ros_arduino_bridge configuration error

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Hi, i follow read me tutorial of ros_arduino_bridge in this link link text and when i run roslaunch ros_arduino_python arduino.launch, i receive this error:

Connecting to Arduino on port /dev/ttyACM0 ... Traceback (most recent call last): File "/home/irisecesi/catkin_ws/src/ros_arduino_bridge/ros_arduino_python/nodes/arduino_node.py", line 195, in <module> myArduino = ArduinoROS() File "/home/irisecesi/catkin_ws/src/ros_arduino_bridge/ros_arduino_python/nodes/arduino_node.py", line 87, in __init__ self.controller.connect() File "/home/irisecesi/catkin_ws/src/ros_arduino_bridge/ros_arduino_python/src/ros_arduino_python/arduino_driver.py", line 68, in connect test = self.get_baud() File "/home/irisecesi/catkin_ws/src/ros_arduino_bridge/ros_arduino_python/src/ros_arduino_python/arduino_driver.py", line 261, in get_baud return int(self.execute('b')); File "/home/irisecesi/catkin_ws/src/ros_arduino_bridge/ros_arduino_python/src/ros_arduino_python/arduino_driver.py", line 178, in execute return int(value) TypeError: int() argument must be a string or a number, not 'NoneType' [INFO] [WallTime: 1468423834.069478] Stopping the robot... [INFO] [WallTime: 1468423834.070452] Shutting down Arduino Node... [arduino-1] process has died [pid 10979, exit code 1, cmd /home/irisecesi/catkin_ws/src/ros_arduino_bridge/ros_arduino_python/nodes/arduino_node.py __name:=arduino __log:=/home/irisecesi/.ros/log/3ed0dd4c-4904-11e6-9d6d-eca86bf97b81/arduino-1.log]. log file: /home/irisecesi/.ros/log/3ed0dd4c-4904-11e6-9d6d-eca86bf97b81/arduino-1*.log all processes on machine have died, roslaunch will exit shutting down processing monitor... ... shutting down processing monitor complete done

What can i do please?