open UART of dm355 evm

hi,all

     on dm355 EVM. I think that I make use of UART0 to monitor and make use of UART1 to communicate with microproceesor;

but    :

        int fd = open("/dev/ttyS1",O_RDWR);

.......

run code:

         display : No such file or directory

please tell me how to open UART1?

Thank you!