Use RTC or app_timer?

[Pablo]

Hello, i need to count 1 or 2 minutes. Someone can recommend me if to do that is easier to use app_timer or RTC?

Which is the value that i have to put in the prescaler?

I work with nRF51 DK and soft device s130.

[Sigurd]

I suggest you use the app timer library in the SDK. The app timer uses the RTC1. Also take a look at the Application Timer Tutorial.