Merge pull request #1499 from thomas7475/main

fix: Prevent NoneType error in async_read_serialnr in plugin_growatt.py

Author: wills106

custom_components/solax_modbus/plugin_growatt.py

@@ -62,7 +62,7 @@ async def async_read_serialnr(hub, address):
     res = None
     try:
         inverter_data = await hub.async_read_holding_registers(unit=hub._modbus_addr, address=address, count=5)
-        if not inverter_data.isError():
+        if inverter_data and not inverter_data.isError():
             decoder = BinaryPayloadDecoder.fromRegisters(inverter_data.registers, byteorder=Endian.BIG)
             res = decoder.decode_string(10).decode("ascii")
             hub.seriesnumber = res
@@ -2436,6 +2436,21 @@ def value_function_inverter_module(initval, descr, datadict):
         allowedtypes = GEN2 | GEN3 | GEN4,
         internal = True,
     ),
+    GrowattModbusSensorEntityDescription(
+        name="PV Isolation Resistance",
+        key="pv_isolation_resistance",
+        register=200,
+        register_type=REG_INPUT,
+        native_unit_of_measurement="kΩ",
+        state_class=SensorStateClass.MEASUREMENT,
+        # Register 200 is used to avoid a conflict with the 'BMS 1 Serial Number' 
+        # entity on some GEN4 hybrid models (e.g., TL-XH) which uses 3087.
+        # Confirmed working on GEN4 PV models (MIC 600TL-X).
+        allowedtypes=GEN2 | GEN3 | GEN4,
+        entity_category=EntityCategory.DIAGNOSTIC,
+        entity_registry_enabled_default=True,
+        icon="mdi:omega",
+    ),
 
     # Not documented, source: https://www.photovoltaikforum.com/thread/192228-growatt-sph-modbus-rtu-rj45-pinout-und-register-beschreibung/?postID=3017838#post3017838
     GrowattModbusSensorEntityDescription(