1ms Elapsed Timer Demo with DT's Instant Interrupts

[Art]

1.. Yes.
There is a little more in the main program to handle the ext interrupt, but essentially yes (for question 2).

The main program turns external int off and clears it’s trigger flag as well at initialise time.
Then when the sync wants to happen for whatever reason (like the GPS has been locked for a minute),
the main program turns ext int on. Then I figure the next time the ISR is called by ext interrupt,
the timer should be loaded rather than added to... but added to every other time, because
the ISR turns ext int off just a little after this.

ps.. So far the time is still correct, but I can’t test lag or error of the sync to the pulse.