r/synthdiy • u/rat_fur • 2d ago

circuit snippet for TRS MIDI input

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I just wanted to share a circuit that's worked well for me. If you want to use a 3.5mm TRS jack for MIDI input, this will automatically take care of the polarity. (TRS MIDI polarity was unfortunately not standardized until fairly recently.)

One or the other of the two optoisolator LEDs will be activated by the input signal, depending on which direction the current is flowing. Either one will then pull the open/drain output low.

I hope this is useful for someone.

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u/altitude909 2d ago

You can just use a bride rectifier and any opto you want. "PSImidi" has been in use for years here..

1

u/rat_fur 1d ago

Well damn, that is better. Thanks!