Re: [LAU] Problems with usb midi cable

On Thursday 18 June 2009 11:24:04 Denis A. Altoé Falqueto wrote:
> On Thu, Jun 18, 2009 at 4:57 AM, Clemens Ladisch<cladisch@email-addr-hidden>
wrote:
> > Denis A. Altoé Falqueto wrote:
> >> I've bought a (el cheapo) midi-usb cable so I can play my musical
> >> keyboard (also el cheapo... but I'm no professional :)). The thing is
> >> that when I try to use it in my laptop (Gigabyte W566U, ArchLinux 64
> >> bits, up to date), it is not reliable. I play the keys and the midi
> >> events are not delivered correctly. I'm using aseqdump to debug. For
> >> example, I press 5 keys and see 5 key down events, but when I releas
> >> them, only 2 o 3 note up events are shown. And if I play too many
> >> notes, it just stops receiving any events from the device, dmesg show
> >> a strange message "urb status -75" and reconnects the usb device.
> >
> > Is there also a message when single events are lost?
> >
> > 75 means EOVERFLOW. linux/Documentation/usb/error-codes.txt says:
> > | -EOVERFLOW (*) The amount of data returned by the endpoint was
> > | greater than either the max packet size of the
> > | endpoint or the remaining buffer size. "Babble".
> > |
> > | (*) Error codes like -EPROTO, -EILSEQ and -EOVERFLOW normally indicate
> > | hardware problems such as bad devices (including firmware) or cables.
> >>
> >> I tested the same cable on my old desktop (Asus A7N8X-X motherboard,
> >> nvidia MX440 graphics card, 5 years of intensive e loyal use,
> >> ArchLinux 32 bits) and it works fine. The difference between the two
> >> seems to be the usb module that handles the device. [...]
> >> Does anyone has any suggestions on how can I force ohci_hcd to be
> >> loaded before uhci_hcd? Or is it realy the problem?
> >
> > ohci_hcd works only with an OHCI controller; uhci_hcd works only with
> > a UHCI controller. Loading the other one will not have any effect.
> >
> > If you really want to try a different driver, connect the interface
> > through a USB 2.0 hub; this will be handled by ehci_hcd. But I guess
> > this won't make any difference.
> >
> > What kernel version are you using on each machine?
> >
> > The ICH8M chip of your laptop isn't known for making USB problems.
> > This might be a problem with a USB port (try another one) or the
> > laptop's wiring.
> >
> >
> > Best regards,
> > Clemens
> > _______________________________________________
> > Linux-audio-user mailing list
> > Linux-audio-user@email-addr-hidden
> > http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
>
> Yeah, that's the case, really. Before I read your email, last night I
> had the confirmation that is a hardware problem with the usb ports of
> my laptop and the usb plug of the cable. I use a usb keyboard (not
> musical) in my desktop and it has also two usb ports in one side. I
> connected the keyboard to my laptop and connected the midi cable in
> one of the usb ports of the keyboard. The uhci_hcd module was loaded
> and no notes were lost. Another thing that happens is that only 2 usb
> ports out of 4 of the laptop work with the midi cable, being that one
> of them gives miscontacts (I need to force the cable into the port and
> any sudden movement makes it disconnect).
>
> I thank you all for your time. The sense that we don't know what is
> wrong is very annoying, but now I can at least decide about something.
> Maybe I should buy some decent midi interface :)

Sounds to me that some of your usb ports are worn out, though.
If you look at the construction of usb ports carefully, there's four little
pieces of metal that have to push agains the four pieces of metal inside the
plug. If the ones inside your laptop's usb port are worn out, that could cause
the behaviour you're mentioning. Especially if your device is powered from the
usb port (which seems to be the case). If the 5V lead is miscontacting, this
will power up/power down your device at will, if the manufacturer decided to
save money on the little capacitor which could remedy this problem.

sincerely,
Marije
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Received on Fri Jun 19 00:15:01 2009