ubx packetizer: permit sync bytes length > 2

receiver/ubx_packetizer.py

@@ -25,7 +25,7 @@ class UbxPacketizer(MsgSink, MsgSource):
 		for n in range (0, len(msg.data)):
 			d = msg.data[n]
 			if d == self.sync_bytes[self.sync_count]:
-				self.d_save = struct.pack('B', d)
+				self.d_save += struct.pack('B', d)
 				self.sync_count += 1
 				if self.sync_count == len(self.sync_bytes):
 					print(f"{msg.name}:UBX-sync")
@@ -37,9 +37,10 @@ class UbxPacketizer(MsgSink, MsgSource):
 					self.wait_sync = False
 					self.timestamp = msg.timestamp
 			else:
-				self.sync_count = 0
+				if self.sync_count > 0:
 					self.packet += self.d_save
 					self.d_save = b''
+					self.sync_count = 0
 				if not self.wait_sync:
 					self.packet += struct.pack('B', d)
 					data, hdr = frame_parse(self.packet)