I am using only the DMA interface of the FMComms3 design. During times when I am not streaming, there are tones in the RF output coming from the DDS block within the 9361 IP core. I can disable the DDS with the following command and then the tones disappear:
echo 0 > /sys/bus/iio/devices/iio\:device3/out_altvoltage0_TX1_I_F1_raw
However what I really need is some way to set the default DDS configuration so that nothing is ever transmitted from the time that I power up the board. The only time it is acceptable to output any RF is when I am streaming via DMA. Where is the DDS configuration stored and is it possible to prevent the DDS from being started in the first place?
I am also aware that there is a mux in the 9361 IP core which selects between the internal DDS and the DMA interface. In the future I plan to have a custom HDL modulator in place of the DMA block. How can I control this mux so that it reads IQ from the custom HDL instead of the DDS? If it is possible to permanently set this mux to DMA then perhaps I do not need to disable the DDS in the first place.