MIDI Decoder Chip?

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  Is there an IC that will decode MIDI data?  I need something that I
can use in an embedded system with a fairly simple (e.g. 8051 or PIC)
microcontroller.  Ideally the chip would take MIDI data directly and
output analog audio for an amplifier, run on 5V and be available retail
in a thru hole package, but I'll take what I can get :-)  It does have
to be something I can by retail, though, in small quantities.

  I know there are MP3 decoder chips (e.g. the STA013) that approach
this ideal, but I really need to play MIDIs, not MP3s.

Thanks,
Bob Armstrong


Re: MIDI Decoder Chip?

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i say either a basic synthesiser chip, or read the midi spec farther than  
the first half page.  try midi fanatics brainwashing center, it'll  
probably help you.

--
Using Opera's revolutionary e-mail client: http://www.opera.com/mail /

Re: MIDI Decoder Chip?
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MIDI Is a standard of controls and notes. It does not dictate instrumentation.
MIDI Is like having the sheet music to a song. It has no inherent sound. What
you need is a sound synthesizer that understands MIDI and can generates sound
based upon it.

There is a standard called "General MIDI" which puts specific instruments on
specific channels and patches, but you really need to understand what your MIDI
source is set up for to know what it's going to play. I have MIDI files I've
created from my own sequences, but you can't play them back on anything other
than my studio (no sounds will be correct).

-->Neil

Re: MIDI Decoder Chip?
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Yes, It's called an UART.

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Practically all microcontrollers have at least one UART built in,
so you're not likely to need anything but your microcontroller
and an electrical interface  for the 5 ma current loop (use e.g.
a 6N138 optocoupler).

DJ
--



Re: MIDI Decoder Chip?

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I think you completely misunderstand what MIDI is.  MIDI is just the
information a MIDI keyboard generates when you play it - i.e. note on, note
off information and things like the continuous data output of a pitchbend
wheel.  It is "button press" information, not audio.  Put this information
into a MIDI equipped sound module and then you will get sound.

If you want to receive this information with something like an 8051 it is
quite easy using some buffering/opto-isolator circuitry.  Search the web for
this, there is loads of information.  You will also find various MIDI
routines you can use or adapt, depending on what you want to do with the
information.

Gareth.



Re: MIDI Decoder Chip?

  I'm sorry for not being clear, but you guys misunderstand - I don't
want to control an external MIDI synthesizer.  I want a MIDI
synthesizer chip that I can build into a project.

  Think of a cell phone - most phones these days can render MIDI ring
tones.  I need something on that level.

  Yes, I know that many MIDIs will end up sounding like cheap elevator
music (or a cell phone!) when rendered this way, but that's OK.

Thanks,
Bob


Re: MIDI Decoder Chip?
P.S.  Something like the Micronas MAS3505G is an example of what I'm
talking about

http://www.micronas.com/products/documentation/consumer/mas35xyg/index.php

EXCEPT a) I don't know of any retail source for this chip in unit
quantities, and b) it's only available in a BGA package which I
couldn't solder even if I had one!

Thanks again,
Bob


Re: MIDI Decoder Chip?
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Winbond do one, W56964 which is a 34 pin QFP, general midi synth
including a power amp, but I have no idea where you would obtain them in
small quantities.
--
Tim Mitchell

Re: MIDI Decoder Chip?
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I found these chips that are still in manageable DIP/SOP packages:
http://www.holtek.com/english/products/mcu_5.htm

Not sure if they have distributors where you are.

/Rolf

Re: MIDI Decoder Chip?

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Well, suffice it say it might have helped if you had asekd for a
synthesizer chip right away, instead of speaking about a "decoder"
chip.  Acquiring anything like that in qty less than 1000 might indeed
prove challenging, these days, when most applications, including
cellphones, would just use a DSP and a huge wave table memory instead
of dedicated chips.

--
Hans-Bernhard Broeker ( snipped-for-privacy@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

Re: MIDI Decoder Chip?


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DSP is an overkill.  UART is unnecessary.  Just use a DIP micro with
timer/counter.  You can just program it to change the tone/frequency
every few msec.  However, you do need lots of external data storage for
the wave table.  If I were you, I would use an 40 pins DIP AVR hooking
up to a Compact Flash.  If you need it, I can send you a simple layout
for it.  The rest is just software.

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Re: MIDI Decoder Chip?

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'Just software' sounds like software is easy/trivial and hardware is
difficult while it's the other way round.

Jeroen



Re: MIDI Decoder Chip?


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Both hardware and software are relatively easy.  You can probably
wire-wrap a board in a few hours.  Take a ATmega 16 (40 pins dip) AVR.
Hook up one of the Port A PWM output to a low-pass filter (RC) and
speaker.  Port B & D to the Compact Flash data bits.  Port C to the
control bits.

Setup time 1 to output PWM tones and time 2 for the durations.  Keep
feeding the timers from the Compact Flash wave table.

Should cost less than $20 dollars total.

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Re: MIDI Decoder Chip?
If you really don't want to implement the synth in software, I think
maybe the really old soundblaster-type cards had a midi synth chip of
some sort that you might be able to desolder and re-use (you want
something before the board went to being just one asic).  You'd
probably have to have a micro to get the data between the actual midi
interface and the chip, since it's probably expecting to be fed over
the ISA bus.

Oh, the old chip will no doubt sound terrible since it will use FM
synthesis rather than a wavetable.  But then homebrew software might
not sound so great either.

On the positive side, big flash devices are fairly cheap now, so
wavetables are practical in a microcontroller implementation.  You
might want to use a DSP-flavored micro with lots of helpful
instructions and a hardware interface to common serial audio DAC's.


Re: MIDI Decoder Chip?

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You might try Yamaha. They used to have a range of synthasizer chips
which might still be in production. There might be an obscure Far
Eastern second source which still produces the devices for niche
markets. People in the retro-computer scene might be able to help.
(Old Ataris, Commodores etc. often had add-ons that contained these
synthesizer chips)

Regards
   Anton Erasmus



Re: MIDI Decoder Chip?
In comp.arch.embedded,sci.electronics.components, On Thu, 16 Jun 2005

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   Do these chips actually accept MIDI commands directly? The chips I
recall from years (okay, decades) ago were parallel-interface
peripherals for a microprocessor bus (such as the C64's SID chip and
earlier GI AY-3-whatever used in arcade video games). These used the
computer's main processor to decode the MIDI commands and put the
proper values into the sound chip's registers.
   I suspect even in a cell phone the MIDI rendering is in software.
There was at least one hardware implementation of MIDI (Roland TR-707
drum machine used lots of CMOS logic), but with MIDI-capable
microcontrollers for a dollar or less, it only makes sense to use one.
   There's also exactly how much MIDI functionality you want. The
original MIDI spec is just receiving note-on and note-off commands,
and playing and stopping each note as the appropriate command is
received, but there's also MIDI File Format, where you have a file
(under most OS's, the extension is .MID) that has a whole song
(note-on's and note-off's, but also the timing between these is
encoded in the file), you would send the file to the chip and tell it
to play (presuming such a chip exists).  The point is that something
may say it "does MIDI" and be technically true, but it may not do
everything you expect.

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-----
http://mindspring.com/~benbradley

Re: MIDI Decoder Chip?
On Thu, 16 Jun 2005 17:11:50 GMT, Ben Bradley

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I am not sure. It has been years since I have read any of the
datasheets, or looked at these devices. There were a few fairly
complex devices available since the CPUs used as the main CPU
were not that fast.

Regards
  Anton Erasmus



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