USBMIDI

Table of Contents

  1. Hello World
  2. API
  3. More example
  4. Related

The USBMIDI interface can be used to send and receive MIDI messages over USB using the standard USB-MIDI protocol.

Using this library, you can do things like send MIDI messages to a computer (such as to record in a sequencer, or trigger a software synthesiser) and receive messages from a computer (such as actuate things based on MIDI events)

The USB connector should be attached to

  • p31 (D+), p32 (D-) and GND for the LPC1768 and the LPC11U24
  • The on-board USB connector of the FRDM-KL25Z

Hello World

» Import this program
USBMIDI_HelloWorld - main.cpp

// Hello World example for the USBMIDI library

#include "mbed.h"
#include "USBMIDI.h"

USBMIDI midi;

int main() {             
    while (1) {    
        for(int i=48; i<83; i++) {     // send some messages!
            midi.write(MIDIMessage::NoteOn(i));
            wait(0.25);
            midi.write(MIDIMessage::NoteOff(i));
            wait(0.5);
        }
    }
}

API

» Import this library into a program
USBDevice - USBMIDI Class Reference

Public Member Functions

  USBMIDI (uint16_t vendor_id=0x0700, uint16_t product_id=0x0101, uint16_t product_release=0x0001)
  Constructor.
void  write ( MIDIMessage m)
  Send a MIDIMessage .
void  attach (void(*fptr)( MIDIMessage ))
  Attach a callback for when a MIDIEvent is received.

More example

In this example, you can control the MIDI message sent with buttons

» Import this program
USBMIDI_Receive - main.cpp

// Hello World example for the USBMIDI library

#include "mbed.h"
#include "USBMIDI.h"

//USBMIDI object
USBMIDI midi;


// Leds which will be switch on or off according to a MIDImessage
BusOut leds(LED1, LED2, LED3, LED4);

BusInOut buttons(p22, p23, p24, p25);

void show_message(MIDIMessage msg) {
    switch (msg.type()) {
        case MIDIMessage::NoteOnType:
            switch (msg.key()) {
                case 48:
                    leds = (1 << 0);
                    break;
                case 49:
                    leds = (1 << 1);
                    break;
                case 50:
                    leds = (1 << 2);
                    break;
                case 51:
                    leds = (1 << 3);
                    break;
            }
            break;
        case MIDIMessage::NoteOffType:
        default:
            leds = 0;
    }
}

int main() {
    uint8_t bus = 0;
    uint8_t p_bus = 0;

    // call back for messages received
    midi.attach(show_message);

    while (1) {

        //if buttons state changes, send a MIDI message
        bus = buttons.read();
        for (int i = 0; i < 4; i++) {
            if ( (bus & (1 << i)) != (p_bus & (1 << i))) {
                if (bus & (1 << i)) {
                    midi.write(MIDIMessage::NoteOn(48 + i));
                } else if ( !(bus & (1 << i)) ) {
                    midi.write(MIDIMessage::NoteOff(48 + i));
                }

            }
        }
        wait(0.001);
        p_bus = bus;
    }
}


Ask a question
Last modified 01 Mar 2013, by user Samuel Mokrani. 1 reply

1 related question:

1
answers
. user Manipura Chakra
2 months ago

 

1 comment:

user t b
21 Nov 2011

This looks really cool. I notice USBDevice is setup with classes for mouse, keyboard, serial, and MIDI. Is it possible to have a USB MIDI device and a USB Serial device (and maybe a mouse and keyboard :)) all appear as devices, all at the same time? That would be a really powerful capability.

Terry

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