Update device only when value changes?

[racarter]

Question for seasoned plug-in developers:

If you’re polling a serial device in a plug-in is it best to check in Lua if the value has changed and only update the device if it has, or update the device regardless after every poll?

Or doesn’t it matter?

[guessed]

There’s effectively a “repeat” flag on each State Variable that’ll determine whether setting the “same” value causes change-events to fire or not.

There are cases where this is important (like SecuritySensor1) so you might choose to test-then-set in those cases.

For the most part it really doesn’t matter though… unless you particularly want to be cautious on write-cycles (since these can cause the data to be marked as dirty, etc, even if events don’t fire)

Most of my stuff I just “set”, even if it already has that value. SecuritySensor1 stuff I tend to test-then-set to minimize the likelihood of dup notifications.

That said, if I were polling often I’d consider using test-then-set since, eventually, these “changes” need to be written out to [flash] disk.

[racarter]

Thanks guessed - it was indeed the flash disk writing issue I was thinking about. The plug-in to which I refer is for a security panel so frequent polling is necessary. My code tests before setting, but I’d been wondering if it was worth the effort. I’ll leave it in.