MIDI controlled SID, was flying faders, was [sdiy] keyboard resources

[Bill Keys]

Well, one reason is that the C64 doesn't fit into my rack very well. ;o)

Also, I wrote a book a number of years ago, called "Music And Sound For The 
Commodore 64" - so I know what a b*tch it is to program the SID via the 
C64's basic interpreter. Just not flexible enough to create the more 
exciting sounds. I even used DATA statements to load in short machine 
language segments for a program or two in the book. Still too painfully slow 
from an operational (setting up) standpoint.

No real-time control, other than the POTX and POTY 8-bit (joystick) ports. I 
don't think the keyboard does much to help, controller-wise. Forget about 
taking the ADSR or waveform samples from the SID register and popping them 
back into a filter reg... too much code effort for too little gain. Same 
with going from the POT ports back into the SID. The 6502/6510 was running 
at only 2 Mhz. That whopping 65535 bytes gets eaten pretty fast, too.

Of course, you might have MOD software lying around, but I think most of 
that doesn't take advantage of the synth, as much as it does for providing a 
way to playback the music.

Plus needing a monitor in the rack....

I'm leaning towards using the 10Mhz (or is it 20Mhz?) OOPIC 
(http://www.oopic.com) as a controller for a SID-based unit, myself. some of 
the things I've been considering...

MIDI-To-SID converter: take a midi note number and look up the hi and low 
frequecy values to pop into the SID.

PIC DCEGs: Digital Complex Envelope Generators, keyed from the same source 
as the SIDs gate signal comes from. Provides data to pop into filter regs, 
frequency regs, etc.

The OOPIC has 4 8-bit A/D converters, useful for hooking analog things to, 
then routing the digital value to the SID - selectable from the panel and 
sent to filter, frequency, waveform selector, pulse width setting, etc. 
Can't do any of that as easily with the SID chip stuck in its C64...


>From: "John L Marshall" <john.l.marshall at gte.net>
>
>The "Commodore 64 Programmer's Reference Guide" has 25 pages dedicated to
>the 6581SID.
>
>I am unclear as to why people are building dedicated single board computers
>to control the SID. A single board computer already exists with plenty of
>RAM, ROM and I/O. The processor is a popular but mature 8 bit type and it 
>is
>easy to program. This single board has enough speed and power to program 
>the
>6581 in realtime.The addition of MIDI I/O has already been done. I'm 
>talking
>about the Commodore 64. Cheap and plentiful.
>
>
>----- Original Message -----
>From: John Lamb <jlamb3 at nc.rr.com>
>To: <synth-diy at dropmix.xs4all.nl>
>Sent: Tuesday, August 28, 2001 12:53 PM
>Subject: Re: MIDI controlled SID, was flying faders, was [sdiy] keyboard
>resources
>
>
> > "Andrew Martens" <amartens at interchange.ubc.ca> wrote on 8/27/01 9:42:19
>PM:
> >
> > >That reminds me, I need to get to work on my SID synth again...
> > >
> > >Cheers,
> > >Andrew Martens
> >
> > I'm interested in doing something similar -- If you could point me 
>towards
>some good 6581 documentation I
> > would be much obliged.
> >
> > Thanks
> > John Lamb
> >

+_+_Yes, honey, I know there are 25 boxes of electronic junk cluttering up 
the attic. They will, one day, magically be transformed into a modular 
synthesizer cluttering up the attic.... www.mp3.com/OriginalSimulacrum _+_+



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