Posted on May 17, 2011 at 14:30You could measure the 1 Hz RTC tick against ticks of the HSI or HSE clocks over the 1 second observation period.
They both have better accuracy than the ~40 KHz 8% LSI, not that the LSI has any voltage or temperature stability to be worth calibrating. Unless you have some way to sync against an external source (GPS, NTP, 1588) periodically, you will have trouble maintaining an accurate time.
Using a more accurate LSE source would be a more productive choice.
