Hi Udo,
I like your approach (without dislike of the other helpful forum member!).
What I try to achieve is to get a 5V trigger signal from outside and kick a 5V signal out after a certain time. I think from my code using functions like "ignite" its clear that this will be an engine ignition. I receive a trigger from Flywheel and kick the sinusoidal 5V signal (rectangularized by a comparator) out with a certain delay. I will use the "while" command to execute a delay without using "delay()" command.
The tests I have done shown on the osicilloscope where done without any delay function but only immediate putting the PIN to HIGH only.
The only thing I need is a consistent execution of ISR...not necessarily a quick one. I need to trust this execution time is correct without jumping around 20microseconds