Is there a way to control this board with out the SDP card? From the schematics, it looks like Vdd and Vss only go to the output opamps. I want to run this independent of the USB bus and straight from our own controller using SPI. I do not want to power it using USB because the signal gets very noisy, especially when the computer is charging.
Yes you are correct. While the amplifiers and the reference is powered by the Vdd and Vss, the rest of the parts are being powered thru the 3.3V node. I cannot find any provisionary test point or connectors that would allow you to connect to the 3.3V node.
If you really want to (though I wouldn't recommend it), you may find a node to the 3.3V (maybe near U1) that may allow you to solder a solid wire just enough to provide the power needed by the parts and then use the data test points to connect the SPI lines.