topic Re: Real Time Counter - rt1020 in i.MX RT Crossover MCUs

Real Time Counter - rt1020

estacey — Wed, 04 Mar 2020 15:36:59 GMT

I'm exploring the option of using the SNVS real time counter as a polled PIT. The SDK demo projects don't use the counter that way. I'm wondering how do I determine the period of the counter programmatically?

Thanks,

Ellen

Re: Real Time Counter - rt1020

jeremyzhou — Thu, 05 Mar 2020 03:33:38 GMT

Hi Ellen Stacey,

Thank you for your interest in NXP Semiconductor products and for the opportunity to serve you.
I'm not very clear with your question, whether you can want to implement the periodic Interrupt feature of the RTC, if yes, please refer to snvs_hp_rtc demo in the SDK library.

Have a great day,
TIC

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Re: Real Time Counter - rt1020

estacey — Thu, 05 Mar 2020 14:03:23 GMT

No, we're polling the count for time elapsed so I need to know the period of the count. We're doing this as a work around for our timer interrupt causing exceptions when we are erasing flash.

Re: Real Time Counter - rt1020

jeremyzhou — Fri, 06 Mar 2020 03:34:16 GMT

Hi Ellen Stacey,

Thank you for your clarification。
It means that you want to monitor the counter value to evaluate the elapsed time, and it needs to modify the rtc demo in the SDK library by yourself to implement that.

Have a great day,
TIC

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Re: Real Time Counter - rt1020

estacey — Mon, 09 Mar 2020 12:05:01 GMT

Yes, I understand that. The question is, is there a way to determine the period of the clock source in code or do I need to hard code it to a fixed value? Thank you

Re: Real Time Counter - rt1020

jeremyzhou — Tue, 10 Mar 2020 02:48:42 GMT

Hi Ellen Stacey,

Thanks for your reply.
The RTC clock source is from either Internal ring oscillator or RTC_XTAL (external crystal), in general, the internal oscillator is not precise relative to a crystal and RTC oscillators are either implemented with 32 kHz or 32.768 kHz crystals.
The RTC clock period won't change via the software code once the clock source has been selected.

Have a great day,
TIC

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