by mstempin Tue Nov 17, 2015 3:07 pm
Hi Ramon,
The RTC is running at 32768 kHz on the internal Low-Frequency RC Oscillator (LFRCO), not on the "external" (well, inside the module!) Low-Frequency 32 kHz Crystal Oscillator (LFXO).
It is possible to calibrate the internal RC oscillator using the external crystal with the TD_RTC_CalibratedDelay() function or lower-level CMU_Calibrate() function.
According to EFM32G210 datasheet section 3.9.3, the LFRCO accuracy is +/-4.5% and tuning steps are 1.5% typical. That is, you may be off by approximately 1 h / day.
The sync period with downlink messages depends on your required accuracy.