serial login to SBC

[jerry at evasefor.com]

Hello list,
I am trying to use a FreeBSD box to log into a Single Board Computer. I
have a null modem and it's plugged to both serial
ports. The SBC runs openbsd ( /dev/cua00).
When I run "cu -l /dev/cuaa0" from FreeBSD, I don't get any login
prompt. 
 
What I am doing wrong? 

I've already read the FBSD handbook.
I have an OpenBSD box to experiment with first, and can't serial login
either.
I really need help on this one.
Thank you