MIDI - support for virtual wires/jacks

[kaysievers]

Here is a working proof-of-concept to support virtual wires/jacks for MIDI devices:
https://github.com/kaysievers/Adafruit_TinyUSB_Arduino/tree/midi-jacks
https://github.com/kaysievers/ArduinoCore-samd/tree/tinyusb-midi-jacks

Tested to create 1 or 3 virtual jacks.

Please let me know how to proceed, or if you have any better ideas. I would finish it properly if this is an interesting feature. Thanks!

[kaysievers]

Both repositories are updated. The USB side appears to work correctly. The raw device has the identical descriptors with the old and new code, when only one wire/jack is used. I can send messages to all ports and receive them, but I can't distinguish them inside the MIDI device.

To make use of the wire/jack data, tinyusb MIDI needs to be extended/changed. If I read the code correctly, the current tinyusb MIDI device code throws away the first byte of the USB packet and the information about the cable/jack number gets lost:

cores/arduino/Adafruit_TinyUSB_Core/tinyusb/src/class/midi/midi_device.c
tu_fifo_write_n(&midi->rx_ff, &buffer[i + 1], count);

The FortySevenEffects MIDI library uses the streaming format because its focus is the legacy serial line MIDI format. The Arduino MIDIUSB library always had the full USB packet to read.

The future/upcoming MIDI2.0 protocol is a pure packet-based transport, there is no streaming support at all, and it will not work over legacy serial lines. It would be nice to have a raw interface to the packets instead of stuffing it into the old serial line format.

@hathach any ideas what's the best way forward here? Can we change the tinyusb MIDI buffering to store all 4 bytes in the FIFO and move the packing of the legacy streaming format to the read() method?

[hathach]

@kaysievers thank you, this is a great addition to add. I am totally OK to change to writing full 4 bytes format and move away from streaming format as well. In fact, I am open to alter all the usb stack with a good reason. Though I am not too familiar with MIDI usage, do you happen to know an library to conveniently replace FortySevenEffects when we switch to the packet format.

What I need is only an proof-of-concept example to work upon, would you mind adding a new midi example based on this https://github.com/adafruit/Adafruit_TinyUSB_Arduino/blob/master/examples/MIDI/midi_test/midi_test.ino which

• Has 2 virtual pair (in & out) of ports ( more is better but 2 is convincing enough)
• Each output port has an distinguish note sequence so that we could notice the difference when attaching speaker to chanel0, chanel1
• If possible: library to replace FortySevenEffects to parse incoming event for each chanel.

Make all changes that you think is needed, then submit your PR on both 2 repos. I will review, merge, and will refactor if needed. Also tested to make sure it works on other platform such as nrf5x and its bare metal C example in my core repo as well. Let's me know if you need an more detail or clarification on the usb stack.

Notice: don't use C++ static_cast with file inside Adafruit_TinyUSB_Core/tinyusb/src, those are intended to compile with both C and C++.

[kaysievers]

do you happen to know an library to conveniently replace FortySevenEffects when we switch to the packet format

For my own use, I have a tiny wrapper around MIDIUSB in my devices. I would be totally fine to just port that to a new Adafruit_USBD_MIDI device packet interface and not use any another library.

The code to convert from packets to a stream and the stream class interface for the FortySevenEffects lib is probably still the easiest way for people to build devices. At least as long as there are no need to support MIDI2.0 protocol devices.

If we add a new packet interface, would you like to keep the stream conversion code in the tinyusb core code or move it to the Adafruit_USBD_MIDI code?

[kaysievers]

Here is a packet interface for tinyusb, the streaming methods do the packet mangling now, the FIFO stores the original packets:
https://github.com/kaysievers/ArduinoCore-samd/tree/tinyusb-midi-packets

Here is the Adafruit_TinyUSB part:
https://github.com/kaysievers/Adafruit_TinyUSB_Arduino/tree/midi-packet-interface

[kaysievers]

With all the 4 branches applied:
https://github.com/kaysievers/Adafruit_TinyUSB_Arduino/tree/midi-jacks
https://github.com/kaysievers/ArduinoCore-samd/tree/tinyusb-midi-jacks
https://github.com/kaysievers/ArduinoCore-samd/tree/tinyusb-midi-packets
https://github.com/kaysievers/Adafruit_TinyUSB_Arduino/tree/midi-packet-interface

Three virtual ports are requested:

  Adafruit_USBD_MIDI V2MIDI(3);

No further MIDI library is used, it just sends the raw USB packet to the Adafruit_USBD_MIDI device on the virtual port 1:

        uint8_t msg[] = {
          0x10 | MIDI_STATUS_NOTE_ON,
          (uint8_t)((MIDI_STATUS_NOTE_ON << 4) | 0),
          (uint8_t)MIDI_PERCUSSION_ACOUSTIC_SNARE,
          (uint8_t)FSR.note_velocity
        };

        V2MIDI.send(msg, 4);

And two USB packets received note-on ,note-off and the first byte correctly shows virtual port 2:

2-9 144 71 78
2-8 128 71 64

The OS and the music application recognizes the 3 separate ports of the device properly:

@hathach, it would be nice if you can have a look over the code, if it looks fine I can submit the PRs.

[kaysievers]

Here is an example sketch that uses the virtual ports:

Every port continuously sends out notes:
Port #1, channel 6: monochord (single tone)
port #2, channel 9: dichord (two tones)
port #3, channel 12: trichord (three tones)

Notes received on the ports let the built-in LED blink one, two,
or three times.

https://github.com/kaysievers/Adafruit_TinyUSB_Arduino/tree/midi-jacks-example

Tested on ItsyBitsy M0.

[hathach]

@kaysievers sorry, I have been busy with other thing lately, will test this out soon enough :)

[kaysievers]

Here is the first pull request, which is the preparation for the virtual wire code. It should not change any behavior.

adafruit/ArduinoCore-samd#179

[kaysievers]

Here is the counterpart which adds an interface to request more than one MIDI port/wire.

#31

[hathach]

@kaysievers thank you very much for your contribution for the issue and PR. Though I am currently in the middle of other works. I will try to review and work on this as soon as I could.

[kaysievers]

@hathach thanks for merging all the PRs.

Just a short update. I have rebased everything, these are the remaining changes now:
https://github.com/kaysievers/ArduinoCore-samd/tree/tinyusb-midi-packets
https://github.com/kaysievers/Adafruit_TinyUSB_Arduino/tree/midi-packet-interface

I've merged the example sketch into midi-packet-interface. It all seems to work fine

The tinyusb-midi-packets change still needs some cleanup work. I'll do this this week, and submit both as PRs. Thanks!

[hathach]

@kaysievers I should be the one to say thanks for your work, and your patient. I should have done this earlier :) .