help testing serial port

JoeB barbish at
Fri Apr 18 07:56:32 PDT 2003

Check the motherboard setup bios and make sure you have the serial
ports active.

-----Original Message-----
From: owner-freebsd-questions at
[mailto:owner-freebsd-questions at]On Behalf Of Doug Poland
Sent: Friday, April 18, 2003 10:33 AM
To: questions at
Subject: help testing serial port


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

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
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?


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