For enable use external (LSE) clock generator need un comment in Makefile
#UDEFS+= -DVNA_USE_LSE
By default use internal (LSI) clock generator, but it stop then VNA power off
For enable use external (LSE) clock generator, need install 32.768kHz clock quartz on PC14 and PC15 pins, it allow clock run while power off
For enable use RTC in code uncomment in nanovna.h
#define __USE_RTC__
This enable command 'time'
usage: time [y|m|d|h|min|sec] 0-99
Example set 2020 year run 'time y 20'
Add show current time in version screen
Better use font size constants for all screen size
