Multiple MIDI in ports with libpd

jeppius

Hi,
what is the current state of development in MIDI support through Bela's libpd? I would need to respond to two usb midi devices, a keyboard for notes and a controller for cc's. Would that be feasible?

giuliomoro

That's an interesting question, I thought through it last week but I have had no way to test it yet.

The wiki page on libpd MIDI support states that

Channel numbers in libpd encode both Pd channels and ports in the following way: libpd_channel = pd_channel + 16 * pd_port. In particular, any nonnegative integer is a valid channel number as far as libpd is concerned.

So having multiple interfaces should just be a matter of adding 16 to the channel number for each interface above the first one, so having:
interface 0, channels 0-15
interface 1, channels 16-31
* interface 2, channels 32-47
and so on.

The first step would require to declare an array of Midi objects, e.g.: Midi midi[2] instead of the current Midi midi and set each of them to read from the appropriate port.

Then, you'd have to edit the callbacks so that they support multiple ports.
For outputs, you should e.g.:
edit

void Bela_MidiOutNoteOn(int channel, int pitch, int velocity) {
    rt_printf("noteon: %d %d %d\n", channel, pitch, velocity);
    midi.writeNoteOn(channel, pitch, velocity);
}

to something like

void Bela_MidiOutNoteOn(int channel, int pitch, int velocity) {
    int port = 0;
    while(channel > 16){
       channel -= 16;
       port += 1;
    }
    rt_printf("noteon: %d %d %d %d\n", port, channel, pitch, velocity);
    midi[port].writeNoteOn(channel, pitch, velocity);
}

for inputs, which is what you are actually interested in, you should iterate through the available MIDI ports, e.g.: replace

    while((num = midi.getParser()->numAvailableMessages()) > 0){
        static MidiChannelMessage message;
        message = midi.getParser()->getNextChannelMessage();
        //message.prettyPrint(); // use this to print beautified message (channel, data bytes)
        switch(message.getType()){
            case kmmNoteOn:
            {
                int noteNumber = message.getDataByte(0);
                int velocity = message.getDataByte(1);
                int channel = message.getChannel();
                libpd_noteon(channel, noteNumber, velocity);
                break;
            }

with something like

for(unsigned int port = 0 ; port < numMidiPorts; ++port){
    while((num = midi[port].getParser()->numAvailableMessages()) > 0){
        static MidiChannelMessage message;
        message = midi[port].getParser()->getNextChannelMessage();
        switch(message.getType()){
            case kmmNoteOn:
            {
                int noteNumber = message.getDataByte(0);
                int velocity = message.getDataByte(1);
                int channel = message.getChannel();
                libpd_noteon(channel + port * 16, noteNumber, velocity);
                break;
            }
 ....

I can give it a try later today, but then you'll have to test it yourself as I currently have no way of connecting multiple MIDI devices to my Bela.

jeppius

Cool, sounds perfectly feasible, whenever you incorporate such functionality I would try it and let you know.

giuliomoro

can you send me the outputs returned by these commands on your Bela while the midi devices are connected?

ls /dev/midi*

find /dev/snd

amidi -l

jeppius

Sure, with device A:
root@bela ~$ ls /dev/midi*
/dev/midi1
root@bela ~$ find /dev/snd
/dev/snd
/dev/snd/by-path
/dev/snd/by-path/platform-musb-hdrc.1.auto-usb-0:1:1.0
/dev/snd/by-id
/dev/snd/by-id/usb-KORG_INC._nanoKONTROL2-00
/dev/snd/controlC1
/dev/snd/midiC1D0
/dev/snd/seq
/dev/snd/timer
root@bela ~$ amidi -l
Dir Device Name
IO hw:1,0,0 nanoKONTROL2 MIDI 1

with device A and device B:

root@bela ~$ ls /dev/midi*
/dev/midi /dev/midi1
root@bela ~$ find /dev/snd
/dev/snd
/dev/snd/controlC0
/dev/snd/midiC0D0
/dev/snd/by-path
/dev/snd/by-path/platform-musb-hdrc.1.auto-usb-0:1.2:1.0
/dev/snd/by-path/platform-musb-hdrc.1.auto-usb-0:1.3:1.0
/dev/snd/by-id
/dev/snd/by-id/usb-1a86_USB2.0-MIDI-00
/dev/snd/by-id/usb-KORG_INC._nanoKONTROL2-00
/dev/snd/controlC1
/dev/snd/midiC1D0
/dev/snd/seq
/dev/snd/timer
root@bela ~$ amidi -l
Dir Device Name
IO hw:0,0,0 USB2.0-MIDI MIDI 1
O hw:0,0,1 USB2.0-MIDI MIDI 2
IO hw:1,0,0 nanoKONTROL2 MIDI 1

giuliomoro

Nice, so you can find the updated code in the dev-midi branch.
To use an experimental branch on your board, check out the instructions here.

You will then have to manually edit the core/default_libpd_render.cpp file and add your devices to it. See here how to edit the core code.

In default_libpd_render.cpp, scroll down to setup()and add your devices similarly to those that are already there

     gMidiPortNames.push_back("hw:1,0,0");

In your case you will need the following:

     gMidiPortNames.push_back("hw:0,0,0");
     gMidiPortNames.push_back("hw:0,0,1");
     gMidiPortNames.push_back("hw:1,0,0");

It may well be that only one of "hw:0,0,1" "hw:0,0,0" will be inactive. Once you find out you can take it out.

giuliomoro

This may help later on when trying to get consistent behaviour in the order the cards show up http://alsa.opensrc.org/MultipleCards .

giuliomoro

Ok so now I've improved it even more, not much is going to change for you, but lots has changed in the background, so it requires thorough testing.
I tested with 2 cards (one of which with two subdevices), but only one card of could respond to output, so testers welcome!

Also, it is up for debate whether it makes sense to reduce the need for a custom render.cpp by providing a [r bela_config] object that responds to some configuration messages ( e.g.: how many/which MIDI ports).

jeppius

Well I am open to test multiple midi devices...not really multiple sound cards. What steps should I follow?

giuliomoro

Testing procedure is the same as above.

You said above you have two USB midi devices, they will be two different cards, but ALSA may recognize multiple subdevices for each card.
To find out all the subdevices available on your machine, you use amidi -l.
In your case, that shows:

root@bela ~$ amidi -l
Dir Device Name
IO hw:0,0,0 USB2.0-MIDI MIDI 1
O hw:0,0,1 USB2.0-MIDI MIDI 2
IO hw:1,0,0 nanoKONTROL2 MIDI 1

which means you have two cards (hw:0, hw:1) and the first one has two subdevices (hw:0,0,0, hw:0,0,1), so those are the device names you should add to default_libpd_render.cpp as explained above.
You are probably going to receive an error when trying to open hw:0,0,1 for reading (as it is an output ( O) only device), but it should still work.

jeppius

ok, but should I update the Bela?

giuliomoro

Yes, instructions on how to do so should be in my post above

jeppius

ups...perfectly doccumented, but I already plan to give a brief performance this friday and "editing the core" seems a bit adventurous...I will let you know as soon as I can anyway.

giuliomoro

well you only have to edit that file to add your ports to it.

This is the "safer" commit, where there is easy support for multiple interfaces, but not major overhaul of the core code, so you could safely update your board to this.

https://github.com/BelaPlatform/Bela/tree/5e067bb538d5a36b7a2b392a8e352bcc0ac02479

jeppius

I just had some time to make the required changes and test it, however I run into problems when trying to have my MIDI devices opened. What should be the proper procedure when plugging MIDI devices? Most times they just don’t appear, I am not yet sure whether they must be plugged at boot time, once booted, after a first reboot, with the IDE shutdown, the card reset… I tried many combinations and still am I not sure which is the right one.

jeppius

Besides, once properly recognized I do get MIDI data from them, but the console shows and enourmous amount of read/write errors. My patch only has a [notein] and [ctlin] object so, not sure what's going on...

devices:

root@bela ~$ amidi -l
Dir Device Name
IO hw:0,0,0 USB2.0-MIDI MIDI 1
O hw:0,0,1 USB2.0-MIDI MIDI 2
IO hw:1,0,0 nanoKONTROL2 MIDI 1
root@bela ~$

console:

On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 92,
CTL: 92 0 33
Error while reading midi 9
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 93,
CTL: 93 0 33
Error while reading midi 9
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 94,
CTL: 94 0 33
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 95,
CTL: 95 0 33
Error while reading midi 9
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 96,
CTL: 96 0 33
Error while reading midi 9
Error occurred while writing: 1079283616
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 97,
CTL: 97 0 33
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 98,
CTL: 98 0 33
Error while reading midi 9
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 99,
CTL: 99 0 33
Error while reading midi 9
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 100,
CTL: 100 0 33
Error while reading midi 9
Error occurred while writing: 1079283616
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 101,
CTL: 101 0 33
Error while reading midi 9
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 102,
CTL: 102 0 33
Error while reading midi 9
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 103,
CTL: 103 0 33
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 104,
CTL: 104 0 33
Error while reading midi 9
Error while reading midi 9
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 105,
CTL: 105 0 33
Error occurred while writing: 1079283616
Error while reading midi 9
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 106,
CTL: 106 0 33
Error while reading midi 9
Error while reading midi 9
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 107,
CTL: 107 0 33
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
On port 2 (hw:1,0,0): type: control change, channel: 0, data1: 0, data2: 108,
CTL: 108 0 33
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error occurred while writing: 1079283616
Error while reading midi 9
Error while reading midi 9
Error while reading midi 9
Bela stopped

giuliomoro

hmm that's interesting.
The issue with hotplug USB is known and depending on the kernel in use.
See here. Solution is: plug the device in before you power up the board. Be aware that the board cannot provide a huge amount of current through the USB port, especially when it is powered through the USB port itself. If you have multiple external devices connected to a USB hub you may have to use a powered USB hub.

Let me see if I can do anything for the other errors you are getting. I merged things together in the dev branch last night and haven't quite tested them thoroughly yet. What branch are you using?

jeppius

ok I will try that. I used the link you provided me
https://github.com/BelaPlatform/Bela/tree/5e067bb538d5a36b7a2b392a8e352bcc0ac02479
I can update it to whatever branch you suggest me.
By the way, the file default_libpd_render.cpp should be edited prior to updating the Bela (that is, editing the zip file) or once updated, trough ssh?

giuliomoro

Those errors I see on your log above could well be due to an underpowered board or USB hub, I think I have seen them before .

I can read/write with no troubles on two devices (M-audio Axiom Mini air32 and Rebel Tech Owl Pedal, Bela powered from the barrel connector and the two devices connected to a passive USB hub. Note that when I was powering the board through the USB port, it refuses to boot because I was draining too much current from the USB port!).

From the strings in your error messages I'd say you are not using the latest dev branch. I also improved the error reporting just now. Please update to the dev branch and report back if you are still having problems.

giuliomoro

Yes I guess the trouble is with your power, that commit should just work I believe.

You need a custom render file in your project, as in the examples/08-PureData/customRender .
The easiest way to start with that is:
- update your image
- create a project called projectName
- on the console in the IDE type:

cp core/default_libpd_render.cpp projects/projectName/

in a few seconds the file "default_libpd_render.cpp" will appear in your project explorer and you can edit it.