HELP: NE555 and interrupt function

Projects General Guidance
2

You have a few problems:

You are using "pin 2" for reading but your schematic shows your input hooked up to analog pin 2. That is not the same as "D2", or digital pin 2. Move your input from A2 to D2.

Second, nowhere in your code do you write to the oldTime variable. You must say something like:

oldTime = newTime;
newTime = micros();

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The Rugged Audio Shield: Line In, Mic In, Headphone Out, microSD socket, potentiometer, play/record WAV files

The Rugged Audio Shield: Line In, Mic In, Headphone Out, microSD socket, potentiometer, play/record WAV files