Rugged enclosure, power budget, radio link, and a firmware path that still boots when the weather disagrees.
Field nodes fail at the edges: connectors, condensation, brown-outs, and “it worked on the desk.” This build treated the enclosure and the board as one system — seal, thermal path, antenna keep-out, and service access.
On the electronics side: regulated power with brown-out handling, sensor front-end with known noise floor, and a conservative radio duty cycle. Firmware stayed boring on purpose — state machine, watchdog, structured logs, OTA only after the offline path was solid.
We validated outdoors with the same checklist we use for customer prototypes: cold start, link recovery, battery curve, and a tear-down after rain.