ucom — USB tty support

       Prior to FreeBSD 6.0 ucom created /dev/ucom? rather than the uniform device  names  created  today.   Old
       scripts must be adjusted accordingly.

Debian                                           April 25, 2018                                          UCOM(4)

       The  ucom  driver  attaches  to USB modems, serial ports, and other devices that need to look like a tty.
       The ucom driver shows a behavior like a tty(4).  This means that normal programs such as tip(1) or ppp(8)
       can be used to access the device.

/dev/ttyU*       for callin ports
       /dev/ttyU*.init/dev/ttyU*.lock  corresponding callin initial-state and lock-state devices

       /dev/cuaU*       for callout ports
       /dev/cuaU*.init/dev/cuaU*.lock  corresponding callout initial-state and lock-state devices

       The  ucom  driver  was adopted from NetBSD in March of 2002.  This manual page was adopted from NetBSD by
       Tom Rhodes <trhodes@FreeBSD.org> in April 2002.

       ucom — USB tty support

       The ucom driver can capture PPS timing information as  defined  in  RFC  2783.   The  API,  accessed  via
       ioctl(2),  is  available on the tty device.  To use the PPS capture feature with ntpd(8), symlink the tty
       device to /dev/pps0.

       The hw.usb.ucom.pps_mode sysctl configures the PPS capture mode.  It can  be  set  in  loader.conf(5)  or
       sysctl.conf(5).  The following capture modes are available:
           0     Capture disabled (default).
           1     Capture pulses on the CTS line.
           2     Capture pulses on the DCD line.

tty(4), uark(4), ubsa(4), ubser(4), uchcom(4), ucycom(4), ufoma(4), uftdi(4), uhso(4), uipaq(4), umcs(4),
       umct(4), umodem(4), umoscom(4), uplcom(4), usb(4), uslcom(4), uvisor(4), uvscom(4)

       To compile this driver into the kernel, place the following line in your kernel configuration file:

             deviceucom

       Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):

             ucom_load="YES"

       The following variables are available as both sysctl(8) variables and loader(8) tunables:

       hw.usb.ucom.debug
               Debug output level, where 0 is debugging  disabled  and  larger  values  increase  debug  message
               verbosity.  Default is 0.

       hw.usb.ucom.device_mode_console
               When  set  to  1, the ucom driver will mark terminals as console devices when operating in device
               mode.  Default is 1.

       hw.usb.ucom.pps_mode
               Enables and configure PPS capture mode as described below.