Software

Simulator

The whole stack on a laptop, with a carbonate-system model that produces realistic titration curves.

cd firmware/openreef_analyzer
./dev.sh                 # = python3 -m venv .venv && .venv/bin/pip install -e ".[dev]" && .venv/bin/openreef serve --sim --speedup 50

Open http://localhost:8080. Every button works; a “6-minute” alkalinity test finishes in about seven seconds at 50× speed.

What is modelled

Cell A holds total alkalinity and acid as absolute amounts; pH is solved from the charge balance TA = HCO₃⁻ + 2 CO₃²⁻ + OH⁻ − H⁺ with seawater K₁, K₂ and DIC ≈ 0.92 × TA. The resulting curve has the real inflection and the real Gran-region curvature, which is how the DIC-corrected fit was validated.
Cell B develops colour with first-order kinetics (τ = 150 s phosphate, 500 s nitrate) toward 0.47 A/ppm (PO₄) and 0.020 A/ppm (NO₃), with each dye’s spectral shape across the ten channels, LED spectra, dark counts and shot noise.
Fill, level and drain pumps move volume with ±0.4 % metering noise; overflow goes to a waste counter; dispenses are routed to the right cell by pump configuration.
Syringe pumps track plunger position, home switches and refills exactly as the real driver does.
Leak and waste-full conditions can be injected.

Changing the “tank”

curl -X POST localhost:8080/api/v1/sim/tank -H 'Content-Type: application/json' \
  -d '{"alk_dkh": 7.2, "po4_ppm": 0.18, "no3_ppm": 12, "leak": false}'

Tests

pytest -q

The suite runs five simulated chemistry scenarios (alkalinity recovery within 0.08 dKH, acid standardisation within 0.0003 N, two-point PO₄ and NO₃ calibrations then measurement, reagent accounting and event flow, leak abort) and three API scenarios (auth, the full REST surface, calibration endpoints) in about 30 seconds.

Using it for development

The Hardware base class in openreef/hal/base.py is the only contract. To support a different sensor or pump, subclass it (or RpiHardware) and point hardware.backend at your class. Procedures in openreef/sequences/procedures.py never touch GPIO directly, so a new procedure written against the simulator will run unchanged on the analyzer.