Author Topic: usb midi spec 2.0  (Read 1783 times)

usbman

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usb midi spec 2.0
« on: November 03, 2021, 10:32:23 am »
Every Spec should support IAD if its released after the IAD spec. At least its stated so in USB Complete. Recently i looked into the usb midi spec 2.0. Not a word about IAD. Its my understanding that every function using more than one interface has to use IAD.

So the question is:
Do i have to use IAD with midi 2.0?
Does usb.org violate their own rules?

Jan Axelson

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Re: usb midi spec 2.0
« Reply #1 on: November 03, 2021, 10:57:23 pm »
According to the IAD spec, a device should use an IAD if the device uses multiple interfaces to manage a single device function.

usbman

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Re: usb midi spec 2.0
« Reply #2 on: November 04, 2021, 05:39:12 am »
Thanks Jan for your response. Thats my understanding too.

I am just wondering why the reference descriptorset in the midi2.0 spec does not contain a IAD descriptor.
It contains a control interface and a data interface, same as the CDC spec.

Jan Axelson

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Re: usb midi spec 2.0
« Reply #3 on: November 04, 2021, 09:59:23 pm »
Don't know, agree that it seems it would merit a mention.

Renate

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Re: usb midi spec 2.0
« Reply #4 on: November 05, 2021, 03:29:51 pm »
IAD came in 2003: https://www.usb.org/sites/default/files/iadclasscode_r10.pdf
USB MIDI 1.0 was updated in 1999?
USB MIDI 2.0 was released two years ago: https://usb.org/sites/default/files/USB%20MIDI%20v2_0.pdf
Oops, no mention of IAD either.

Edit: I should also mention that USB MIDI 1.0 is 43 pages and 167,773 bytes.
USB MIDI 2.0 is 47 pages and 1,595,403 bytes.
And people say that there is no such thing as progress!
(Lots of pointless embedded fonts.)
« Last Edit: November 05, 2021, 03:50:59 pm by Renate »

usbman

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Re: usb midi spec 2.0
« Reply #5 on: November 10, 2021, 04:54:34 am »
ok i have made some tests now.
First I build a device acording the 2.0 spec without IAD. Seems working at least its recognized.
Next I added IAD to it. Again its recognized. Both tests are done under W10.
I just used a basic implementation, to get the device enumereated, no fancy midi stuff.

It seems that at least for W10 IAD does not matter. This seems the same as for CDC. Devices are
recognized regardless of IAD,