add ability to write to EEPROM

I post it here just for completenedd
I've found the reference page in the AVR-libc manuals
http://www.sigterm.de/projects/sens-o-nuts/Dokumentation/atmel/libc/group__avr__eeprom.html

I can say that your code is way more clear :slight_smile:
but hey...it's just a reference

cheers
b.