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Programming AD9851 and/or AD9834 with PICAXE

Question asked by WB0POH on Oct 20, 2012
Latest reply on Nov 9, 2012 by zuzu

I am working on an interface that will mate up with either an AD9851 or AD9834.   The AD9834 is an SPI-compatible interface but the AD9851 is something else.  The interface is intended for a 0-60MHz VFO (for the 9851) or 0-30MHz VFO (for the 9834) for use in a low-power ham radio transmitter.  The chip I am using for the interface is a PICAXE 28x1, but I am also looking to use PICAXE 28x2 eventually.


The issue I am running into is that the PICAXE SPI commands requires that an "appropriate default state" exists in the SPI input when uploading the programming signal via SPI output.  Unfortunately, neither Microchip nor PICAXE seems to know what defines this "default" state is.   Although the AD9834 is SPI compatible, it doesn't appear to have a signal to send to the SPI input of the PICAXE.   As previously indicated, the AD9851 is its own creature, and anything I do there will be improvisation.  I don't even know where to start - thus my posting.


I was wondering if anyone has attempted to interface with one of these DDS chips with a PICAXE.   I would prefer to avoid "bit-banging" as my interface is fairly intense. 


Thank you for your assistance.


Kevin G - WB0POH (not the same Kevin as the one named Kevin G)