A few weeks back I ran over this project, its purpose is to give dspbridge (or tidspbridge) users, a fair example of how to interact between a userspace application and a dsp dll, it is heavily based on dsp-dummy made available by FelipeC.
To be honest, I have never looked at dsp-dummy before this, but now I want to try writing a codec following this simple approach, although the result will be pure crap—coding and performance wise ;)—it seems like a good exercise.
In the mean time, other nice projects from the same Beagle Challenge can be found here.
BTW, if you ever run "SuperBeagle" project with TIDSPBRIDGE_WDT3 enabled, it may cause an overflow because of the way this dll was changed from the original dsp-dummy. Once it executes, the dsp side (dummy-dsp.c) falls into a while loop checking for messages all the time (NODE_getMsg with timeout=0) never refreshing the WDT timer... the common practice (on dsp side code) is to set the timeout value to infinite so the dsp can block that task and wake it up once a message arrives.