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PICList Thread
'More on MIDI'
1997\12\08@224931 by Joe Little

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    I also have a MIDI project going on now.

    4 channel MIDI controlled light dimmer running on a PIC16C63.
    I can receive characters from a keyboard (thru a RS-232 to current loop
    adapter), read the AC zero crossings, read the dip switches, and dim the
    lights.... All the pieces work.  Anyone is welcome to all code and
    schematics with the understanding that it don't work yet.

    I have a demo version of a MIDI controller program called Cakewalk.  I
    can't see what's getting squrted out the MIDI output port because of the
    odd baud rate.   I have a MIDI book that explains MIDI commands, but I'm
    not sure that I'm getting across to Cakewalk, what I want it to do.

    I can add some Debug code to the PIC to buffer the Cakewalk commands then
    re-transmit them out at a standard BAUD rate to another terminal... But I
    can think of more fun things to do.

    Anyone know of a Windows terminal program that can work at 31250 Baud?????



    A few links to MIDI
    www.mediatel.lu/workshop/audio/fileformat/h_midiprim.html
    http://www.midiweb.com/hww/midi.htm
    http://Prairie.Lakes.com/~map/
    http://www.qns.net/paia/
    http://www.tpz.com/

1997\12\08@230330 by Andrew Mayo

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There is one (slimy) way to get a PC to look at MIDI. Take one standard
serial port card with either 16550 or 8250 UARTS. Replace the crystal.
Most of these boards will go to 38400 baud, from memory. You want 31250
baud instead. If I remember correctly, the crystal is 2.4576MHz and
needs to be 2MHz (it was several years ago, unfortunately). Then I cut
the tracks to the 1488/1489 line drivers and ran the output through a
6N138 opto and the input directly out with a pullup to +5. I just ran
the lines to the RS232 connector (yuk).

Now when you're running at 38400 you're really running at 31250. I can't
remember if I needed an invertor for the output or input line to match
the inverting line driver - I think I did need one, which I glued upside
down to the board (74HC04).

If you have a spare serial board, this is a cheap way to get a midi
monitor.

{Quote hidden}

1997\12\08@232016 by Ron Fial

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>     Anyone know of a Windows terminal program that can work at 31250
Baud?????
>
No, but here are two options.  Most any machine (pentium) nowdays is fast
enough that you can write a program to watch an input pin on the parallel
port (i.e. LPT1), and capture the stop bit and data bits at that baud rate.
Booting with DOS would make this task easy.  The PIC applications notes
will teach you how to code it.

Second option:  get an inexpensive Com1/Com2 plug in board for the ISA bus,
and change the crystal (somewhat lower value, easy to calculate), so that
when you tell the Com port to run at 38.4 kilobits, it really runs at the
Midi baud rate.


Regards,
 Ron Fial

1997\12\09@113054 by Mike Keitz

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On Mon, 8 Dec 1997 16:38:00 -0500 Joe Little <Joe.LittlespamKILLspamSCIATL.COM>
writes:

>     Anyone know of a Windows terminal program that can work at 31250
>Baud?????

Find an old serial (only) card and modify (midify?) it by changing the
crystal.  Usually a 1.8432 MHz or 18.432 MHz (with a 7490 divide by 10
between the xtal and the UART chip) is used.  If you replace the crystal
with a 1.5 MHz (or 15 MHz), then setting the baud rate to 38400 will make
the card actually work at 31250 baud.  The different crystal frequency is
invisible to the software.  OF course other options could be used.  It's
probably best to select a frequency lower than original so the UART is
certain to work properly.

Multi-function cards typically share the 24 MHz clock from the floppy
controller logic, dividing it by 13 to get 1.84615 MHz for the UART.  The
same kind of principle could be used, but of course the floppy controller
won't work properly without a 24 MHz clock.

1997\12\09@125857 by Alan Hall

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>On Mon, 8 Dec 1997 16:38:00 -0500 Joe Little <.....Joe.LittleKILLspamspam.....SCIATL.COM>
>writes:
>
>>     Anyone know of a Windows terminal program that can work at 31250
>>Baud?????
>

Some of the SMC Multi-I/O chips will do MIDI without any mods at all.

The FDC37C669 for certain is OK, but I believe maybe some of the earlier
SMC devices also.

You have to set a bit in one of the config registers following a special
procedure described in the data sheet (should be available from
http://www.smc.com). This changes the BRG input for the specified com port only
from 115200 to 125000 Hz. Then you just load the BRG in the usual way
with divisor '4' and bob's your uncle 31250 baud.

Most of the industrial PC cards use SMC chips (which is wot I'm doing)
but I think they are occasionally found in desktops and certainly in
multi I/O cards.

--
Alan Hall, Ipswich, UK
(01473) 652301

1997\12\09@140102 by Alan McFarland

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<x-rich>Hi Joe--


It seems you're already doing a portion of what I need to accomplish in a
project of my own- since you're offering, I'd love to see the schematics and
code for your project because I need to construct a digitally-controlled dimmer
using a PIC.  Where could I find your schematics and code?  Can you e-mail
them?


Frankly, I've found Cakewalk to be a little weird in how its implemented- it's
just kind of non-intuitive, especially when compared to a sequencer like
Vision.


As for your problem, I don't know of a Windows solution, but there are little
midi-tester gizmos at music shops that will read the datastream and readout the
sent code.  Another way to do it would be to build a little device like that
for yourself, using maybe a Stamp II and an LCD display.  The Stamp II can
send/receive at any baud rate up to 50,000 bps.


Hope this helps, and thanks--


--Alan McFarland



At 04:38 PM 12/8/97 -0500, you wrote:

{Quote hidden}

<center><bold><bigger>Alan McFarland's Applied Magic

</bigger>Custom Electronics for the Motion Picture Industry

</bold><smaller>Lighting and Electronics for Models, Miniatures, Props &
Sets


</smaller></center>http://www.appliedmagic.com
</x-rich>

1997\12\09@172525 by Herbert Graf

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-----Original Message-----
From: Joe Little <EraseMEJoe.Littlespam_OUTspamTakeThisOuTSCIATL.COM>
To: PICLISTspamspam_OUTMITVMA.MIT.EDU <@spam@PICLISTKILLspamspamMITVMA.MIT.EDU>
Date: Monday, December 08, 1997 22:52
Subject: More on MIDI


    I can add some Debug code to the PIC to buffer the Cakewalk commands
then
    re-transmit them out at a standard BAUD rate to another terminal... But
I
    can think of more fun things to do.

    Anyone know of a Windows terminal program that can work at 31250
Baud?????


   Easy answer, none. It is not up to the terminal program to determine
what baud rates are possible, it is the UART. To acheive a baud rate of
31250 you would have to change the crystal on an UART card. For example,
change the crystal so that a setting
of 38400 in the terminal program gives an actual baud rate of 31250. TTYL
and good luck.

1997\12\09@181140 by John Payson

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>     Easy answer, none. It is not up to the terminal program to determine
> what baud rates are possible, it is the UART. To acheive a baud rate of
> 31250 you would have to change the crystal on an UART card. For example,
> change the crystal so that a setting
> of 38400 in the terminal program gives an actual baud rate of 31250. TTYL
> and good luck.

While the PC's UART can't produce 31250-N-8-1, it's fairly easy to translate
38400-M-8-2 into 31250-N-8-1 using a PIC; no buffering is required since
the input and output rates, in bytes, are the same.  The only problem would
be that some MIDI equipment might not like having the stop bit get a little
bit shaved off; UARTs won't have a problem, but bytes will come in at a rate
of 3,200/sec instead of 3,125/sec.

1997\12\12@110724 by Joe Little

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    http://www.mindspring.com/~jlittle/picstuff.html

    I put my MIDI project there.  It's inprocess, and therefore not done yet,
    but not dead yet either.  I'm going to pick it up again tonite.  I haven't
    been insulted over the net yet, Maybe this will do it.  This is my third
    PIC project, and fifth embeded program.  Feel free to point out anything
    that could be done better.

    I don't feel embarrased by hanging this dirty laundry out... I must be a
    computer programmer.

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