I recently purchased an original Poqet PC, along with a serial link cable.
I carefully studied:

General Information about the Poqet PC, the best on the web:
http://www.bmason.com/PoqetPC/

Specifically about Making the upload/download Serial Connections
http://www.njqrp.org/poqetpc/wj2v%20review.html

Details about the Poqet PC Expansion Bus, including pin outs.
http://www.bmason.com/PoqetPC/docs/p.../chapter6.html

I also read several tiny articles on how to make your own serial cable
from scratch:

http://groups.google.com/groups?hl=e...b80ce1a&rnum=1