I found the problem:
• Insert the 24V AC wires into the orange terminal (AC has no polarity so the two wires have no distinction)
from
http://rayshobby.net/docs/os_fw214_manual.pdf
As I swapped the wires, the Opensprinkler started (without USB) immediately 🙂
But it started a valve (24 VAC only for testing purposes connected) too and never set them to “active low”.
Starting “Run-once-Program” starts the solenoid/valve immediately but never stop it. Same with “Stop All Stations”.
Disconnecting COM, station or switch off Opensprinkler stops/close the valve.
What I need to do to open and close (high-/low) the solenoids/valves ?