ADDAC506B VC Stochastic Function Generator Expansion

Inspired and officially licensed from Teia's Stochastic Function Generator which was introduced in 2013 but is no longer available. We used the concept of the early version but completely rebuilt and reprogrammed it's mcu to a fully featured 4 voice 2 stage envelope and slew generator.

This expansion allows extra I/O to our ADDAC506, namely:
 
Four trigger inputs for the random engine.
Four CV random outputs from the random engine.