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AD9956 Write Serial Port, Timing Issue?

Question asked by joshua.alper on Aug 5, 2016
Latest reply on Aug 10, 2016 by joshua.alper

Hello,

 

   We are trying to send a signal to an oscilloscope from the AD9956+PCB. We have a 2.4Ghz VCO attached to the DUT via DUT RF_IN, and we have checked that it is outputting a signal using the USB software via the DUT FILTER OUT. We then switch to using the serial port, and try to send info the the DDS via an FPGA. However, when we run our program we are getting nothing. We have checked the FTW we are sending prior to the loop that starts sending the info from the FPGA to the DDS, and it matches our hand calculations. We also checked the address, and it is correct as well. We attempt to send it to PCR0, so we make sure to wire PC0-PC2 to 0-0-0 so as to read from PCR0. Is this incorrect?

 

We do not believe this is incorrect, we believe it is a timing issue. The AD9956 data sheet has two figures, 33 and 34, which explain writing via the serial data port. Can someone please explain the timing to us? What order do you have to arrange the data transfer and SDCLK switching to successfully write to the DDS? How about for reading? I will attach screen shots of our program, please feel free to point out any issues in our logic, but we are fairly certain we are suffering from a timing issue. Thank you in advance!

WriteToDDS_1.pngWriteToDDS_2.pngWriteToDDS_3.png

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