ax2550 node fails to connect to ax2550?

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Hello, I'm using a ROS driver for the ax2550 motor controller found here:

https://github.com/wjwwood/ax2550

(I couldn't figure out the actual download, so I just created my own project and copied the text into each file, then catkin_made. I don't think this is the source of my problems, since it compiled, and worked for a similar device driver that I got working just yesterday.)

I have plugged the device into a serial-->usb converter, which then goes into my computer. However, when I run the node using:

rosrun ax2550 ax2550_node /dev/ttyUSB0 (this is the port its connected to)

I get the following response:

[ INFO] [1405371811.620859117]: AX2550 connecting to port /dev/ttyUSB0
[ERROR] [1405371811.621207096]: Failed to connect to the AX2550: IO Exception (13): Permission denied, file /tmp/buildd/ros-hydro-serial-1.1.7-0precise-20140617-0339/src/impl/unix.cc, line 150.
[ INFO] [1405371811.621317396]: Will try to reconnect to the AX2550 in 5 seconds.

It looks like this is a permissions error (despite the fact that I am the administrator), but I don't know for sure and if it is I don't know how to change these permissions. Anyone got any ideas?

Thanks

New info:

I ran the line sudo chmod 777 /dev/ttyUSB0, which solved the error I was initially having. However, I am now encountering a new error when I try to run the node: [ INFO] [1405453884.235150040]: AX2550 connecting to port /dev/ttyUSB0 [ERROR] [1405453886.236099864]: Failed to connect to the AX2550: Synchronization Exception: did not receive an R/C message after reset, file /home/randy/catkin_ws/src/toro/src/ax2550.cpp, line 315. [ INFO] [1405453886.503068921]: Will try to reconnect to the AX2550 in 5 seconds. Any idea what could be causing this one?