help testing serial port

Doug Poland doug at
Fri Apr 18 08:21:16 PDT 2003

JoeB said:
> Doug said:
> >
> >I'm trying to hook up an APC SmartUPS to a 16450 serial port on an
> >old 80486.  The box is running 4.8-STABLE and is otherwise
> >up-to-date.
> >
> >apcupsd is telling me that it cannot communicate with the UPS via
> >the serial port.  Both the cable and UPS are fine, I can commuicate
> >with the UPS with the same cable on another 80486 with a 16550A
> >serial port.  Also, the apcupsd.conf has been successfully tested
> >on another machine.
> >
> >How can I test the serial port itself to see if it's working?  I
> >tried cu -s 2400 -e -o -h -l /dev/cuaa0 and said it was connected.
> >I exited cu but now cannot attach ( cu: /dev/cuaa0: Line in use ).
> >Obviously I don't understand the fundamentals and tools necessary
> >to communicate with a serial port.  The handbook and list archives
> >haven't been much help.
> >
> >Could someone point me to a FAQ/archive/tutorial on how to debug a
> >serial port?
> >
> Check the motherboard setup bios and make sure you have the serial
> ports active.
Thanks, I'll do that.


More information about the freebsd-questions mailing list