Nano not receiving MIDI messages

Using Arduino Audio
1

Hi, so I am currently creating a MIDI to CV module and am still having trouble with my MIDI input circuit. I am following this circuit as my guideline and am sending MIDI messages via MIDI interface with the use of this cable. I am also using this software called MIDIKeys as a virtual keyboard for the MIDI notes. Unfortunately, every time I play a note on the keyboard the Arduino doesn't respond with the blink of the LED. I could really use some guidance on fixing this problem.

Below is also the code that I'm using:

#include <MIDI.h>  // Add Midi Library

#define LED 13    // Arduino Board LED is on Pin 13

//Create an instance of the library with default name, serial port and settings
//MIDI_CREATE_DEFAULT_INSTANCE();
MIDI_CREATE_DEFAULT_INSTANCE();

void setup() {
  pinMode (LED, OUTPUT); // Set Arduino board pin 13 to output
  MIDI.begin(MIDI_CHANNEL_OMNI); // Initialize the Midi Library.
  MIDI.turnThruOff();
  MIDI.setHandleNoteOn(MyHandleNoteOn); 
  MIDI.setHandleNoteOff(MyHandleNoteOff); 
  Serial.begin(31250);
}

void loop() { // Main loop
  MIDI.read(); // Continuously check if Midi data has been received.
}

void MyHandleNoteOn(byte channel, byte pitch, byte velocity) { 
  digitalWrite(LED,HIGH);  //Turn LED on
}

void MyHandleNoteOff(byte channel, byte pitch, byte velocity) { 
  digitalWrite(LED,LOW);  //Turn LED off
}
2

how can you check if it reverse polarity or a signal at all comes on optocoupler?

3

I don't know about the cable, i tend to start out with something that i know can transmit (like a midi keyboard) or know for sure can receive (like my soundcard with 1x1 midi port)

MIDI_CREATE_DEFAULT_INSTANCE();

so this means you should connect to hwSerial, on the nano that is pins 0 & 1.

Serial.begin(31250);

there is no need for this, it is included in

MIDI.begin(MIDI_CHANNEL_OMNI);

the problem with this is

  MIDI.setHandleNoteOn(MyHandleNoteOn); 
  MIDI.setHandleNoteOff(MyHandleNoteOff);

that in many cases, a 'notyeOff' commands is transmitted as a 'noteOn' with velocity '0'
It can't be the issue here (yet) since that would mean that the LED would be continually 'on' , but keep it in mind.

well it is 'safe' to swap the pins on the input side of the opto-coupler and check the result.
Which is pin 4 and which is pin 5 on a din plug can be a bit of guess work, are you looking at the plug from the front or the rear and is it male or female etc...
You can test the polarity with a simple test 'snippet'

pinMode(RX_PIN, INPUT);
delay(500);
while (digitalRead(RX_PIN);
digitalWrite(LED,HIGH);

should do the trick, if the pin goes LOW when you send something, the LED should come on.

4

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