MIDI Output from the Arduino using 5-Pin MIDI Connector

A schematic of a MIDI (IN and OUT) interface (from http://www.borg.com/~jglatt/).

• A “true” MIDI stream is a series of bytes sent out in sequence, without spaces or line breaks (which were used in the above examples only to facilitate parsing of bytes in Pd). Thus, note the difference between the previous midi2Pd() function and the midiSend() function below.

• The serial (MIDI) data is sent out the transmit pin of the Arduino (though you need a MIDI connector and a MIDI device to send it to).

• From the schematic above, we need to connect a 220 ohm resistor between +5V and pin 4 of the MIDI connector and another 220 ohm resistor between pin 5 of the MIDI connector and the transmit pin (1) of the Arduino board.

• Note that the serial transmission rate below is set to the MIDI serial rate of 31250 bits per second.

  #define MIDI_ON 144
  #define MIDI_OFF 128
  #define MIDI_CHANNEL 0
  
  char status = 0;
  
  void setup()
  {
    Serial.begin( 31250 );       // set the MIDI baud rate
  }
  
  void loop()
  {
    status = MIDI_ON + MIDI_CHANNEL;
    midiSend( status, 60, 64 );   // send a MIDI ``note on'' message
  
    delay( 500 );                 // delay 500 milliseconds
  
    status = MIDI_OFF + MIDI_CHANNEL;
    midiSend( status, 60, 0 );   // send a MIDI ``note off'' message
  
    delay( 500 );                 // delay 500 milliseconds
  }
  
  // Send a 3 byte MIDI message (without checking values)
  void midiSend( char cmd, char data1, char data2 )
  {
    Serial.write( cmd );
    Serial.write( data1 );
    Serial.write( data2 );
  }