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Using Picaxe 20x2 SPI to set ADF4106

Question asked by Vk3gjm on Nov 6, 2012
Latest reply on Jan 31, 2014 by rbrennan



I have a need to build a 3910 MHz PLL. I decided to use a Mini circuit integrated PLL/VCO part number KSN-3940. It's a great device and the base PLL uses the ADF4106.


As I need to set the frequency only once at power up and not having much experience on programming Micros, the PICAXE 20x2 when configured using hspisetup made sense and it keeps the design simple from my point of view.


Unfortunately, I am struggling to obtain a frequency anywhere near 3910 MHz using basic register values and a 20MHz ref in and a 10MHz PD


F = 0x5F8092

R = 8

N = 1819


During power cycles, I can obtain a mix out digital lock for ~2940MHz, however it's all over the place and obviously a false lock.


I have reviewed the Latch, clock and data alignment on a digital CRO, they appear to be fine and closely match the data sheet timing diagram.


After 2 days of experimenting, I am at a total loss and struggle to find any answer.


The code I am working on goes like this


#picaxe 20m2


hspisetup spimode00,spislow


symbol LE = c.0



high LE

pause 100



'====  F-Register =========

low LE  

hspiout  (%01011111,%10000000,%10010010)  '24bits

high LE


'===== N-Register ========

low LE

hspiout  (%00000000,%00011000,%00101001)  '24 bits

high LE


'====== R-Register ========

Low LE

hspiout  (%00000000,%00000000,%00001000)  '24bits

high LE


Standard pins used on the 20x2 are


Pin 9 SPI data out

Pin 10 LE

Pin 11 SPI CLK


I know this isn't an answer AD could possibly give, I hope another user may have greater experience with ADF4106 and Picaxe.