From: bobhays@spss.com (Bob Hays)
Subject: Re: MIDI-CV converters/MIDI-CV sync designs
Date: Mon, 06 Apr 1992 18:06:18 GMT
Organization: SPSS, Inc.
Keywords: sync, convert, MIDI, CV, analog, hardware


In article <u894825.702536276@bruny>, u894825@bruny.cc.utas.edu.au (Jon Elliott) writes:
> Does anyone have any ideas about how to build MIDI-CV converters or MIDI-CV
> sync generators.  I've got a vague idea.  Simply summarised, it's an EPROM
> based ASM design coupled with a MIDI IN and THRU connection.  The algorithm
> (after we have our data) is as follows (for a sync generator):
> 
> 	1.	Get byte.
> 	2.	Is it a MIDI clock signal.  If not, go to 1.
> 	3.	Increment counter.
> 	4.	Is counter equal to x (x = 6 for 1/16th note sync).  If not, go
> 		to 1.
> 	5.	Send out sync pulse.
> 	6.	Reset counter.
> 	7.	Go to 1.

Should be right

> 
> For MIDI-CV conversion, we abandon the counter and the algorithm becomes m
> complicated as we convert note numbers to voltages and send them out via a
> DAC.  With the sync generator, we have no such problem as we can simply
> digitally trigger (using logic-level voltages) a switch to send out a +5V
> signal of an arbitrary width.
> 
> Anything wrong with the idea that I have?  I heard that Metlay was working on
> similar stuff so surely plenty of netters have at least a vague idea.

Just remember that you might have more than one input voice (or do you
plan to force only one note on one channel at a time or to take first
note/last note priority....).

> 
> Oh, I also need a MIDI merge box.  Are these easy to build?  It seems to me
> that you need some pretty smart thinking in order to slip miscellaneous data
> into the stream coming from, say, a sequencer.  What I'm trying to do is
> run a line of an Ensoniq EPS to a mini keyboard so that a DJ can trigger
> samples from it while also using the EPS itself to play live and sequence.
> The block diagram of this arrangement is:
> 
> DJ-----------------------------------------------|------------------|
> Sequencer----------------------------------------|MIDI Merge        |------
> EPS's own kbd (or master controller)-------------|------------------|     |
> 					^			          |
> 					|				  |
> 					|---------------MIDI IN---------->|
> 									-----
> 									|EPS|
> 									-----
> 
> I am also going to have to use a similar arrangement with some drum pads.
> Hence, is this easy to do?  If so, how?

If you don't mind building, _Electronic Musician_ ran an article about
one year ago on this very subject, with schematic and EPROM code
source.  It used, I think, a 68xx all-in-one controller chip.

I'm responding because I am seeking something simpler - a 4 to 1 MIDI
switch.  I'd like it to indicate what channel is switched to which
output.  It does not need to talk MIDI at all (just have the
connectors and a switch in the middle), but I haven't found sources
for a four-throw, three (or four) pole rotary switch lately, so a
digital switch circuit, counter, numeric display and LED seems more
likely, but harder for a non-EE like me to design.  Anyone seen a
schematic of such a beast (or, a multipole switch based in digital
electronics with numeric readout would help).

Have fun! - Bob
--
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