I got the FMCOMMS1 development kit working with the ML605 board. I get a nice sine wave display on ChipScope connected to the output of the ADC pcore. However, when I attempt to lower the amplitude of the DAC pcore DDS generated sine wave to anything below full range, I get distortion and dc offset on the ADC output. The output is not predictable, if I power cycle the board the waveform and DC offset changes to different value and shape.
I am only changing the amplitude of the DDS. I verified that the DDS is outputing the correct amplitude using ChipScope connected to the DAC DDS output..
What is causing the distortion and DC offset when the amplitude is lowered?