nmea_gps_driver in launch file

edit

Hi, I am creating a launch file for my robot, I am trying to run the nmea_gps_driver in my launchfile this is what I have so far:

<launch> 
<node pkg="nmea_gps_driver" name="nmea_gps_launch" type="nmea_gps_driver.py" args="_port:=/dev/ttyUSB0 _baud:=9600"/>
</launch>

But when I launch it I get the following message and then error:

 File "/opt/ros/groovy/stacks/nmea_gps_driver/src/nmea_gps_driver.py", line 112, in <module>
    data = GPS.readline()
  File "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 449, in read
    buf = os.read(self.fd, size-len(read))
OSError: [Errno 11] Resource temporarily unavailable

[nmea_gps_launch-27] process has died [pid 17480, exit code 1, cmd /opt/ros/groovy/stacks/nmea_gps_driver/src/nmea_gps_driver.py _port:=/dev/ttyUSB0 _baud:=9600 __name:=nmea_gps_launch __log:=/home/alex/.ros/log/60c20282-e895-11e2-8751-6036dd23d944/nmea_gps_launch-27.log].
log file: /home/alex/.ros/log/60c20282-e895-11e2-8751-6036dd23d944/nmea_gps_launch-27*.log

It is definatly a 9600 Baud Reciever and is showing up as /dev/ttyUSB0.

The following command works perfectly in the terminal and the GPS publishes data.

$ rosrun nmea_gps_driver nmea_gps_driver.py _port:=/dev/ttyUSB0 _baud:=9600

Any Ideas?