First, I apologize for not responding to RobTX’s first post. I must have lost track. I don’t have enough knowledge to comment on commercial 2-wire systems. These systems are closed source so we don’t know the encoding mechanism without some serious reverse engineer efforts. I also suspect different companies use different schemes, so I don’t know how practical it is to add support for these systems.
Second, I believe it’s possible to use expansion board with a custom extension cable of a couple hundred feet long. I’ve heard some users have done this using a long Ethernet cable.
Next, we will soon add support for remote sprinkler stations installed on a different OpenSprinkler — say if you have two OpenSprinklers, you can use one as a master controller, and specify stations that physically exist on the second OpenSprinkler. This should be a fairly simple firmware change — as of now the firmware already supports remote RF stations, which allows OpenSprinkler to switch remote power sockets.
Regarding Paul’s comments: the OpenSprinkler expansion board is already a board that has shift registers and triacs. It’s basically a way to use cascaded shift registers to extend the number of stations. Is this similar to what you described?