[beagleboard] omap3530 problems with uart1

Hi
I'm using an OMAP3530 board.
I need to connect it a mifare read/write module,using pins of RX and
TX of uart1.
I think that uart1 corresponds to /dev/ttyS0, it's ok?

Making preliminary test I wanted to see if this port really transmit/
receive signal.
So, using a program like minicom and an oscilloscope, I tried to open
and transmit something on this line.
I expected to have a variation in the TX pin's voltage, but there
wasn't any variation.

Which may be the problem?

Is there something to do to "activate" the uart?

Can you help me?
Thanks.
Luca.