Garage hardware runs unattended for months. Rare hangs. Ethernet driver stalls, memory fragmentation, or sensor bus lockups: are cheaper to recover with a watchdog reset than with a ladder trip. A timed reset reboots the MCU and reinitializes shields and sensors.
When watchdog helps
- Network stack freeze after router power blips.
- Infinite retry loop on a disconnected DHT22 data line.
- HTTP client backlog on the W5100 after sustained polling from the cloud.
Implementation notes
Pet the watchdog only when the main loop completes a full cycle: sensor read, LCD update, and HTTP housekeeping. Too-aggressive petting masks real deadlocks. Pair with DHCP renew and JSON serving logic in sketch polling main loop.
Operational expectations
Expect a brief JSON outage during reboot: seconds, not minutes. Stale reading debug distinguishes reboot gaps from feed misconfiguration. Ethernet stacking notes: Ethernet shield stacking.