Off-Grid Backhaul¶

For sensors out of WiFi range, compact serial lines ride a LoRa mesh to the base. Two stacks are supported today; the sensor firmware is identical for both (OUTPUT_SERIAL 1, plain text lines).

Meshtastic¶

ESP32 sensor ──serial──▶ field Meshtastic node ──LoRa──▶ base node ──USB──▶ serial_bridge ─▶ MQTT

1. Sensor: build the sketch with OUTPUT_SERIAL 1; it prints one compact line per event to its UART.

2. Field mesh node: wire the ESP32's TX to the node's RX (shared ground) and enable the Serial module in text mode:

   meshtastic --set serial.enabled true --set serial.mode TEXTMSG \
              --set serial.baud BAUD_115200
   

3. Base mesh node: a Meshtastic node on USB to the Pi receives the messages.

4. Bridge: python -m mqtt.serial_bridge --serial-port /dev/ttyUSB0 [--sensor-map config/sensor_nodes.json] expands each line and republishes full JSON to the broker. The same bridge also ingests Detection Sensor module packets (contact sensors) and flags mesh-node presence.

MeshCore¶

Build the sensor sketches with SERIAL_MESHCORE 1; each line is framed in MeshCore's companion serial protocol as a channel message, prefixed NODE_ID: (MeshCore channel messages carry no sender id), for a wired MeshCore companion node such as a Heltec V3. At the base:

pip install meshcore
python -m mqtt.meshcore_bridge --serial-port /dev/ttyUSB0 --broker-port 1883

The bridge listens on a companion radio sharing the same channel and maps the prefixed lines to the standard MQTT payloads. Sensor and base radios must share the channel key; MESHCORE_CHANNEL in the sketch picks the channel index.

LXMF / Reticulum¶

Sensors reach a Reticulum network through a small relay host (a Pi Zero W with an RNode works) instead of a wired mesh node:

ESP32 sensor ──serial──▶ relay host (rns_field_relay) ──LXMF/RNS──▶ base (rns_bridge) ─▶ MQTT

The base side prints its LXMF destination hash on startup:

pip install rns lxmf
python -m mqtt.rns_bridge --broker-port 1883

The field side reads the unmodified sensor's serial lines and sends each as an LXMF message, prefixed with the node name:

pip install rns lxmf pyserial
python -m sensors.rns_field_relay --serial-port /dev/ttyACM0 \
    --dest <hash printed by rns_bridge> --node-name gate

Reticulum interfaces (RNode, TCP tunnels, ...) come from each host's own RNS config (~/.reticulum).

Off-grid alerts (RelayFabric)¶

ntfy, webhook, Twilio, and SMTP all need the Internet, the opposite of the remote sites this is built for. Set EnableMqtt = true in [Notifications] and the monitor publishes each alert as JSON to MqttAlertTopic on the same broker. RelayFabric subscribes there and relays alerts over a LoRa mesh (Meshtastic, MeshCore, or LXMF/Reticulum), so they reach you with no cellular. See RelayFabric's meshtripwire plugin (formatted alerts) or its examples/meshtripwire.yaml (generic mqtt plugin, no extra code).