dac/adc/usb example might be interesting read

I found an example "sketch" for a sam3s,
but I feel the code is instructive for the Due as well.
I do not expect this to run on a Due.

it shows the dac and adc being driven by a timer, and consuming/producing
arrays of data by using the PMC dma.
for me this solved how to run DAC and ADC in parallel.

http://www.at91.com/component/resource/article/Academy/43-Hands-on/1197-sam3s-ek-phone-demo.html
just use the zip file, the separate pdf is the wrong one.

This can be done also on the Due but it is a bit touchy regarding hardware. You can be inspired by the SAM3S-EK schematics to reproduce the system on a proto shield.

As far as I know, SAM3X and SAM3S share a very similar ADC and DAC... :wink: