MIDI-SYNCH (was Re: simple MIDI?)

Stopp,Gene gene.stopp at telematics.com
Mon Jan 19 23:40:00 CET 1998


Old PC's work great for MIDI projects. You can make a MIDI-CV converter
by controlling a DAC on the parallel port and using a standard MIDI
MPU-401 compatible sound card. You can write the software in whatever
language suits you - I find it easiest to just use QuickBasic because it
already comes with DOS and there are no compiler requirements. It can
keep up pretty well for "normal" MIDI-CV algorithms but if you want to
get real fancy then you're probably better off writing in C and
compiling. There's really no reason to run Windows at all (especially
95) - DOS 6.22 is probably good enough. Just get a cheapo hard disk and
stick your program in AUTOEXEC.BAT. You can probably find 30-40 Meg HD's
that people will PAY YOU to take.

For the MIDI interface there are lots of sound cards out there that you
can buy brand new for less than $20. Buy it for the MIDI interface and
get audio for free. If you really want to hack around you can use an old
style serial card for the MIDI ports (the kind with discrete UARTs, not
ASIC emulations) and swap out the crystal to get 31.25 kbps. I forget
the actual crystal values, but it's in the DIY archives somewhere. If
you go this route you'll need to modify the physical interface to
current loop instead of RS-232.

I personally plan to build a whole bunch of embedded PC MIDI projects -
I've got such a stockpile of PC parts that I can stay busy for years.
The stuff is worth close to nothing, except as great project parts.
386's and 486's are perfect for dedicated MIDI processing.An 8088 might
be too slow, unless you compile your code to an EXE.  My wife's ex used
to work next to a PC repair shop, so he would bring over bunches of
perfectly good 386 and 486 motherboards (even a Pentium once!) that he
got OUT OF THE DUMPSTER. No kidding. Good CMOS and everything. I was
lucky enough to "inherit" a few SVGA monitors and keyboards when the
plant closed at my previous job, so I'm pretty well stockpiled now.

So with all this talk about microprocessors and flash and EPROM burners
and assembly language, it may be useful to point out that embedding a PC
in a project is a very powerful option these days, for the same kind of
dollar investment, but with an operating system and user interface
already there! All you need is enough room for the motherboard and power
supply. Hopefully there will be some analog stuff controlled by the CPU,
so there should be plenty of room inside because of all the knobs on the
box, right?

Some of my crazy project ideas:

* Putting a PC inside a homebuilt synthesizer for keyboard scanning and
patch storage
* MIDI clock/sync to voltage clock pulse converter (with the parallel
port)
* A MIDI Note-On generator for my Moog Drum (using a joystick port)
* MIDI bass pedals

I've already got an 8-channel DAC with MIDI control on a 486, hooked up
to one of my modulars. It is fantastic. I think the emails which
describe my construction details are in the DIY archives as well.

BTW - got another darn Pentium (for the family, kid games, scanning,
etc.), and I'm wondering if there are any suggestions for a sound card.
I don't really need the best out there, just a good one for the money.
The machine will NOT be used primarily for synthesis or recording, but a
wavetable or FM synth daughterboard may be OK if it really makes a big
difference. What's good out there these days? Emu, Kurzweil, Turtle
Beach, Creative? Top price would be, oh, call it $200. Any ideas? TIA.

 - Gene
 ----------
From: POLARIS at vax1.mankato.msus.edu
To: synth-diy at mailhost.bpa.nl
Subject: Re: MIDI-SYNCH (was Re: simple MIDI?)
Date: Monday, January 19, 1998 2:21PM

Colin wrote:

{Using a microcontroller is not much more difficult, but a lot more
equipment is needed to develop code, program roms etc. than to hardwire
a UART.
What I found easy, and cheap, is to get a late 1980's home computer with
a decent user port, and build a midi interface plus analogue/digital
input/outputs as an add on.}

Could someone provide info as to how to do this with an old IBM-clone
PC?
I have a few 8088-based machines, and a couple of 386 machines lying
about.  Are there texts that would be helpful in turning a PC into a
dedicated MIDI controller - maybe a MIDI->CV converter?



Dave



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