Sonoff basic toggle with low pass filtering

[pcsaito]

This PR implements a low pass filter on gpio value instead of a time debounce to toggle.

With the default parameters it will filter up to 6 wrong readings and introduces about 60ms delay.

Fixes #70

[maximkulkin]

Can the same thing be done without using tasks (e.g. interrupt handlers + timers) ? Having a task for each toggle is too expensive.

[pcsaito]

I think it is.

The only purpose I used a task is to keep a contant update on the LPF values. Anything that executes periodically could do that.

All the toggles could share the same task or interrupt handler if they share the same “refresh” rate.

Is it still preferable to use interrupts instead only one task shared with all toggles?

[pcsaito]

I implemented the only-one-task solution.

As the LPF_INTERVAL is a #define, all the toggles already have the same interval, so more than one task never made sense.

If you judge that a interrupt handlers + timers implementation is more adequate I can follow this approach, just used a task because I'm more used to it.

[maximkulkin]

Ok, since I do not have bandwidth to do it myself and since it is for this particular example only, I'm fine with current implementation as long as it improves people experiences. Maybe someday somebody will hit this problem and volunteer to improve resource usage (or maybe not).