Go Down

Topic: MIDI out messages doesn't work with external power supply  (Read 700 times) previous topic - next topic


Trying to build an Arduino MIDI controller that only sends data, I use the attached test code which suppose to send a NoteOn and then NoteOff MIDI massage repeatably via Tx pin.
It works just fine when the Arduino is connected to the computer through the USB port, but when I try to use a power supply of 12V, 1.5A everything on the board looks fine, but MIDI massages being sent continuously and contains random staff.
I use MIDI OX to read the MIDI that comes from the Arduino so I can see what I got according to what I expect.

Attached is a photo of what I get in MIDI-OX when the Arduino is powered with external supply.

Thanks a lot

the test code:
Code: [Select]
#include <MIDI.h>

#define LED 13


void setup()
  pinMode(LED, OUTPUT);

void loop()
  digitalWrite(LED, HIGH);
  MIDI.sendNoteOn(60, 127, 1);
  MIDI.sendNoteOff(60, 0, 1);
  digitalWrite(LED, LOW);


How is it wired up?
This sort of problem normally happens because the ground is not connected.
What sort of Arduino do you have?
How are you connecting it to your midi device?


Im using  Arduino Uno

Its a little bit hard to understand from the pics, but the wiring is:
External supply to the Arduino built in jack, and then the exact same wiring as here:

then I use this cheap MIDI to USB cable you can see in the close up picture. I just opened the case for some modification. and in the close up picture the black wire is MIDI V+ and the red wire is the MIDI tx.

I tried to ground the rx pin of the Arduino without success



I am a bit puzzled by those photos. It seems you have connected the MIDI out from the USB lead to a MIDI out interface on the Arduino.


Hi, i have the same problem.

Tx is sending messages but midi-usb don't.

It's Working fine when the board is plugged to usb, the problem is with power supply.

Did u find out what's the cause?

Go Up