AnsweredAssumed Answered

Input filter too short!

Question asked by Corentin Zill on Sep 22, 2017
Latest reply on Sep 25, 2017 by Corentin Zill

Hi everybody! 

I'm using the input capture digital filter function of TIM15 on STM32F070CB. I need to filter out pulses shorter than 1.5ms and I want to keep FCLK at 48MHz.

Problem is, in this case, I can't have a TIM15 timer clock slower than 6MHz (div/16*2), then divided by 4 (max.) with CKD=10, then using fDTS/32 with 8 samples (max.). This gives a period of 170us, which is definitely too short for me.

I tried to use TIM3 as prescaler for TIM15, but it doesn’t seem to work because fDTS is directly taken from fCK_INT (see AN4776), which cannot come from TIM3 (only CK_PSC of TIM15 can come from TIM3).

Any idea of configuration allowing filtering out pulses shorter than 1.5ms while keeping FCLK=48MHz?

Many thanks!!!