Applications of PPort
I recently used pport to automate the dome at the club's astronomical observatory. Last winter, we built a warmroom building which is 50 feet away; this allows us to do take pictures away from the cold and the bugs.
The problem is, we can't move the telescope much, because otherwise we'd just be pointing at the dome. Also, if we wanted to take a long exposure, we'd have to manually rotate the dome.
So, I took apart the switch that controlled manual rotation of the dome, and added a three connections which allowed me to close the "rotate-right" circuit with a relay from Radioshack. I ran a signal cable from the dome to the warmroom, and used pport to control the relay. So, I was able to rotate the dome remotely. Now, with a bit of software magic, the dome is kept in-sync with the telescope, so the two are always pointing to the same place.
If I were to spend more time on the project, I would implement bi-directional rotation, which would require a second relay. Also, I think I need a different kind of transistor, because right now, the dome rotates until I tell it to stop (so I have to have an initial "toggle-rotation" command to stop it, then it works as expected).
By the way, I have made .debs of pport, which can be found at http://www.justinpryzby.com/debian/.