NT7S

/*
Si5351 VFO

By LA3PNA  27 March 2015
Modified by NT7S  25 April 2015

Modified to be Si5351 Arduino v2 compliant by NT7S  21 Nov 2016

This version uses the new version of the Si5351 library from NT7S.
see: http://arduino.cc/en/Reference/AttachInterrupt for what pins that have interrupts.

JChristensen

Simple demonstrations of putting AVR microcontrollers to sleep in power-down mode,
which results in minimum current.  Coded with Arduino IDE version 1.0.4 (and with
the Arduino-Tiny core for the ATtiny MCUs, http://code.google.com/p/arduino-tiny/)

For ATmega328P, ~0.1µA.
For ATtinyX5 revisions that implement software BOD disable, ~0.1µA,
for ATtinyX5 revisions that don't, ~20µA.