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Midi Out Isolation Chip — Parallax Forums

Midi Out Isolation Chip

Rick_HRick_H Posts: 116
edited 2010-10-30 10:48 in Propeller 1
is a darlington or an opto better for the prop to Midi out? 3.3V to 5V I don't think using the darlinggton is bad but is the opto a better solution? The MIDI spec shows 2 inverting buffers. Anyone have a standard they use for the prop to MIDI out?

Comments

  • Bob Lawrence (VE1RLL)Bob Lawrence (VE1RLL) Posts: 1,720
    edited 2010-10-26 09:18
    Re: Isolation Chip

    Are you talking about input or output.

    For output you can have a look at the schematic in this post:
    http://forums.parallax.com/showthread.php?t=118144&highlight=midi



    For input you could use

    4N28 optocoupler = NTE3093 Optoisolator or a use a TOSHIBA Photocoupler:

    http://www.semicon.toshiba.co.jp/docs/datasheet/en/Opto/TLP552_en_datasheet_090217.pdf
  • Rick_HRick_H Posts: 116
    edited 2010-10-30 01:22
    Ahh so jut dropping the current limiting resistor to 100 I can use 3.3v. Not exactly midi specification but I may try that. Wurlitzers code is handy also, was just strting to write mine but why reinvent the wheel.
  • 65816581 Posts: 132
    edited 2010-10-30 03:43
    I'm getting good and reliable results with a 6N138 for input
    and a 74HC14 for output. You can also use 2 resistors for the output -
    but if you want to be on the safe side, I'd recommend the hex inverting
    schmitt trigger (74HC14).
  • Rick_HRick_H Posts: 116
    edited 2010-10-30 10:48
    I have a bunch of darlingtons laying around, I may just give them a try with 5V. I really don't want to deviate from the midi specs too much. If that don't work I'll defiantly use the 74HC14. using the 5V will get me closer to the spec.
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