>Has anyone tried writing a NetBSD driver for an A/D I/O board?

Yes. I had a student do one a couple of years ago.  Worked quite
well.


-- 
Phil Nelson                       NetBSD: http://www.netbsd.org
e-mail: phil@cs.wwu.edu           Coda: http://www.coda.cs.cmu.edu
http://cs.wwu.edu/faculty/nelson