Fun with Interrupts

Something I avoided in college until my senior year was interrupts and interrupt service routines . 

They seemed a little scary.  Interrupts could happen at anything .  The service routines and to be fast and short .  

But they can make life easier and they're what makes multitasking possible .  

There are other ways , but I think a program that keeps checking a pin to see if a dit is still a dit , or if it's turned into a dash, or if some kind of space has happened , and if so , which one , would turn into a large state machine and a huge mess if not planned correctly.  

So , I sketched this out. Again, assuming a normal Arduino and an external audio source and the crude Schmitt trigger interface from a recent post.  

What I don't have worked out is the spacing values for what's a dit and what isn't . 

What's the best way to deal with a bad fist ?  

We shall see...