How to measure Time/count Interval on External Interrupt?

Hello ,

In this scenario, I have to measure the time interval between the START and STOP pulses generated by a peripheral device connected to nRF52 DK. The thing is START and STOP signals are passed through an OR gate to the nRF52(so, start and stop is received on a single pin). So the counter/Timer should measure between pulses START(LotoHI) and STOP(LotoHI). I tried to implement it using the pin_change_init example in which Timer0 is initialized and called from the interrupt handler function. But I could not make it work.

Appreciate if someone tech savvy could help me out in this matter. 

FYI Time interval range is 1.34microseconds - 38 microseconds and ref image for start and stop is attached.

Thanks

Cheers!

Updated 2019/05/17

I could get the START and STOP events working, now i am unable to capture the time interval between START and STOP pulses. Please share insights.

Program code that I tried to implement the time capture between START and STOP tasks. 

Edited 2019/05/19

Removed Code from the post.

I was able to get the exact thing implemented using PPI,GPIOTE and TIMER. 

This following link is useful if anybody gets to this post

https://devzone.nordicsemi.com/f/nordic-q-a/23267/how-to-measure-two-wave-delay/91489#91489