I have an STM32F411RE nucleoboard. I tried to test my delay fnc with input cpature mode. It seems the prescaler not divide the frequency only after overflow of the capture compare register.

[MSzal.1]

Hi everybody!

First of all sorry for my language. I just started to learning programming of STM32. My problem is that i made a delay function. I wanted to test it with the input capture mode. I setted the prescaler to 16000 - 1. I wanted to get an 1000 Hz sampling. When I start to debug the project as you can see in the microsecs_wrong.png file, the difference between the timestamps is 32.000.000. The interesting part is when the capture compare register reaches 4294967295 (2^32 - 1) it overflows and start to works properly (microsecs_proper_working.png). The difference between timestamps now is 2000. Why is that happening?

Thanks for Your help!! :)

[TDK · Accepted solution]

The PSC and ARR registers are preloaded by default. If you want them to take effect immediately, generate an update event after setting it but before enabling the timer.

TIM2->EGR = TIM_EGR_UG;

[MSzal.1]

It works fine! Thank you!! :)