You said “I had considered doing API calls to OpenSprinkler, but the combo of fooling with things like the password hash for a local program and dealing with the fact that I was uncertain whether the call would trigger only the valves I wanted or also trigger the master attached to them (not wanted), I decided I wanted a little more direct interface to the valves.”
I am honestly very confused by your statements: first of all, the password is md5 hashed but it’s static. For example, if plain text password is ‘opendoor’, the md5 hash is ‘a6d82bced638de3def1e9bbb4983225c’. It won’t change unless if you change your password. So I don’t know what you mean by ‘fooling with password hash’.
Second, if you don’t want a valve to trigger the master attached to it, then you can set that valve to not activate master. This can be easily set in the web UI / mobile app for each individual station.