Interfacing Directly with the OMAP3 DSP over SPI for a PID Feedback System

I am a graduate student in Physics interested in building a 'homebrew'
electronic servo for one of our instruments (a scanning tunneling
microscope). I am researching possible solutions for an embedded
platform which combines the speed and vector-based calculation power
of a DSP for electrical servo'ing (Basically a PID feedback loop:
instrument output -> ADC -> OMAP3 DSP via SPI -> DAC -> instrument
input), with a linux server for data collection. I have been reading
about the Beagle Board and I think it might be the solution I need for
this project, but I am lacking some fundamental understanding on the
device architecture.

For this project it is necessary to communicate *directly* with the
OMAP3 DSP via serial. Once programmed, the DSP would then handle the
servo/PID loop (see above) asynchronously from the ARM processor. In
other words, the DSP would handle the most basic functionality of the
microscope (servo/PID loop, or Part I), while the ARM processor would
be used to collect/store data and to change the different modes that
we could run on DSP (Part II).

After reading through the documentation, I am still unsure as the
whether this possible with the Beagle Board. The documentations
frequently mentions the "DSP Bridge" or "DSPLink," which I take it are
drivers which allow for interfacing between the DSP and ARM processor.
This functionality would satisfy Part II of my project. However, it is
unclear to me whether it is possible to communicate with the DSP
directly via SPI (or any other kind of serial interface). Is it
necessary to communicate directly with the DSP because of the speed at
which my instrument operates, and I would like the instrument to
continue functioning even if the operating system crashes.

I understand this is a newbie question so thanks for any help you can
provide.