AppleMIDI (aka rtpMIDI) for Arduino

Enables an Arduino with IP/UDP capabilities (Ethernet shield, ESP8266, ESP32, ...) to participate in an AppleMIDI session.

Features

• Build on top of the popular FortySevenEffects MIDI library
• Tested with AppleMIDI on Mac OS (Tahoe) and using rtpMIDI from Tobias Erichsen on Windows 10 & 11.
• Send and receive all MIDI messages
• Uses callbacks to receive MIDI commands (no need for polling)
• Automatic instantiation of AppleMIDI object (see at the end of 'AppleMIDI.h')
• Compiles on Arduino, MacOS (XCode) and Windows (MSVS)

New in 3.5.0

• Safer session and RTP parsing (known-SSRC MIDI only, UDP datagram isolation, wrap-safe sequence numbers)
• RTP is sent only after the data-port handshake; invitation reject matches by initiator token
• Size gates: APPLEMIDI_SMALL, ONE_PARTICIPANT, NO_SESSION_NAME (see Memory footprint)
• Large SysEx is split per RFC 6295 (F0/F7); see SysEx and extra F0/F7 bytes

Installation

Clone locally or download from the Arduino IDE Library Manager, search for AppleMIDI

This will also install FortySevenEffects MIDI library

Basic Usage

#include <Ethernet.h>
#include <AppleMIDI.h>

byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };

APPLEMIDI_CREATE_DEFAULTSESSION_INSTANCE(); 

void setup()
{
  Ethernet.begin(mac);

  MIDI.begin(); // listens on channel 1
}

void loop()
{
  // Listen to incoming notes
  MIDI.read();
  
  ....
  if (something) {
    // Send MIDI note 40 on, velocity 55 on channel 1
    MIDI.sendNoteOn(40, 55, 1);
  }
}

More usages in the examples folder and in the wiki

Hardware

• Arduino/Genuino (Mega, Uno, Arduino Ethernet, MKRZERO, ...)
• ESP8266 (Adafruit HUZZAH ESP8266, Sparkfun ESP8266 Thing Dev)
• ESP32 (Adafruit HUZZAH32 – ESP32 Feather Board) Wi-Fi
• ESP32 with W5500 Setup
• ESP32 ETH W5500 (Native ESP32 W5500 support)
• Seeed Studio XIAO ESP32 C3
• Teensy 3.2 & 4.1
• Adafruit Feather M0 WiFi - ATSAMD21 + ATWINC1500

Network Shields

• Arduino Ethernet shield (Wiznet W5100 and W5500)
• Arduino Wifi R3 shield
• MKR ETH shield (W5500 and W6100 based)
• Teensy WIZ820io W5200
• Teensy 4.1 with Ethernet Kit
• ESP32 with W5500

Notes

SysEx and extra F0/F7 bytes

Outgoing SysEx that does not fit in MaxMidiOutSize (default 64) is split across RTP packets per RFC 6295: the current packet ends with F0 and the next starts with F7. USB, serial, and BLE do not add those markers, so a capture can look malformed (#169). AppleMIDI/rtpMIDI receivers reassemble them. Raise MaxMidiOutSize (and usually MaxBufferSize) in a custom Settings struct if you need a larger SysEx in one command section.

Session names

Session names can get really long on Macs (eg 'Macbook Pro of Johann Gambolputty .. von Hautkopft of Ulm') and will be truncated to MaxSessionNameLen.

Memory footprint

Define these in the sketch before #include <AppleMIDI.h>:

• ONE_PARTICIPANT — one remote peer (saves a participant slot)
• NO_SESSION_NAME — do not store session names (~100 bytes)
• APPLEMIDI_SMALL — skip unused journal parsing and outbound RS
  (APPLEMIDI_PARSE_JOURNALS / APPLEMIDI_KEEP_RECEIVER_FEEDBACK keep those while still using APPLEMIDI_SMALL)

APPLEMIDI_SMALL is used in examples/AVR_MinMemUsage. More on the wiki.

Ethernet buffer size

It's highly recommended to modify the Ethernet library - learn more

Latency

Use wired Ethernet to reduce latency, Wi-Fi increases latency and latency varies. More of the wiki

Arduino IDE (arduino.cc)

• 1.8.16
• 2.3.10

Contributing

I would love to include your enhancements or bug fixes! In lieu of a formal styleguide, please take care to maintain the existing coding style. Please test your code before sending a pull request. It would be very helpful if you include a detailed explanation of your changes in the pull request.