STM32F427 RTC Problem

[rozh_yinxianjun]

Posted on March 30, 2016 at 12:59

hi,

My RTC is driverd by external 32.768K  clock source. It works well，if the MCU does not enter standby mode. Let the MCU enter standby mode and wake up every 60 seconds by alarm, RTC will slow about 6 seconds during 10 minutes  .However Let the MCU enter standby mode and wake up every 300 seconds(or more) by alarm, RTC works well. Will the wake freqency have influence on RTC?

[pkumar1883]

Posted on March 30, 2016 at 13:21

Dear xianjun.yin

Run a testing cycle of 30 minute on 300 seconds wakeup and observe it there is any delay in RTC in this 30 minute cycle.

[rozh_yinxianjun]

Posted on March 30, 2016 at 15:22Dear kk:I have obseverved about 2 hours with 300 seconds wakeup.There is no obvious delay.

[rozh_yinxianjun]

Posted on March 30, 2016 at 15:46Dear kk:I have a mistake.There is about 5 seconds delay with testing cycle of 2 hour on 300 seconds。

[Walid FTITI_O]

Posted on March 30, 2016 at 16:19

Hi xianjun.yin,

Is the RTC clock source an LSE (crystal resonator) ? -Hannibal-

[rozh_yinxianjun]

Posted on March 30, 2016 at 16:31

hi Hannibal :

The RTC CLOCK is LSE(5PPM)，if the MCU do not enter standby mode ,the precision of RTC is very good. 

[Tesla DeLorean]

Posted on March 30, 2016 at 17:01

Maybe you need to review how you are advancing the time line for the alarm.

[Walid FTITI_O]

Posted on March 30, 2016 at 17:23

Hi xianjun.yin,

Check if the crystal is compatible with the device you are using by refering to

http://www.st.com/web/en/resource/technical/document/application_note/CD00221665.pdf

. (Table 7) -Hannibal-