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MIDI Decoder Chip?

Discussion in 'Electronic Components' started by [email protected], Jun 13, 2005.

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  1. Guest

    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
     
  2. jim dorey

    jim dorey Guest

    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.
     
  3. Neil Bradley

    Neil Bradley Guest

    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
     
  4. Dr Justice

    Dr Justice Guest

    Yes, It's called an UART.
    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
    --
     
  5. 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.
     
  6. Guest

    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
     
  7. Guest

  8. Tim Mitchell

    Tim Mitchell Guest

    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.
     
  9. Rolf Blom

    Rolf Blom Guest

    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
     
  10. 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.
     
  11. 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
     
  12. Ben Bradley

    Ben Bradley Guest

    In comp.arch.embedded,sci.electronics.components, On Thu, 16 Jun 2005
    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.
     
  13. 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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