Compatibility with USB host mode compliant devices

[BenjaminPoilve]

As you know, the minichord only works with devices that support the USB host mode. I've had reports from minichord users regarding its use.

There are some positive example, in which all seems to work quite well:

• Norns (by Monome)
• Organelle (by Critter & Guitar)

But there are also situations in which it seems that the MIDI signals get scrambled for some reason:

• RK006 (by RetroKits)
• H2MIDIPro (by CME)

I currently don't have either of those devices, so it is a bit complicated to troubleshoot what the issue could be. I might need to purchase one at some point. In the meantime, I'd like to use this thread to discuss such issues and hopefully get some helps from people that have more experience on the matter to try to troubleshoot those issues.

[iktomi-sakala]

Hey, I'm really interrested by your Minichord. I have a home studio with some stuff, and even if I consider your instrument already cool by itself, if it would work with some of my synth, it would be really fantastic. (mainly my GR-1 and GR-Mega from Tasty Chips)
I have no expectations, but I think it might work, as they are pretty much "open" in term of connectivity. (based on raspberry, direct usb connection with a Microlab or the Scarlett 2i2 work fine by example, they just need to be class compliant).
I think I'll order you one for what it is anyway (when I can)... and then I'll do some tests, and get back to report what I got.
(j'aurais bien communiqué en français, mais pour le besoin de partage d'info, j'en reste à l'anglais)

[mio-moto]

I have a H4MIDI WC at my disposal and a teensy development setup. I can do some debugging, if you point me in the right directions.

[BenjaminPoilve]

@iktomi-sakala that's very generous of you! If you can indeed report, even just to say that it does not work, that could be very useful (et oui pour partager avec le reste du monde, l'anglais reste la norme :))

@mio-moto currently, simply testing if the signal goes through to activate midi synth would be great. I'm a little at loss at what was causing the issue with RK006: my idea was that it was probably the sysex messages that were messing up with the device, but I made a version of the firmware without sysex and it did not solve the issue. For the rest, I'm using the standard teensy midi library, so USB class compliant, with simple midi messages. Maybe because I'm using two ports?

[mio-moto]

I do get MIDI, but only if I plug in a 3.5mm TRS connector - and it's only the same message.
It shows up as two separate devices, where the minichord-2 device does send any messages (but receives, I guess?)

[BenjaminPoilve]

Since you already are using midiview, you can easily plug the minichord into the computer and check out the expected signals. To sum up:

• Port 1 is the chord section
• Port 2 is the harp section
  Now port 1 also listens for sysex and send some to communicate with minicontrol.
  At least we got a glimpse into the mystery: what are those weird messages.. Thanks for the cap, it'll help me think about it!

[Profitsarts]

Hello.
I bought Minichord and something strange is happening in Ableton Move. It only recognizes MIDI In on Auto. When I test channel by channel, I see that it only receives on Channel 11. The chords and strum work, but it only plays two strange chords and they are always the same, alternating button by button: one does a weird chord , the next another and again, sequentially.
The harp always does the same thing, a chord that should be all the notes at once, almost like the chords.

It works perfectly in Ableton Live.
Can you tell me what the problem might be?

Thank you.

[mio-moto]

When I test channel by channel, I see that it only receives on Channel 11.

this is my experience as well. It worked once, and then never again.

Ok, after testing some, it seems like the device has to be powered on (throug a plugged in headphone jack) and be connected to a desktop first. Then it can be, while being kept powered on, connected to hostable USB devices like the move or H4MIDI and it works temporarily. There seems to be an issue with the MIDI setup on USB when no desktop host is present.

If the device powers on and is connected to just an USB host, it goes into that error state

Bugged:

After restarting and being connected to a desktop first - then to an USB host:

[BenjaminPoilve]

Thanks, that will help me out understanding what is going wrong there !

[mio-moto]

Other issues: Pressing keys on the keypad sends on and off messages weird, looks like the buffer is not sent out when pressing a key, as such pressing the board only sent half baked frames:

Here I've pressed a key down:

then let go

---

Tapping on the board sent more off notes (look at the timestamp, one on message is met with three off messages):

--

A swipe across the board causes a lot of on/off notes, when a stringed instrument would likely (?) do an on message and only do an off on release (or after some times):

---

entering hold mode (top right button), sometimes gets it correct on the board:

but fails on releasing the mode:

[BenjaminPoilve]

Thanks I indeed noticed the double off, that surely is weird. I checked that for sure and it worked as expected, but we did some refactoring, so there could be two issue colliding there. I'll be able to test tomorrow, but by all means, keep those feedbacks coming, it is very helpful !

[mio-moto]

Here is another recording on the M8 Tracker, the first part is tapping on the keyboard, they get released weirdly and then is stringing on the board that does immediate on/offs with an AHD envelope:

2025-10-09.16.32.34.m8-recording.webm

Using an ADSR envelope (such as the note doesn't disappear immediately), makes it a bit better, but shows that swiping along the board only sends the (root?) note:

2025-10-09.16.32.34.m8-recording.webm

Tapping on the keys makes it break in random ways, again.

Sometimes randomly tapping the board gets me other notes than the supposed E-6.

[Profitsarts]

Hi.

Just after writing you, checked on Ableton Note on the iPad, through the camera connection kit USB 3 > Lightning and it worked like a charm. They are supposed to be kind of the same (Move & Note) in terms of MIDI, just my thoughts, not an expert of course.

[mio-moto]

When using the minichord on a desktop systems, the problems go away apparently:

Holding keys on the keyboard works:

Holding strings on the board also works:

there seems to be something (?) that a proper managed desktop operating system does (some serial messages, without libusb + wireshark I can't debug that right now), that USB host boxes don't do. Since the device enable USB MIDI properly without talking to a host before, I'm guessing it's some operating system acknoledgement (per note, perhaps?)

[BenjaminPoilve]

Ah at least you confirm that I did not skimp on testing, it does work as expected ton the desktop. I have a bit of time now, I'll look into the code. Two options:

• I see something fishy and try a fix;
• I don't see anything strange and I'll move to my next suspicion: the multi-port code is not great. I'll then make a single port branch to allow you to test it out!