I am looking for a solution that will allow the user to change actively the DAC clock rate (analog output rate). for example: if the user enter 48000 the analog output rate will be 48 kHz.
second issue is how the user enable/disable using serial commands on of the DAC ports.
third issue is the ability to write arbitrary waveform to one of the analog output. for example: chirp or amplitude modulation which are defined by basic mathematical formulas.
Generating waveforms is not just a question of software but also hardware. You will need to filter the output to create the final signal. Could you let us know whether you have already consider that part?