Problem with parameter in launch file [closed]

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Hello,

I am working with a Raspberry Pi and an Arduino on ROS indigo. I wrote this script to launch multiple nodes.

<launch>
    <node pkg="beginner_tutorials" name="xbox_joy" type="xbox_joy.py"/>
    <node pkg="joy" name="joy_node" type="joy_node"/>
        <param name="joy_node/dev" value="/dev/input/js1" />
    <node pkg="rosserial_python" name="serial_node" type="serial_node.py"/>
        <param name="port" value="/dev/ttyACM0"/>
        <param name="baud" value="115200"/>
</launch>

All nodes and parameters work, except the last one : port parameter from serial_node is not taken into account. So I get the message :

process[rosout-1]: started with pid [4606]
started core service [/rosout]
process[xbox_joy-2]: started with pid [4610]
process[joy_node-3]: started with pid [4624]
process[serial_node-4]: started with pid [4625]
  pub = rospy.Publisher('/cmd_vel',Twist)
[ERROR] [WallTime: 1492157910.346003] Error opening serial: could not open port /dev/ttyUSB0: [Errno 2] No such file or directory: '/dev/ttyUSB0'
[serial_node-4] process has finished cleanly

Roscore is looking for port /dev/ttyUSB0, instead the given one : /dev/ttyACM0. Anybody know what I am doing wrong ?

Regards

Matthieu