Kinetis Microcontrollers中的主题 Re: K24 RTC compenstation

K24 RTC compenstation

yuanli — Fri, 27 Mar 2015 03:05:15 GMT

Hi,

Is there any doc to guidance how to compensate K24 RTC?

Customer is using external RTC clock, When run the MCU continuously for 5 days, there are 23 seconds difference between MCU and PC.

Please help advise how to compensate it, thanks.

Best regards,

Ryan

Re: K24 RTC compenstation

santiago_gonzal — Fri, 27 Mar 2015 11:21:07 GMT

Hello Yuan Li,

Have a look here:

http://cache.freescale.com/files/microcontrollers/doc/app_note/AN4949.pdf

Regards,

Santiago

Re: K24 RTC compenstation

egoodii — Mon, 30 Mar 2015 13:30:26 GMT

You should be able to do 'a lot better' than 4s/day just by setting the proper chip load-capacitors. See my discussion:

Re: RTC accuracy with MQX 4.1 on a K70

But as I say there, your 'worst case parts' will still only get you about 2s/day at room temperature with 'inexpensive' crystals -- a nice oscillator can hold 1s/day. The APNOTE mentioned above helps you improve a crystal over temperature, BUT that requires the CPU to be 'awake', at least periodically, to be able to MEASURE said temperature and 'do something with it' -- the SiTime part 'does that for you'.

Re: K24 RTC compenstation

yuanli — Tue, 31 Mar 2015 07:16:22 GMT

Thanks a lot for the advices from both of you, I will study and have a try. :smileyhappy: