Port already used problem with autodetect

now i have some problems with the first start of poppy.
whatever the code i input, i get the dxlerror: Port already /dev/used ttyUSB1
for example this code:

from pypot.dynamixel import autodetect_robot
my_robot = autodetect_robot()

for m in my_robot.motors:
m.goal_position = 0.0

then i get the error:

DxlError Traceback (most recent call last)
in ()
1 from pypot.dynamixel import autodetect_robot
2
----> 3 my_robot = autodetect_robot()
4
5 for m in my_robot.motors:

/usr/local/lib/python2.7/dist-packages/pypot-2.5.0-py2.7.egg/pypot/dynamixel/init.pyc in autodetect_robot()
67 for port in get_available_ports():
68 for DxlIOCls in (DxlIO, Dxl320IO):
—> 69 dxl_io = DxlIOCls(port)
70 ids = dxl_io.scan()
71

/usr/local/lib/python2.7/dist-packages/pypot-2.5.0-py2.7.egg/pypot/dynamixel/io/abstract_io.pyc in init(self, port, baudrate, timeout, use_sync_read, error_handler_cls, convert)
70 self._serial_lock = threading.Lock()
71
—> 72 self.open(port, baudrate, timeout)
73
74 def enter(self):

/usr/local/lib/python2.7/dist-packages/pypot-2.5.0-py2.7.egg/pypot/dynamixel/io/abstract_io.pyc in open(self, port, baudrate, timeout)
93
94 “”"
—> 95 self._open(port, baudrate, timeout)
96 logger.info(“Opening port ‘%s’”, self.port,
97 extra={‘port’: port,

/usr/local/lib/python2.7/dist-packages/pypot-2.5.0-py2.7.egg/pypot/dynamixel/io/abstract_io.pyc in _open(self, port, baudrate, timeout, max_recursion)
115
116 if port in self.__used_ports:
→ 117 raise DxlError(‘port already used {}’.format(port))
118
119 # Dirty walkaround to fix a strange bug.

DxlError: port already used /dev/ttyUSB4

has anyone know the reason and what could be my problem?

this is exactly the same problem as here:

this is the same problem. but i still don’t know what could be the problem?
In addition i will get this error for some other example with port.
for example:

import pypot.dynamixel

ports = pypot.dynamixel.get_available_ports()

if not ports:
raise IOError(‘no port found!’)

print(‘ports found’, ports)

print(‘connecting on the first available port:’, ports[0])
dxl_io = pypot.dynamixel.DxlIO(ports[0])