SPI Connections to DAC
I'd like to output something simple like a digital AC voltage to the DAC and have it convert it, but as I understand it from here, I am just using the digitalWritecommand which is basically binary. How do transfer something more complicated to have the DAC convert it?


SPI is a communication protocol.  It uses digital signals, coupled with time, to transfer information.

To use DSPI you need to first define an SPI object

DSPI0 SPI;


From then on it's the same as using the Arduino SPI library.

Start it

SPI.begin();


Then transfer the correct commands (found in the DAC datasheet) to set the voltage of the output

digitalWrite(10, LOW);
SPI.transfer(0x43);
SPI.transfer(0x1A);
digitalWrite(10, HIGH);


The values there are just examples. The 10 is the chip select pin for the DAC, and the values used in the transfers (however many are needed) need to be found in the datasheet.

If you only want to use the pins associated with DSPI0 you can use the SPI library instead (which only supports one SPI channel - the uC32 has two), in which case it is identical to working with the Arduino SPI library.


  Likewise, how do I get the DAC to do the reverse, ADC, where it reads in a voltage and sends the Arduino a digital signal through SPI pins?


You don't. DACs are DACs and ADCs are ADCs. They aren't interchangeable. 

For ADC functionality just use any of pins A0 through A11 and the analogRead() function.