Handle signed integers in handle_cmd_heartbeat properly (#62)

toshiba_ac/device/__init__.py

@@ -16,6 +16,7 @@
 
 import asyncio
 import logging
+import struct
 import typing as t
 from dataclasses import dataclass
 
@@ -129,7 +130,8 @@ async def handle_cmd_fcu_from_ac(self, payload: dict[str, JSONSerializable]) ->
             await self.state_changed()
 
     async def handle_cmd_heartbeat(self, payload: dict[str, t.Any]) -> None:
-        hb_data = {k: int(v, base=16) for k, v in payload.items()}
+        # Use signed conversion for temperatures, unsigned otherwise.
+        hb_data = {k: struct.unpack("b" if "Temp" in k else "B", bytes.fromhex(v))[0] for k, v in payload.items()}
         logger.debug(f"[{self.name}] AC heartbeat from AMQP: {hb_data}")
 
         if self.fcu_state.update_from_hbt(hb_data):