AD/AD conversion

Short answer NO. Long answer - still NO. But, interestingly, D/A converters are often used to create A/D converters.

You cant do that actually, check the circuit diagrams for AD and DA converters they are completely different. Well you can always operate and re arrange the components.

Thanks, All.

an easy way to make a dac would be to use your micro to PWM and use a low pass filter. change your duty cycle to change the DC voltage out of your low pass.

No you need a D/A of the same bit size.