- redefine activate method

- for task introduced open() conext method

tasks/stirrer.py

@@ -21,9 +21,6 @@ class StirrerTask(ATask):
 	def on_cycletime_changed(self, value):
 		asyncio.create_task(self.send({'CycleTime': value}))
 
-	def on_changed_active(self, is_activated):
-		asyncio.create_task(self.send({'Activate': int(is_activated)}))
-
 	async def recv(self, data):
 		for pair in data.items():
 			if 'Speed' in pair[0]:
@@ -39,12 +36,12 @@ class StirrerTask(ATask):
 		self.device.set_on_changed("speed", self.on_speed_changed)
 		self.device.set_on_changed("dutyCycle", self.on_dutycycle_changed)
 		self.device.set_on_changed("cycleTime", self.on_cycletime_changed)
-		self.device.set_on_changed('is_active', ChangedInteger(self.on_changed_active).set)
 
 		self.device.set_speed(50.0)
 		self.device.set_cycle_time(10.0)
 		self.device.set_duty_cycle(1.0)
 
-		while True:
-			self.device.process()
-			await asyncio.sleep(self.interval)
+		with self.device.open():
+			while True:
+				self.device.process()
+				await asyncio.sleep(self.interval)