增加连接下位机，断开下位机时候的蜂鸣器声音提示

src/ros_arduino_bridge/ros_arduino_python/src/ros_arduino_python/arduino_driver.py

@@ -69,8 +69,8 @@ class Arduino:
                 test = self.get_baud()
                 if test != self.baudrate:
                     raise SerialException
-            
-            beep_ring(1)
+
+            self.beep_ring(1)
             print "Connected at", self.baudrate
             print "Arduino is ready."
         except SerialException:
@@ -89,7 +89,7 @@ class Arduino:
     def close(self):
         ''' Close the serial port.
         '''
-        beep_ring(0)
+        self.beep_ring(0)
         self.port.close()
 
     def send(self, cmd):