Sleep time logic

[ebaauw]

Currently Homebridge ZP requires a minimum Set Duration of 61s to activate the sleep timer, even though the zone player supports a sleep timer of 1s. The reasoning is that Eve enforced a minumum Set Duration (Default Duration in Eve) if 10s, so you cannot unset the timer once set.

It actually makes more sense to reset the Set Duration to 0 after switching the zone player on (cf. Transition Time in Homebridge Hue), so it can be used in HomeKit scenes, e.g. to sound the Sonos chime when the door bell is rung.