Arduino AD9951 VFO Project Update

Arduino AD9951 VFO Project Update

I am incredibly excited to announce that I’ve received my Arduino Mega AD9951 VFO design back from the fabricator and I have finally had a chance to assemble it. What’s more is that the darn thing actually works! Who would have thought?!?!

Please visit the Arduino VFO using an AD9951 DDS project page for further information about this project.

I made a small mistake on the first version of the board, which was that I routed the power for the 3.3V regulator to the wrong location. That, and I was not happy with how the TPS regulators from Texas Instruments were working out so I decided to simplify the design.

I also had the SPI mode for the Arduino configured incorrectly; the SPI mode that the AD9951 chip wants to see is apparently Mode 3, with MSB first.

While I don’t own an oscilloscope powerful enough to view a waveform above a few hundred kilohertz, I was able to verify that my shield is working by sending it first the 10KHz tuning word, followed by the 100KHz tuning word, and then the 250KHz tuning word. After sending the appropriate tuning word, I was able to see the waveform and verify the frequency. The amplitude is quite low, about 0.140Vpp, but I think that may be due to the filter that I’m using. I am going to try to take this to work and use a real oscilloscope to see what else I can do with this shield. I’m incredibly happy particularly because I wasn’t certain that this shield would work.

I have updated the library for this Arduino and AD9951 combination so you, too, can build a shield and test it with my code. You will also find an example. All of this code is still beta, and is far from complete at this time. I will be expanding it over the next few weeks.

Please visit the Arduino VFO using an AD9951 DDS project page for further information about this project.

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