I looked everywhere on the net to find something that I could afford with which to connect my USB serial port to a Sun machine. I couldn't install Fink or MacPorts, and screen was garbling all of the text for the Solaris install. Finally, I started looking in general UNIX support, which led me to the cu utility.
Use the cu command to get a (more-or-less) clear line. It's part of OSX's BSD heritage, and was originally used to allow UUCP batches to dial modems and link with each other. Here's how to use set up a connection:
sudo cu -s [bitrate] --nostop -l /dev/cu.[serialdevice]This could also be used with /dev/tty.[serialdevice], I believe, though I have not tried it.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20100122181700528