RTC Drift & Reset

[paultech]

Hello,

Measuring the RTC over long term with stable clean power shows a 30-35 ppm drift rate. (Side effect of the combination crystal?)
REG_RTC_FREQCORR is completely undocumented, see #255
Worst of all: RTC is reset apon insertion or removal of a sd card!

[dlabun]

Low level registers like REG_RTC_FREQCORR are documented by Atmel in the SAMD21 family datasheet, not in Arduino documentation. You're only going to find the high level Arduino features documented on the Arduino sites.