[sdiy] Polyphonic keyboard scanner

[JH.]

No derision here.
The world's best, and yet unsurpassed, polyphonic keyboard scanner has been built from non-programmable logic ICs. (A pile of them, 
though.)
Look for Oberheim 8-Voice (or 4-Voice) schematics.
Never seen anything like that in software, or in programable logic, even though it would be *easy* to do.
Only drawback of that old circuit is that it wasn't designed to handle velocity and polyphonic aftertouch, but that would be easy to 
add, and it would probably all fit into a tiny FPGA.

JH.

----- Original Message ----- 
From: "David G. Dixon" <dixon at interchange.ubc.ca>
To: "'synth diy'" <synth-diy at dropmix.xs4all.nl>
Sent: Friday, July 31, 2009 6:52 PM
Subject: [sdiy] Polyphonic keyboard scanner


I know this will earn the scorn and derision of the programmers on the list,
but I'm wondering:  Does anyone here know of a polyphonic keyboard scanner
circuit based on logic IC's (non-programmable)?  Is this even feasible
without a massive pile of chips?  If so, I'd be very interested to learn
what the algorithm is.  The approaches I've been thinking about are all
fairly complicated (one scanner (counter + 2 multiplexers), but 8 separate
latches and ladders with data comparators to compare the count to the
latched data for preventing double latching and controlling note-off -- I
haven't worked out all the gory details yet).  I'd like to design something
that will send out 8 CV's, 8 triggers, and one gate.


_______________________________________________
Synth-diy mailing list
Synth-diy at dropmix.xs4all.nl
http://dropmix.xs4all.nl/mailman/listinfo/synth-diy