[CentOS] Need to test serial port connection

[Robert]

Anne Wilson wrote:
>
> I'm not often beaten by things, but sometimes I have to fight them on and off 
> for quite a while before they are resolved.  I'm grateful for all the help I'm 
> getting here.  I shan't be giving up for a good while yet :-) if at all.
>
> Anne
RS232C is enough to kick anyone's butt.  For openers, the RS232C 
"standard" has been bent more ways than any other so-called standard 
I've ever worked with.  I would never attack a situation such as you 
have (nothing given, find everything and prove 3 ways) without a 
breakout box.  Lacking one of those, you might find the statserial 
program to be of some use in figuring out what the control lines are doing.
#  yum --enablerepo=dag install statserial
will install it.  It has a short man page.   Run with no options except 
device ( # statserial /dev/ttyS0 )  will cause it to loop, indicating 
status of all control signals.   You can manually tweak any of the pins 
with direction of "in" with a 9-volt battery or by using a paper-clip 
jumper from one of the "out" lines.  It won't be long before you can 
identify the port, moving an "unknown" to "found". 

Good luck!