[Coco] MM1 programmes

[Gene Heskett]

On Saturday 15 November 2003 23:03, KnudsenMJ at aol.com wrote:
>In a message dated 11/15/03 8:46:27 PM Eastern Standard Time,
>
>gene.heskett at verizon.net writes:
>> I'd figured out a way to send some voices out one port, and
>>  the rest out the other.  Made for some weird stereo effects, and
>>  since neither of my keyboards take or output velocity, helped
>> with the realism a bit.  El cheeepo casios.
>
>Wow, dueling Casios!  The best I could do was to use the infamous
> "MIDI Y-cable" that Ed Hathaway made (or had Chris Hawkes making
> for him, ISTR).  This allowed the Coco rear serial port to drive
> two synths, even though the official MIDI spec said you shouldn't
> try to split the current loop that way.

I'm surprised the coco had the voltage, and the milliamp muscle to do 
that!

>Some of my better synths did have a MIDI Thru jack, so you could
> daisy-chain them in series.  But those early cheap Casios only
> received on the first 3 or 4 MIDI channels, so in order to get
> different notes on each one, you would have to use two independent
> MIDI ports like you did.  Cool.

They could receive on a group you could set, at least on the CZ-101.  
That wasn't the biggest problem for me, the limited polyphony was a 
much larger limit.  4 voices on the MT-240, and 8 (IIRC) on the 
CZ-101.  But IMO the 240 had the better sample set in it, spoiled by 
the cheaper audio.  If I was gonna do some more of that, I'd prolly 
go out to Wallys about Christmas and see about a 20 year newer 
keyboard, like one of those bigger, 88 key Yamahas with velocity. :-)

>>  But try as I might, I was never able to open that pack for
>> reading and I played the 500 monkeys scene for weeks trying to get
>> something back from my keyboards without generating a single
>> interrupt or data byte.
>
>I would gladly give away my old C and ML experiments in reading the
> Coco MIDI Pak under OS-9.  Some cute usage of such arcane notions
> as Data Modules and IPC for timing.  All of that worked, but when
> reading MIDI bytes, some would get dropped and some would get read
> twice (I think the duplicate bytes took the places of the dropped
> ones).
>
>I used my own scan loop on the Received Data Ready status line,
> rather than try to write a real device driver and get interrupts
> vectored to me.  Also I don't know that I was able to disable the
> interrupt from the MIDI Pak, so I always suspected that maybe some
> OS9 driver was getting the interrupts and stealing bytes out of the
> ACIA before I got to them.
>
>But on the MM/1, you could supposedly OPEN /MIDI for reading and get
> the bytes directly.  One reason I never tried was because I didn't
> want to play 500 monkeys with a soldering iron, trying to find
> which of the 7 remaining pinson the DB9 connector were the MIDI
> inputs.  And their polarities.  All this while not knowing if your
> SW is working, or is it your HW wiring?  I just avoid situations
> like that.
>--Mike K.

Thats where a scope is worth its weight in bottled beer, Mike.  Or the 
chips app sheet, and then trace the function lines to the connector.  

That, and the docs on the device, which for the coco rs232 packs was 
quite decent.  It's a shame the MM/1 didn't come similarly 
documented.  I never bought one, but if I had, I suspect I'd have 
been imitating Wayne Green, raising hell, and sticking a brick under 
one corner until I did get enough to work with.

-- 
Cheers, Gene
AMD K6-III at 500mhz 320M
Athlon1600XP at 1400mhz  512M
99.27% setiathome rank, not too shabby for a WV hillbilly
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by Gene Heskett are:
Copyright 2003 by Maurice Eugene Heskett, all rights reserved.