van-tools

Monitoring and automation tools for the van build.

simarine/ — Pico UDP Monitor

Real-time monitor for the Simarine Pico battery/tank monitoring system. Listens for UDP broadcast packets, decodes sensor data, serves a JSON HTTP API, and logs to SQLite.

Hardware

• Simarine Pico rev.1 (fw 2.2.0.001) — main display unit
• SC303 shunt module (ID 3486) — battery voltage, current, SOC
• ST107 tank module (ID 8251) — water tank level (currently offline)
• 3×175W solar panels → Victron MPPT
• Sterling B2B 120A charger
• 20-gal water tank

How It Works

The Pico broadcasts 219-byte UDP packets on port 43210 every ~1 second. Each packet has a 14-byte header followed by repeating 7-byte sensor fields:

[field_nr] [0x01 type] [a_hi] [a_lo] [b_hi] [b_lo] [0xff sep]

Values a and b are unsigned 16-bit big-endian integers. The sensor map decodes known elements:

Element	Sensor	Decode	Unit
5	Pico internal voltage	b / 1000	V
14	House battery voltage (shunt)	b / 1000	V
15	Water tank resistance	raw b	Ω
26	House battery SOC	a / 160	%
28	House battery voltage (dup)	b / 1000	V
3	Barometric pressure	raw b	raw

Unknown elements are included as raw values in the API output for identification.

Installation

# Clone onto the Pi
git clone git@github.com:kirtr/van-tools.git
cd van-tools

# Install systemd service
sudo cp simarine/simarine.service /etc/systemd/system/
sudo systemctl daemon-reload
sudo systemctl enable --now simarine

Configuration

Environment variables (set in the service file or override):

Variable	Default	Description
UDP_PORT	43210	Pico UDP broadcast port
HTTP_PORT	8080	HTTP API listen port
LOG_INTERVAL_S	60	SQLite write interval (seconds)
DB_PATH	simarine.db	SQLite database file path

API

GET / — Current State

Returns the latest decoded sensor values plus all raw element data.

{
  "timestamp": 1710000000.0,
  "iso_time": "2025-03-09T12:00:00Z",
  "packet_count": 4200,
  "decoded": {
    "house_battery_voltage": {
      "value": 13.21,
      "unit": "V",
      "element": 14,
      "raw_a": 0,
      "raw_b": 13210,
      "description": "SC303 ch2 house battery voltage at shunt"
    },
    "house_battery_soc": {
      "value": 98.1,
      "unit": "%",
      "element": 26,
      "raw_a": 15696,
      "raw_b": 0,
      "description": "House battery state of charge"
    }
  },
  "raw_elements": {
    "0": {"a": 123, "b": 456},
    "5": {"a": 0, "b": 12340}
  }
}

GET /history?hours=24 — Historical Readings

Returns logged readings from the past N hours.

{
  "hours": 24,
  "count": 1440,
  "readings": [...]
}

GET /health — Health Check

{"status": "ok"}

Architecture

┌─────────────┐    UDP :43210     ┌──────────────────┐
│ Simarine Pico│ ─── broadcast ──→ │  monitor.py       │
└─────────────┘                   │                    │
                                  │  ┌─ udp_listener   │
                                  │  │  parse + decode  │
                                  │  │                  │
                                  │  ├─ http_server     │──→ JSON API :8080
                                  │  │                  │
                                  │  └─ db_logger       │──→ simarine.db (SQLite WAL)
                                  └──────────────────────┘

Three threads: UDP listener updates shared state, HTTP server reads it, DB logger snapshots it every 60s. SQLite uses WAL mode and NORMAL sync for SD card longevity.

Development

# Run locally (needs UDP packets or a test harness)
cd simarine
python3 monitor.py

# Check logs
journalctl -u simarine -f

Extending the Sensor Map

Edit sensor_map.py to add new elements as you identify them from the raw API output. Each entry maps an element ID to a name, unit, decode function, and which field (a or b) to use.