Communications & Connectivity
The open-source aisle: communications you own outright — open firmware on the radios, open programs on the boxes between, and no layer of it rented. For the general tour of every path a reading can take, the communications library is the guide; this aisle stocks the options whose software is yours.
LoRa Mesh Radio (915 MHz)
LoRa is a long-range, low-power radio that trades speed for distance: tiny messages, sent slowly on the license-free 915 MHz band, carry for miles on almost no power. Put LoRa radios in a mesh — every node relaying for the others — and you get off-grid text between vehicles, buildings, and hands, with no tower, no SIM, and no bill. Meshtastic, the well-known open-source firmware, is what runs it; the kits come pre-loaded.
OpenWrt: the Open Router
The open program for the router: the one load-bearing box every install rides on. On a supported model it replaces the factory firmware with one that keeps getting patched years after the maker moves on, and it unlocks what a farm actually wants from that box — a fenced-off network for the sensor fleet, real control of the radios, honest visibility into what is talking. The ISP's rental becomes yours the way an OAT board is yours.
WireGuard: the Door Home
A VPN (virtual private network) done the modern, open way: an encrypted tunnel from your phone to the farm's router, so that standing in town you are, for practical purposes, standing on the farm's network — dashboards and cameras reachable, nothing exposed to the public internet, no relay service rented. Small, fast, and already built into OpenWrt and Home Assistant.
Mosquitto: the Open MQTT Broker
MQTT is the sensor world's post office: boards publish each reading to a named topic ("barn/cooler/temperature") and anything you run subscribes to the topics it wants — one reading in, any number of listeners out. Mosquitto is the small, quiet, open broker in the middle: proven for years on the world's sensor traffic, and happy on any endpoint server, down to a Raspberry Pi.
RS-485 + Modbus: the Open Wire
The pair that wires professional instruments, both open standards older than the web. RS-485 is two wires built for hard places: a signal that carries hundreds of meters past the pumps and motors that would drown anything gentler. Modbus is the plain language industrial gear speaks over it — charge controllers, irrigation equipment, weather stations — and our open Modbus reader is the program that asks the questions and lands the answers at your endpoint.
OPNsense: the Open Firewall
For the farm that has become a campus: an open firewall and gateway running on a box you own, standing at the seam between the property and the world. Routing, rules, and a clear view of the traffic — none of it licensed per seat, per user, or per year.
Own the boxes between
Follow a reading home — off the radio, down the wire, through the router, into the record — and every box it passes is on this shelf, with an open program available for it. Flash it, run it, keep it, the way you keep an OAT board.
Honest tense, as always: OpenWrt runs on supported hardware, not every router (check the device list first), and nothing in this book requires any of it — factory firmware runs most farms fine. This is the ownership upgrade, not the entry fee.