Timing problem with millis

[david_2018]

@Delta_G

So let's think about this line. What happens if previousMillis is 100 and the currentMillis is 111. Then it changes the brightness and sets previousMillis to 111. So the next change will happen at 121 and not 120.

What is even worse, occasionally millis() increments by 2 instead of 1 (because the millis() interrupt occurs at 1.024mS intervals instead of exactly 1mS). This would eventually throw off the timing because the shorter delay would have a higher probability of hitting the increment by 2.

@Delta_G

The fix is to set previousMillis to where it should have triggered instead of where it did trigger.
prevBlueTimeMillis += 20;
or
prevBlueTimeMillis += 10;

That would have been my suggestion.