Serial port configure on beagleboard

hi guys,

i've some problem about the use of serial port on beagleboard. i've
installed ubuntu following instruction of wiki and i've red that uart1
and uart2 should be configured by default. i've try to setting up a
serial comunication but any kind of signals are present on serial port
tx pin.

i've also checked uboot configuration and it seems to be correctly
configurated.

help me!
thanks