measuring interrupt interval with app_timer

[paul_tanner]

I have an interrupt coming in every 50-150 microsecs and I want to measure these intervals as precisely as possible.

I tried this with SDK12.2:

APP_TIMER_INIT(0, 5, false);

then in the (GPIOTE) ISR:

uint32_t this_time=app_timer_cnt_get();

I always get zero back;

Presumably I need to initialise it in a different way?

Thx for any suggestion.

[AmbystomaLabs]

See above. I can only answer once so I added the code to my previous answer.

[paul_tanner]

Thx for that. I need to study PPI to fully understand this. I think the main point about both answers is that no extra interrupts are introduced. The timer is just available to be read in the pin interrupt's ISR. You example clears the timer which is nicer than handling overflow.