Thank’s for the UPS suggestion — though there’s no link, though I can find something that seems to match on Amazon.ca. I don’t know if it will fit, though it might. Having to hack into the OpenSprinkler case and find the 5vdc pads is annoying though. How do I know that a slight voltage difference won’t cause problems between the UPS and the built-in power supply? Is there already a protection circuit? There are too many unknowns to make me comfortable with this.
As for change freezes during production, well, yes, that’s what I will do, basically. The “pause” feature will work for some maintenance needs, provided the total runtime isn’t approaching 24 hours due to % watering budget compensation for the hot season. The ability to cancel zones without changing the schedule of following zones will also be used for maintenance and working in areas without getting soaked.
However having to wait 24 hours or more for a new zone to work, for example, is also rather annoying to say the least.
I.e. the same feature needed to recover after a reboot could also be used to rebuild the schedule after a program change, i.e. without having to wait until the next day or whenever the program restarts. I should be able to add a new zone to a program, or change the ordering (by changing the zone names), and have the schedule immediately reflect those changes.
Fail safe recovery into operating mode is still required for crashes too — unless you can somehow give me a mythical guarantee that the firmware will never ever crash!