[LAU] Problems with usb midi cable

[Clemens Ladisch]

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