Enhance helper functions for register value manipulation

- Added `make_32bit` and `split_to_16bit` functions to facilitate conversion between 16-bit and 32-bit register values using struct packing.
- Updated `value_to_reg` method in `NumberRWSensor` to utilize `split_to_16bit` for handling two 16-bit addresses.
- Modified `reg_to_value` method in `Sensor` class to use `make_32bit` for combining two 16-bit registers into a single 32-bit value, improving support for signed values.

src/sunsynk/helpers.py

@@ -2,7 +2,8 @@
 
 import logging
 import math
-from typing import Any
+from typing import Any, Tuple
+import struct
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -49,13 +50,20 @@ def as_num(val: ValType) -> float | int:
 
 
 def signed(val: int | float, bits: int = 16) -> int | float:
-    """Convert value to signed int."""
+    """Convert value to signed int using struct packing."""
+    if isinstance(val, float):
+        return val
+
+    if bits == 16:
+        return struct.unpack('h', struct.pack('H', val))[0]
+    if bits == 32:
+        return struct.unpack('i', struct.pack('I', val))[0]
+
+    # Fallback for non-standard bit lengths
     sign_bit = 1 << (bits - 1)
     if val < sign_bit:
         return val
     return val - (1 << bits)
-    # 16-bit only (old)
-    # return val if val <= 0x7FFF else val - 0x10000
 
 
 def slug(name: str) -> str:
@@ -125,3 +133,15 @@ def hex_str(regs: RegType, address: RegType | None = None) -> str:
     if address:
         res = (f"{k}={v}" for k, v in zip(address, res, strict=True))
     return f"{{{' '.join(res)}}}"
+
+
+def make_32bit(low16_value: int, high16_value: int, signed: bool = True) -> int:
+    """Convert two 16-bit registers into a 32-bit value using struct packing."""
+    fmt = '<i' if signed else '<I'
+    return struct.unpack(fmt, struct.pack('<2H', low16_value, high16_value))[0]
+
+
+def split_to_16bit(value: int, signed: bool = True) -> Tuple[int, int]:
+    """Split a 32-bit value into two 16-bit values using struct unpacking."""
+    fmt = '<i' if signed else '<I'
+    return struct.unpack('<2H', struct.pack(fmt, value))

src/sunsynk/rwsensors.py

@@ -9,7 +9,7 @@
 import attrs
 from mqtt_entity.utils import BOOL_OFF, BOOL_ON
 
-from sunsynk.helpers import NumType, RegType, SSTime, ValType, as_num, hex_str
+from sunsynk.helpers import NumType, RegType, SSTime, ValType, as_num, hex_str, split_to_16bit
 from sunsynk.sensors import Sensor
 
 _LOGGER = logging.getLogger(__name__)
@@ -68,17 +68,19 @@ def dependencies(self) -> list[Sensor]:
         return [s for s in (self.min, self.max) if isinstance(s, Sensor)]
 
     def value_to_reg(self, value: ValType, resolve: ResolveType) -> RegType:
-        """Get the reg value from a display value, or the current reg value if out of range."""
+        """Get the reg value from a display value."""
         fval = float(value)  # type:ignore
         minv = resolve_num(resolve, self.min, 0)
         maxv = resolve_num(resolve, self.max, 100)
         val = int(max(minv, min(maxv, fval)) / abs(self.factor))
+
         if len(self.address) == 1:
             if val < 0:
                 val = 0x10000 + val
             return self.reg(val)
         if len(self.address) == 2:
-            return self.reg(val & 0xFFFF, int(val >> 16))
+            low, high = split_to_16bit(val, signed=self.factor < 0)
+            return self.reg(low, high)
         raise NotImplementedError(f"Address length not supported: {self.address}")
 
 

src/sunsynk/sensors.py

@@ -14,6 +14,7 @@
     int_round,
     signed,
     slug,
+    make_32bit,
 )
 
 _LOGGER = logging.getLogger(__name__)
@@ -38,11 +39,15 @@ def id(self) -> str:
     def reg_to_value(self, regs: RegType) -> ValType:
         """Return the value from the registers."""
         regs = self.masked(regs)
-        val: NumType = regs[0]
-        if len(regs) > 1:
-            val += regs[1] << 16
-        if self.factor < 0:  # Indicates this register is signed
-            val = signed(val, bits=16 * len(regs))
+        if len(regs) == 1:
+            val = regs[0]
+            if self.factor < 0:  # Indicates this register is signed
+                val = signed(val, bits=16)
+        elif len(regs) == 2:
+            val = make_32bit(regs[0], regs[1], signed=self.factor < 0)
+        else:
+            raise ValueError(f"Unsupported register length: {len(regs)}")
+
         val = int_round(val * abs(self.factor))
         _LOGGER.debug("%s=%s%s %s", self.id, val, self.unit, regs)
         return val