The Black ADF4351 Boards

 Well,

Some time ago, I did some expermimentation with black ADF4351 evaluation boards that are available at all good sites selling wares from the land where copyright means "lets copy it right".

I've bought some more recently and found that I couldn't get them to work.

Thanks to this post, I was able to deduce that the newer boards seem to be missing some bits - most importantly the CS line isn't tied high by a SMD resistor. Once I had pulled that pin high via 10K to the 3V3 line, the board worked as expected.

I've been using mine with a Pi Pico2:

You can see the additional 10K on the fritzing diagram above.

I have written some very simple code here to upload the register values to the device, and also have a spreadsheet here that will do the necessary maths from a target output frequency, channel spacing and clock frequency and generate the 6 register values needed to program the device.

Good stuff!