Tegra X1 - unable to make ttyUSB0

Hi, I am newbie about tegra and I want to study TX1 and TK1.

I want TX1 to connect usb via ttyUSB. In TK1, it automatically connects usb through ttyUSB0. However, in TX1, it does not get the ttyUSB0. Also dev/ttyUSB directory does not exists when connected!! when I type ‘lsusb’ command, it shows like 'BUS 001 Device 007: ID 046d:c01f Logitech, Inc.

what is difference between TX1 and TK1 on this issue?? and how can I connect USB through ttyUSB in TX1??

I want to use ttyUSB.