This short guide is about starting first project with IAR Embedded Workbench for Atmel AVR. IDE is not free, bet there is free KickStart edition with 4KB code limit.
This meter gives the best results at 0 – 1000 Hz range. It works by measuring square wave total and high period duration using 16 bit hardware counter.
As you may know frequency = 1/Period and Duty Cycle = High period duration/total period duration.