost + LiFePO4 cell
• Auto-SOS trigger — motion / inactivity detection via an IMU finite-state machine

Full bill of materials lives in hardware/.

Repository structure

MAXWELLS0S/
├── assets/                 logo, renders, photos
├── docs/                   documentation
├── hardware/               KiCad sources, schematic, BOM
│   └── WEARBALE-DEVICE/    wearable beacon (schematic + README)
├── protocol/               mesh protocol specification
├── .gitignore
├── LICENSE
└── README.md

Status

✅ Hardware design done — now in testing. The beacon schematic is complete and under bench testing. Detailed test results, firmware and full documentation are coming a bit later.

Roadmap

• Wearable beacon — schematic complete, in bench testing
• Relay / gateway node — hardware design
• Firmware — SOS frame, mesh relay, low-power sleep
• Field test — multi-hop range + solar endurance
• Satellite uplink module
• Rescue-station receiver

⚠️ Safety disclaimer

Maxwell SOS is an experimental, open-source project. It is not a certified safety device and does not replace a PLB/EPIRB on 406 MHz (COSPAS–SARSAT). A LoRa mesh does not guarantee message delivery — it depends on repeaters being in range. Never rely on this device as your only means of rescue. You are responsible for complying with local ISM-band regulations (EU868 / US915 / etc.).

License

Hardware design files are licensed under CERN-OHL-S v2 (strongly reciprocal). See LICENSE.

_{RESILIENCE FIRST}