Instructions 

It is really easy to connect the arduino (with an usb connection) to the wl500g.

You need the following packages from openwrt: kmod-usb-serial, kmod-usb-serial-ftdi

Upload the Sketchbook -> Examples -> Communication -> PhysicalPixel onto the arduino on your normal computer.

Connect the arduino to the wl500g and load the modules (usbserial, ftdi_sio)

 It will create a serial port at /dev/usb/tts/0 (could be a different number, use dmesg to see the log)

Turn off the led: 

$ echo L > /dev/usb/tts/0    

 Turn on the led:

$ echo H > /dev/usb/tts/0

or use screen 

$ screen /dev/usb/tts/0 9600

More information:

• arduino 
• openwrt arduino hotplug script
• arduino and the linux tty  
• blinking koffer openwrt , add 220v and turn your lights on and off from the internet