[Coco] MM1 programmes

[KnudsenMJ at aol.com]

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.

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.

>  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.