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Thread: MIDI Out as also MIDI Thru?

  1. #1
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    MIDI Out as also MIDI Thru?

    Hi I'm following the circuit here: https://www.pjrc.com/teensy/td_libs_MIDI.html for Teensy 3.x. Many MIDI controllers and synths today use the MIDI Out port as the MIDI thru. I am trying the achieve the same thing. Using this circuit for the Teensy is it as simple as connecting the received signal from pin 6 on the 6N138 to Pin 5 on the MIDI Out DIN?

  2. #2
    Senior Member oddson's Avatar
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    I think you need to add some buffer (e.g. feed both sides of an AND gate or back-to-back NOT gates).
    Click image for larger version. 

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    A merge out should be feasible but I don't do serial MIDI much and can't recall how easy it really is.

  3. #3
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    The way "thru" works in such devices is using software I think, since the use of the output port has to be shared
    between local output packets and "thru" packets without mangling either. I think its common to be able to
    reconfigure MIDI channels for the "thru" packets too in such a setup so as to be able to prevent channel clashes.

    You can't get away with simply combining two MIDI streams at a low level, garbled packets will be very bad news,
    leaving notes stuck on and all sorts of mayhem.

  4. #4
    Senior Member oddson's Avatar
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    Yes, merge must be done in software but 'thru' ports can just buffer the input signal. It's to allow a master controller daisy chain sound moduals.

    I was responding to the idea you could drive the port without a buffer but I didn't notice they mean to have a 'merge' output not a 'thru.'

  5. #5
    Senior Member ETMoody3's Avatar
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    The MIDI library does a THRU from input to the output by default. You have to shut it off if not needed, or attach the function to a switch or soft control.

  6. #6
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    Quote Originally Posted by ETMoody3 View Post
    The MIDI library does a THRU from input to the output by default. You have to shut it off if not needed, or attach the function to a switch or soft control.
    Oh wow I did not know this. Thanks for this info! Is there anywhere this explains this in more detail? I may want to have the option to disable this feature if it causes issues.

  7. #7
    Senior Member ETMoody3's Avatar
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    https://fortyseveneffects.github.io/...ry/a00039.html

    Here's the documentation.

    Read the whole thing...you'll thank yourself later.

  8. #8
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    Quote Originally Posted by ETMoody3 View Post
    https://fortyseveneffects.github.io/...ry/a00039.html

    Here's the documentation.

    Read the whole thing...you'll thank yourself later.
    Awesome thanks!

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