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Output frequency on AD9910 using external control

Question asked by ramola on Mar 10, 2015
Latest reply on Mar 13, 2015 by mcee

Hi,

 

I am using an AD9910 evaluation board and a FPGA to control it. I plan to output a given frequency from the board and then use the parallel port to modulate the phase. So I used the SPI command to enter the frequency tuning word and then using an if else statement I switch to the parallel port. I am stuck on the first step. I cannot generate a frequency from the DDS. I have made all the connections required to control the eval board externally. Once the connections are made I use the FPGA to send data to the sdio pin. Since first I want to at least be able to generate a frequency using SPI, I have turned the parallel data port enable bit off. I address register 0x07 to change the FTW and 0x09 for the amplitude scale factor. All other registers are at their default value (which means RAM and digital ramp are both off). Am I missing something). All the pins on header U9 are set to LOW and I am measuring the output at filtered out (J4). The output works well when used with the eval board software (with the respective jumper connections)  Any help would be appreciated.Thanks!

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