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Conference hydra::amiga_v1

Title:AMIGA NOTES
Notice:Join us in the *NEW* conference - HYDRA::AMIGA_V2
Moderator:HYDRA::MOORE
Created:Sat Apr 26 1986
Last Modified:Wed Feb 05 1992
Last Successful Update:Fri Jun 06 1997
Number of topics:5378
Total number of notes:38326

2894.0. "MIDI RELATED PROBLEM" by POLAR::GOSLING () Tue Sep 05 1989 10:20

       This may belong in the MIDI notes conference, but I know and love
       you folks, so I thought I would ask the question here first.
       
       I just built a midi interface (Amazing Computing vol 2.2).  Simple
       enough to do, although my soldering skills are not up to what ever
       the DEC standard is.  Hooking it all up, I am able to get my AMIGA
       (A1000) to talk to my keyboard (CASIO CT-640), but can't get the
       keyboard to talk to the AMIGA, as in entering notes onto a DMCS
       score.  I also tried some of the MIDI related tools from various
       FFish disks with the same results - AMIGA can talk to the
       keyboard, but not vica versa.  I have gone over the MIDI IN
       circuit a thousand times and can't find any problems in my wiring,
       soldering, etc.  I even replaced the IC thinking maybe I popped
       it.  I am therefore a bit suspicious (grasping at straws perhaps)
       that my keyboard OUT itself is at fault.
       
       Could anyone tell me what the electronic characteristics of the
       OUT signal are.  In other words, if a put a meter on pins 4 or 5
       and ground of the OUT connector and press a keyboard key, what
       should I see in terms of a meter reading.
       
       Thanks in advance for any assistance.
       
       Art
T.RTitleUserPersonal
Name		DateLines
2894.1Me tooLOWLIF::DAVISThat's not a BUG, it's a FEATURE!Tue Sep 05 1989 12:2310
Art,

I have a CT-640 also and have had times when I see exactly what you describe.
I think I always moved the mode switch back off the MIDI setting, powered off
and back on, and switched back into MIDI and it worked.  This has happened a
few times and it was always solved by switches on the keyboard.

Proabably not your problem, but I thought I'd mention it...

...richard
2894.2SAUTER::SAUTERJohn SauterTue Sep 05 1989 13:417
    I've never looked at it, but I think it's a current-loop signal.  To be
    sure, look at the transmit wires, then move to the receive wires and
    look for the same indications.  The signalling speed is 31,250 baud,
    so you may have to look quick.
    
    The real information is in the MIDI standard, of course.
        John Sauter
2894.3PROBLEM UPDATE - STILL A PROBLEM!!POLAR::GOSLINGThu Sep 14 1989 18:1343
       As an update, I am going around and around with this problem.  I
       thought perhaps my CASIO (CT630 not CT640) had a bad OUT circuit,
       but hooking it to another keyboard proved me wrong.  I also built
       another MIDI interface (the latest AMIGOTIMES) which provides for
       only one IN and one OUT circuit.  Real simple stuff - none of the
       passing the serial port, thru's, extra IN's, extra OUT's,
       switches, etc., that the AMAZING Computing MIDI interface I built
       first has.  Bottom line, is that I have exactly the same problem
       with this 'new' interface as the problem referenced in the base
       note with the first interface - AMIGA can talk to the keyboard,
       but keyboard can't talk to the AMIGA.
              
       Brien Roscetti, an A500 MIDI aficionado :-), has been kind enough
       to volunteer to assist me in checking out my interface on his
       spare A1000 and to apply his technical talents to debugging it (he
       has been considering building an interface for his A1000, so this
       will give him an opportunity to try one out).
       
       One thing that comes to mind (and given Brien's main AMIGA is his
       A500 he was unable to comment on), is the A1000 problem associated
       with too many 'hang ons', the need to ground PALS, etc., etc.
       Could this be causing my problem??  I'm grasping again.....
       
       My configuration is as follows:
       
       - A1000
       - 512k internal memory.
       - 2meg Micron (ASDG) board on the side (powered by its own P/S)
       - Wedge driving an RD53.
       - LA75P on the parallel port.
       - Scholar (when I'm not trying to get this $%#@ midi thing working)
         on the serial port
       - Internal and external 3 1/2" drive.
       - 5 1/4" drive (with its own P/S).
       
                Note that the serial port WORKS FINE with the Scholar.
       
       If anyone has any thoughts, I would again appreciate hearing from
       you.
       
       Art (who wishes sometimes he lived closer to the GMA when problems
            like this arise)
2894.4PROBLEM SOLVED - AT LAST!!POLAR::GOSLINGWed Oct 04 1989 16:0820
       Just a quick one to close off this note, as well as to publicly
       express my gratitude to Brien Roscetti.
       
                             THANKS AGAIN BRIEN!!!!
       
       Through Brien's efforts (I apologize Brien if I am misquoting or
       misrepresenting you at all), the problem was isolated to the 220
       ohm resistor on the input circuit.  While this resistor provides
       protection to the circuit against a crosswired MIDI cable, it also
       offered just enough resistance to stifle the signal from the CASIO
       keyboard (keyboards actually, because I tested it with a couple of
       flavours of CASIO, as did Brien) to the AMIGA.  The problem became
       apparent when the interface worked fine with Brien's Yamaha
       keyboard(s), but not the CASIO.  When the resistor value was
       lowered, the CASIO worked!
       
              Who would have thunk it would have been that simple!?
       
       Art