<!DOCTYPE txt>
<!Version: 0.1>
<!Date: 16.11.2017>


raspi-config

---------------------------
Interfacing Options

I2C enable
----------------------------

nano /boot/config.txt

add at end
--------------------------
# Enable HWclock
dtoverlay=i2c-rtc,ds3231
-------------------------

nano /lib/udev/hwclock-set

comment out
--------------------------

if [ -e /run/systemd/system ] ; then
exit 0
fi
-------------------------


Good to know:

read time directly from rtc module
hwclock -r

update rtc module time from system time (system time should be regularly updated by ntp from the internet if your pi is networked):
hwclock -w

update system time from the rtc module (this should happen on startup):
hwclock -s

and the most fun of all - monitor the "drift" between your system clock and the rtc module:
hwclock -c
