# Project Context

This project implements a data acquisition (DAQ) system for an aquaponic farm: the *Ferme Aquaponique du Pays de Gex*, located in the Pays de Gex, France.

Website: https://www.lafermeaquaponique.com/

## Users

- Customers are aquaponic farmers.
- Assume no higher IT sophistication than the average person.
- Assume deep expertise in aquaponic farm design and operation.

## Architecture

All hosts are on the same farm LAN.

- 4 DAQ nodes: Raspberry Pi 2W units, each with 1 Atlas Scientific USB EZO carrier board + 1 probe
- 1 DAQ hub: Raspberry Pi 5 (MQTT broker)
- 1 DAQ recorder: remote VPS (persists MQTT messages to SQLite)
- 1 Dashboard: same VPS (Mojolicious web app)

Probes: pH, EC, Dissolved Oxygen, ORP (all Atlas Scientific).

## Messaging

- DAQ nodes publish readings over MQTT.
- DAQ hub acts as MQTT broker.
- DAQ recorder persists all MQTT messages to a relational database.
- Topics: `fapg/daq/<probe>/<node>/reading`
- Schema: `fapg.daq.reading.v1`
- Probe keys are always lowercase: `ph`, `do`, `orp`, `ec`.

## OS Versions

| Host         | OS                   | Version  |
|--------------|----------------------|----------|
| DAQ nodes    | Raspberry Pi OS Lite | Trixie   |
| DAQ hub      | Raspberry Pi OS Lite | Trixie   |
| DAQ recorder | Debian 11            | Bullseye |
| Dev machine  | Gentoo               | latest   |