Hi Alfredo, this is iw2fvo .
Years ago I got in touch with Nick WA5BDU to have some indication about the si570 control and thank to his suggestion I developed a sketch capable of controlling the SI570 in its whole frequency band ( up to 1.4 GHZ )
I did use this sketch on Arduino Nano as a VFO for my two meters FM receiver and for the APT receiver.
The sketch does not requires to enter pre_computed values : it performs the calculation for each one of the required frequencies.I hope this sketch will help since I was able to generate frequencies of about 300 MHz due to the limited frequency range of my si570 chip.
I will try to attach the sketch here !
Thanks Nick !
I am sorry for my bad English !!!
73, IW2FVO, Ambrogio