OSPi only works for 24VAC sprinkler valves and does not work for latching valves. It would take quite a lot of work to modify it to work with latching valves.
The only controllers that we have currently that work with latching valves are OpenSprinkler Latch, and OSBee. OpenSprinkler Latch runs the full OpenSprinkler firmware and supports sensors. OSBee on the other hand, is meant for small projects that need no more than 3 zones.