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 Max/MSP). Thus, note the difference between the previous midi2Max() 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 );
  }