error servomotor

edit

hi, i need your help when i run my robot (base raspberry and arduino), it works just a small periode and i receive error in my in my node rosserial python:

[WARN] [WALLTime: 1460141186.940438] Serial Port read returned short (expected 1bytes, received instead).
[WARN] [WALLTime: 1460141186.950177] Serial Port read failure:
Traceback (most recent call last):
File "/home/pi/catkin_ws/src/rosserial/rosserial_python/nodes/serial_node.py",
line 82, in <module>
client.run()
File "/home/pi/catkin_ws/src/rosserial/rosserial_python/src/rosserial_python/SerialClient.py", line 492, in run
self.requestTopics()
File "/home/pi/catkin_ws/src/rosserial/rosserial_python/src/rosserial_python/SerialClient.py", line 389, in requestTopics()
self.port.flushInput()
File "/usr/lib/python2.7/dist-packages/serialposix.py", line 500, in flushInput

This error produice specially when i connect servomotor.