Hi netcien,
Since your post has over 100 views and still no answer, I'll attempt one though not a miniDSP user. Generally the best way to connect SigmaStudio to a SigmaDSP sitting on any custom board is to first see if that board has, or can be made to have, a 10-pin header wired like this (from the ADAU1701MINIZ schematic diagram):
This is where you would connect an Analog Devices eval-adusb2ebz (a.k.a USBi) for communication with SigmaStudio on your PC. There's several advantages to this "orthodox" method, not the least of which is it allows for SigmaStudio's interactive tuning and read-back features to work. This sure beats the old "burn, crash, and learn" technique. The USBi is available at: http://www.analog.com/en/design-center/evaluation-hardware-and-software/evaluation-boards-kits/eval-adusb2ebz.html#eb-ov…
Also refer to Application Note AN-923.
Best regards,
Bob