Outdoor Meshtastic Soil Sensor Prototype

I need two simple yet reliable prototype nodes that can sit outdoors, wake up at a configurable interval, pull a register line from a Modbus-compatible soil probe, and push that reading through a Meshtastic link. No commercial polish required—the goal is to prove the data path end-to-end.

Scope of work
• Recommend and source—or at least specify—a compact board, radio module, and battery pack (AA-powered) suited for outdoor use. I currently have no hardware on hand, so component guidance is essential.
• Write Python-based firmware (preferred language) that:
– Powers the Modbus interface, retrieves the probe value, and sleeps between cycles to conserve the batteries.
– Publishes the reading over Meshtastic in a lightweight JSON or CSV payload.
• Use the Official Meshtastic CLI + Bash + Simple Script (Minimal Python) for my laptop to listen to a connected Meshtastic node, parse incoming packets, and insert each reading into an existing MySQL table with a timestamp.

Success criteria
• Both field nodes run for at least several days on fresh AAs while sending test readings every 15 minutes.
• The receiver script reliably captures and stores those readings in MySQL without manual intervention.
• All code, wiring diagrams, and a concise bill of materials are handed over so I can reproduce or iterate on the build.

Speed matters more than aesthetics; if it works, I’m happy.