SynthModules

I was sitting here looking at my latest module which is a conversion
of the PAiA MIDI2CV to a MOTM format.  I had it left over and thought
it would get more use installed in my synth.  Then it dawned on me ...
I could use this for a PSIM expansion.  Mode4 in the PAiA is a MIDI
Control Change to CV for all 8 channels.

I can expand the PSIM by up to 8 CV channels out by using the MIDI
output capability of the PSIM to send Control Change messages to
the PAiA.  The PAiA only uses 7 bit data so the outputs have less
resolution over the 0 to 10 volt range.

The PAiA implements running status so it's only two bytes of data
per channel which takes ~615 uS to transmit in polled mode.  This
may be that excuse for me to update my MIDI drivers with interrupt
driven transmit.

Right now I have the PSIM looping all 4 inputs to outputs and
generating an 22 Hz 5 volt ramp output on the PAiA output with
additional 5 mS triggers on output 2 and output 3 that occur at
33% and 66% of the duty cycle.  Neat!

Dave