Button implementation within a long delay loop

[LarryD]

@JCA34F

timer += interval; // restart timer

Versus

@xfpd

timer = millis(); // reset timer

Versus

while ( millis() - timer > interval )
{
  timer = timer + interval;
}  

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This is an interesting discussion:

Blink Without Delay problem. Warning.

Warning to new people. I just wanted to point out a potential (major) problem with the BWD (Blink Without Delay) technique. There are two (four, see post #4) ways that the BWD timing variable can updated: Method one updates the timing variable by adding the delay time to the timing variable itself. There is an argument that this will prevent slippage in timing. millisOne = millisOne + delayTime; Method two updates the timing variable by setting it equal to the current value of millis()…