I have a Gumstix overo sandstorm that i have attached to a Tobi expansion board.
Have connected a usb cable to the  'usb-serial port' shown in the video.

I tried connecting with kermit
srinath@ubuntu:~$ kermit -l /dev/ttyUSB0
can't open device

Tried with ttyUSB1/2/3 etc. Nothing works

Haven't powered up the board yet, as mentioned in this site.

What am i missing?