[sdiy] Polyphonic keyboard scanner

[Carsten Tönsmann]

I did this, and it is madness. It was a polyphonic approach, but worked 
stable only in monophonic mode. It is possible, of course, but I DON'T 
RECOMMEND IT, due to this experience.

Please look at the tiny little board around an AT90S2313 I built for an 8 
voice polyphonic MIDI scanner for a 61 key keyboard:

http://www.analog-monster.de/kbd_new_en.html

This scanner does not provide velocity information, just plain key infos, 
but I've just finished a new 10 channel keyboard scanner with velocity 
information and joystick, documentation will follow. Using a microcontroller 
(or an FPGA) will enable to add / change functionality or handle errors PER 
SOFTWARE, without heating the soldering iron. I am not good enough in 
electronics to omit software issues in such complex boards / modules, so I 
decided to use both hardware and software to solve those problems.

Carsten
http://www.analog-monster.de/index_en.html


----- 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