MIDI8d – 8 Digital Outputs


MIDI8d is a simple yet powerful 8 Digital Outputs from a MIDI TRS input connection.

Arduino Nano
The core of the MIDI8d is the classic Arduino Nano.

Different firmwares (Arduino sketches) can be uploaded, to adapt or completely change the behavior.

Typical uses are:

  • 8 Drums outputs, reacting to MIDI Channel 10 (notes 36 to 43)
  • MIDI Clock ticks, with various time divisions and Start/Stop Gate outputs

MIDI input

The MIDI input jack is a Stereo (TRS type A) connector.

The Tip corresponds to the Sink signal, the Ring is connected to the Source.

The MIDI input circuit is pretty simple and the main component is the high speed Optocoupler 6N137 (U1). The output is pulled-up by R5 and is active low.


Open source firmwares can be found here: https://github.com/dhaillant/midi8d/

Several examples are provided (8 gates from MIDI channel 10, MIDI channel activity monitor, MIDI clock breakout, etc).


For a detailed BOM, please have a look at the Interactive BOM web page below in “Downloads & documentation” section.

If you choose a PCB set with pre-assembled SMD stuff, you have some Through Hole components to solder yourself:

Quantity Description Link
9 3mm LEDs (yellow, 2mA, typ. KingBright L-934LYD)
8 mono jack sockets Thonk
1 stereo jack socket Thonk
4 4-pin female sockets (2.54mm pin pitch)
4 4-pin male pin arrays (2.54mm pin pitch)
1 6N137 DIP optocoupler
1 8 pin DIP/DIL socket
1 5 x 2 pin array for Eurorack power connector
1 1N4007 or 1N5819 diode
1 10µF electrolytic capacitor (25V minimum) Mouser
1 Arduino Nano
2 15-pin female sockets (2.54mm pin pitch)

Downloads & documentation


3 thoughts on “MIDI8d – 8 Digital Outputs

  1. Hi David,

    Just been looking at the MIDI Clock code with the view to buying the PCB / Panel soon.

    Quickly tried compiling the code from the github site and it failed, error on Line 73:

    pinMode(MIDI_LED, OUTPUT);

    Think this definition should be:

    pinMode(MIDI_LED_PIN, OUTPUT);

    Compiled ok with that change.

    Will be it touch soon,



    p.s. the MiniSynth built a while back is working fine

    1. Hello Bob,
      Thank you very much for pointing this out!
      Indeed I made a typo here. The Github version is now updated with the correct pin definition.

      1. Hi David,
        Thanks for the unexpected ‘extra’. Built both modules and all working fine.
        Need to re-arrange the rack and expand it to give them a permanent home.

Leave a Reply

Your email address will not be published. Required fields are marked *