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Thread: Teensy 4.1 MIDI iN using 6N138 5V or 3.3V

  1. #1

    Teensy 4.1 MIDI iN using 6N138 5V or 3.3V

    Does the IC work with 3.3V or does it need 5V? If 5V, is the output compatible with Rx0 Pin?

  2. #2
    Senior Member ETMoody3's Avatar
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    As far as I know No, the 6N138 does not work at 3.3 v.

    Look at the Adafruit midi feather wing which operates directly with 3.3v logic or consider a suitable logic level shifter like TXS0108E

    https://www.adafruit.com/product/4740

    Alternative is to use this schematic which powers the 6N138 at 5 v but pulls the output logic to a safe 3.3v.

    Click image for larger version. 

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    Last edited by ETMoody3; 07-11-2021 at 02:39 AM.

  3. #3
    Senior Member PaulStoffregen's Avatar
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    6N138 does indeed require 5V power.

    But it can give a 3.3V output signal while running on 5V power. Its output is open collector, so just connect the 470 ohm pullup resistor to 3.3V. See the schematic on this page for details:

    https://www.pjrc.com/teensy/td_libs_MIDI.html

  4. #4
    Thanks. So my design should work?
    Click image for larger version. 

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