feat: add LAFVIN UPS Module 3S sensor plugin (lafvin_ups_3s)

Adds a new sensor type for the LAFVIN UPS Module 3S, an INA219-based
uninterruptible power supply for Raspberry Pi. Reports pack voltage,
current, power, estimated state-of-charge, and charge state for a
3S Li-ion/LiPo battery configuration (9.0–12.6 V range).

The INA219 address defaults to 0x41 (as wired on the LAFVIN board)
and shunt resistance is configurable for accurate current readings.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

repeater/sensors/lafvin_ups_3s.py

@@ -0,0 +1,159 @@
+"""
+LAFVIN UPS Module 3S battery monitor plug-in — INA219 at I2C 0x41.
+
+Reads a 3S lithium-ion/LiPo battery pack via INA219. Reports pack voltage,
+current, power, estimated state-of-charge, and charge state.
+
+The INA219 address is 0x41 by default (A0 bridged to VCC, A1 to GND on the
+LAFVIN board) but is configurable for boards wired differently.
+
+Requires: pip install smbus2
+
+Config example:
+  - type: lafvin_ups_3s
+    name: "battery"
+    enabled: true
+    auto_install_packages: false
+    settings:
+      i2c_address: 0x41   # Default LAFVIN UPS 3S address
+      bus_number: 1        # I2C bus (1 for Raspberry Pi default)
+      shunt_ohms: 0.1      # Shunt resistor value in ohms
+      max_amps: 5.0        # Maximum expected current in amps
+"""
+
+from __future__ import annotations
+
+import time
+from typing import Any, Dict, Optional
+
+from .base import SensorBase
+from .registry import SensorRegistry
+
+# INA219 register addresses
+_REG_CONFIG      = 0x00
+_REG_SHUNT       = 0x01
+_REG_BUS         = 0x02
+_REG_POWER       = 0x03
+_REG_CURRENT     = 0x04
+_REG_CALIBRATION = 0x05
+
+# 32V range, ±320mV shunt gain, 12-bit ADC, continuous shunt+bus
+_CONFIG_VALUE = 0x399F
+
+# 3S LiPo/Li-ion pack voltage thresholds (3 cells in series)
+_V_MAX  = 12.6   # 4.20 V/cell × 3 — fully charged
+_V_MIN  =  9.0   # 3.00 V/cell × 3 — cutoff
+
+
+def _pack_voltage_to_percent(v: float) -> int:
+    """Piecewise linear SoC estimate for a 3S Li-ion/LiPo pack (9.0–12.6 V)."""
+    cell = v / 3.0
+    if cell >= 4.20: return 100
+    if cell >= 4.00: return int(85 + (cell - 4.00) / 0.20 * 15)
+    if cell >= 3.80: return int(60 + (cell - 3.80) / 0.20 * 25)
+    if cell >= 3.70: return int(40 + (cell - 3.70) / 0.10 * 20)
+    if cell >= 3.50: return int(15 + (cell - 3.50) / 0.20 * 25)
+    if cell >= 3.00: return int(       (cell - 3.00) / 0.50 * 15)
+    return 0
+
+
+@SensorRegistry.register("lafvin_ups_3s")
+class LafvinUps3sSensor(SensorBase):
+    sensor_type = "lafvin_ups_3s"
+
+    def __init__(self, name: str, config: Optional[Dict[str, Any]] = None, log=None):
+        super().__init__(name=name, config=config, log=log)
+
+        addr = self.settings.get("i2c_address", 0x41)
+        self.i2c_address  = int(addr, 0) if isinstance(addr, str) else int(addr)
+        self.bus_number   = int(self.settings.get("bus_number", 1))
+        self.shunt_ohms   = float(self.settings.get("shunt_ohms", 0.1))
+        self.max_amps     = float(self.settings.get("max_amps", 5.0))
+
+        # INA219 calibration per datasheet
+        self.current_lsb  = self.max_amps / 32768.0
+        cal               = int(0.04096 / (self.current_lsb * self.shunt_ohms))
+        self.calibration  = max(1, min(cal, 0xFFFF))
+        self.power_lsb    = self.current_lsb * 20.0
+
+        self.available = False
+
+        if not self.ensure_python_modules([("smbus2", "smbus2")]):
+            return
+
+        try:
+            import smbus2  # type: ignore[import-not-found]
+            self._smbus2 = smbus2
+
+            bus = smbus2.SMBus(self.bus_number)
+            try:
+                self._write(bus, _REG_CONFIG, _CONFIG_VALUE)
+                self._write(bus, _REG_CALIBRATION, self.calibration)
+                time.sleep(0.15)
+            finally:
+                bus.close()
+
+            self.available = True
+            self.log.info(
+                "LAFVIN UPS 3S INA219 initialized (addr=0x%02X, bus=%d, shunt=%.3fΩ)",
+                self.i2c_address,
+                self.bus_number,
+                self.shunt_ohms,
+            )
+        except Exception as exc:
+            self.log.warning(
+                "LAFVIN UPS 3S init failed (addr=0x%02X, bus=%d): %s",
+                self.i2c_address,
+                self.bus_number,
+                exc,
+            )
+
+    def _write(self, bus, reg: int, val: int) -> None:
+        bus.write_i2c_block_data(
+            self.i2c_address, reg, [(val >> 8) & 0xFF, val & 0xFF]
+        )
+
+    def _read_u(self, bus, reg: int) -> int:
+        d = bus.read_i2c_block_data(self.i2c_address, reg, 2)
+        return (d[0] << 8) | d[1]
+
+    def _read_s(self, bus, reg: int) -> int:
+        v = self._read_u(bus, reg)
+        return v - 0x10000 if v & 0x8000 else v
+
+    def _read(self) -> Dict[str, Any]:
+        """Read voltage, current, power, and derived battery state."""
+        if not self.available:
+            raise RuntimeError("LAFVIN UPS 3S not available")
+
+        try:
+            bus = self._smbus2.SMBus(self.bus_number)
+            try:
+                self._write(bus, _REG_CALIBRATION, self.calibration)
+
+                bus_v      = (self._read_u(bus, _REG_BUS) >> 3) * 4 / 1000.0
+                shunt_mv   = self._read_s(bus, _REG_SHUNT) * 0.01
+                current_ma = self._read_s(bus, _REG_CURRENT) * self.current_lsb * 1000.0
+                power_mw   = self._read_u(bus, _REG_POWER) * self.power_lsb * 1000.0
+            finally:
+                bus.close()
+
+            pct = _pack_voltage_to_percent(bus_v)
+
+            if current_ma < -50:
+                state = "charging"
+            elif current_ma > 50:
+                state = "discharging"
+            else:
+                state = "idle"
+
+            return {
+                "bus_voltage_v":    round(bus_v, 3),
+                "shunt_voltage_mv": round(shunt_mv, 2),
+                "current_ma":       round(current_ma, 1),
+                "power_mw":         round(power_mw, 1),
+                "battery_percent":  pct,
+                "charge_state":     state,
+            }
+        except Exception as exc:
+            raise RuntimeError(f"LAFVIN UPS 3S read failed: {exc}") from exc