Adjustable USB host problem

OWL Lich
#1

Hi !

I discovered that if a strong amplification is present in my Puredata patch, it results in a high pitch background noise. (probably a Clock)

After investigating, I found that the noise is coming from my Keystep plugged into the Lich’s USB A host.

I discovered that if I unplug the Keystep, the noise disappears, normal, but if I plug it back in the noise does not come back! :crazy_face:

I am going to do tests on longer usage times today, to confirm that the noise does not come back after a while, but if it does not come back, then maybe by changing the firmware so that the usb device will be powered only after the total start of the Lich could probably solve the problem, well if it is technically feasible of course! :thinking:

Thanks !

#2

Noise probably doesn’t come back simply because USB host stops working after you unplug it and plug back. This is something that would get fixed eventually.

As for “power only mode”, this is not how USB works. When device is plugged initially, the host must provide minimal power and communicate to the device, to negotiate power that it needs and to run enumeration protocol to determine what is connected. This is defined by USB standards.

There are a few threads on this forum with people using USB isolators. But I think that usually they’re used for powering device, while you’ve ran into issues with noise from host. It might still help, I think @mars has one and might measure noise levels if he can reproduce this with some controller.

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#3

I don’t quite understand what you mean by “the usb host stops working after reconnecting it”, but the point is that once reconnected, I can use the keystep and its sequencer without the noise coming back, an hour later the noise has still not returned! :partying_face:

Anyway, it’s not a big deal for me to unplug and plug in it back each time i power on my rack now that i know about it, but I spent a lot of time modifying my patch thinking it came from it ! :rofl:
It’s good to know for the next ones who will be in the same situation as me, that can save up some precious time ! :nerd_face:

Édit: ok i think i got it, you are only talking about the host function !? So I’m going to add a usb midi function in my patch to see if the noise comes back! :nerd_face:

#4

Are you using it to send MIDI or just powering the controller from the USB host? If you use it to provide power only, you should just use a PSU to avoid noise. But reconnecting device to USB host currently causes an error that Martin could solve so far. This prevents MIDI from worker until you reset OWL. The problem is that most of the USB code is coming from official ST Microelectronics library and it’s fairly hard to troubleshoot.

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#5

Yes, you’re right, I’m using the Lich’s usb only to power the keystep and my synth is fed by the Midi for the moment, so I didn’t notice that the host usb function stops after reconnection, but here I have just tested and indeed the midi usb no longer work after reconnection! :crazy_face:
Ok, I can see more clearly now! Thank you ! :nerd_face: