Unable to open serial port error in SICKToolBOX wrapper?

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Hi,

I am relatively new to ROS. So apology if this question might sound trivial, but I really need help. I am following the tutorial http://wiki.ros.org/sicktoolbox_wrapp... . However, as I am trying to do rosrun sicktoolbox_wrapper sicklms, I am getting the following error:

Attempting to initialize the Sick LMS...
Attempting to open device @ /dev/ttyUSB0
ERROR: I/O exception - SickLMS2xx::_setupConnection: - Unable to open serial port
ERROR: I/O exception - SickLMS2xx::_setupConnection: - Unable to open serial port
[ERROR] [1462855550.192922717]: Initialize failed! are you using the correct device path?

Could anyone help me troubleshoot what am I doing wrong? I am using LMS291 withRS422 interface and a USB to serial adapter, and doing the following in my command line:

1. rosdep install sicktoolbox_wrapper rviz
2. rosmake sicktoolbox_wrapper rviz
3. ls -l /dev/ttyUSB0
4. roscore (in a new terminal)
5. rosparam set sicklms/port /dev/ttyUSB0
6. rosparam set sicklms/baud 38400
7. rosrun sicktoolbox_wrapper sicklms

Thanks, Shantnu Kakkar