how to count time

[David.Cheng]

I want to measure the time from GPIO low level to high in RC circuit,

how to count the time

use rtc or tim?

[Tesla DeLorean]

A free running, maximal count, TIM could be use in Input Capture mode. For high precision, long duration, use a 32-bit TIM if available.

SysTick could count off milliseconds. EXTI to interrupt on edges.

[David.Cheng]

got it, if the pin to the low value of high level, then timer should stop, Input Capture mode is ok?

[David.Cheng]

got it, capture is a precise way. if the pin P1.2 just reaches 0.70 x VDD, then timer should stop, Input Capture mode is ok?