topic Re: TPM timer initial delay when using 32kHz EXTAL in Kinetis Microcontrollers

TPM timer initial delay when using 32kHz EXTAL

jpatel1 — Fri, 01 Feb 2019 08:50:06 GMT

I'm trying to use TPM clock on KL17 using external 32kHz crystal. I've initialized MOD value with 32, so expecting it to interrupt after 1ms.

But I always get the first interrupt from tpm counter after 120ms delay, subsequent interrupts happen at 1ms interval.

Any pointers to debugging this issue?

Re: TPM timer initial delay when using 32kHz EXTAL

vicentegomez — Thu, 07 Feb 2019 03:14:25 GMT

How are you measuring the first pulse, remember you will need to add the time for the clock stabilization

Re: TPM timer initial delay when using 32kHz EXTAL

jpatel1 — Thu, 14 Mar 2019 22:31:57 GMT

Thanks Vincente for the response!

I am using gpio pin toggle when I initialize TPM timer and when I receive interrupt; measuring the delay using oscilloscope.

what is the best way to verify in code if crystal/clock stabilization has happened?

I am using VLPS3 sleep mode with RTC configured for external crystal. I was expecting the delay will not happen when waking up from sleep as OSC still running in sleep mode. What am I missing here?