adding verification of packets and logic to handle all types of packets

pydecentscale/__init__.py

@@ -11,6 +11,12 @@
 from threading import Thread
 from itertools import cycle
 from bleak import BleakScanner,BleakClient
+import logging
+import functools
+import operator
+
+
+logger = logging.getLogger(__name__)
 
 
 class AsyncioEventLoopThread(threading.Thread):
@@ -155,9 +161,40 @@ async def _reset_time(self):
             await asyncio.sleep(0.2)
             await self.client.write_gatt_char(self.CHAR_WRITE,self.reset_time_command)
 
+    def notification_handler(self, sender, data):
+        if data[0] != 0x03 or len(data) != 7:
+            # Basic sanity check
+            logger.info("Invalid notification: not a Decent Scale?")
+            return
+
+        # Calculate XOR
+        xor_msg = functools.reduce(operator.xor, data[:-1])
+        if xor_msg != data[-1]:
+            logger.warning("XOR verification failed for notification")
+            return
 
-    def notification_handler(self,sender, data):
-        self.weight=int.from_bytes(data[2:4], byteorder='big', signed=True)/10
+        # Have to decide by type of the package
+        type_ = data[1]
+
+        if type_ in [0xCA, 0xCE]:
+            # Weight information
+            self.weight = int.from_bytes(data[2:4], byteorder='big', signed=True) / 10
+        elif type_ == 0xAA:
+            # Button press
+            # NOTE: Despite the API documentation saying the XOR field is 0x00, it actually contains the XOR
+            logger.debug(f"Button press: {data[2]}, duration: {data[3]}")
+        elif type_ == 0x0F:
+            # tare increment
+            pass
+        elif type_ == 0x0A:
+            # LED on/off -> returns units and battery level
+            logger.debug(f"Unit of scale: {'g' if data[3] == 0 else 'oz'}, battery level: {data[4]}%")
+        elif type_ == 0x0B:
+            # Timer
+            # NOTE: The API documentation says there is a section on "Receiving Timer Info" but this is missing
+            pass
+        else:
+            logger.warning(f"Unknown Notification Type received: 0x{type_:02x}")
 
     async def _enable_notification(self):
         await self.client.start_notify(self.CHAR_READ, self.notification_handler)
@@ -201,7 +238,8 @@ def disconnect(self):
         return self.connected
 
     def auto_connect(self,n_retries=3):    
-
+        address = None
+
         for i in range(n_retries):
             address=self.find_address()
             if address: