[beagleboard] omap3530 problems with uart1

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?