Hi Farhan, Have started reading through the Audrino source to try and understand the project. Got some questions:- 1. Wondering where the name "radiono" originates from, why not minima.ino? Is radiono the concatenation of radio !! (Audri) no? Is this to keep the software project controlling the digital VFO separate from "Minima" which will soon have an Analog VFO+control option? 2. The comment on Line 140:- 140: //we have to read eight consecutive registers starting at register 5 perhaps this should actually be:- 140: //we have to read six consecutive registers starting at register 7 ??? At least that what I think the code seems to do. Already mentioned this in direct e-mail but I don't believe the 3hz step in lines 386 and 413 can ever be executed. I've been reading the Silicon Labs App Note An334 and the Si570 Datasheet. Man trying to get your head round programming one of these critters is enough drive a grown man to algebra! Just as well kind souls have already done the hard work on the low level routines!!! :-) I think this may come in handy after I understand a little more:- http://www.zs6buj.com/files/General/ZS6BUJ_Si570_Calculator.xls‎ 73, Steve VK2SJA