[wdmaudiodev] MIDI-usb packets Zero padded using WinXP SP2 generic audio-usb drivers

  • From: Bruno PILLET <bruno.pillet@xxxxxxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Wed, 19 Jul 2006 18:26:20 +0200


I am developing a usb midi controlleur, and have a strange behavior with windows XP sp2 Midi usb generic driver. I use a cypress FX2/FX2PL usb high speed chip.

-> Every Usb Midi packet sent is filled with zeros until the size of the OUT endpoint. So the bandwidth of the connection is wasted, and the endpoint byte counter point to the size of the buffer instead of the size of the message itself.
I check with both hardware and software USB analyser.

It does not append on Mac OSx!

So does anybody already noticed such a kind of behavior? Is it normal? Do you have any suggestion to deal with it.
A workaround to determine real packets length is to stop counting on the first USB command egal to zero(not already used in USB spec), but my main concern is the waste of bandwidth because my device is also an audio device with 10 in and 2 out channels.



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  • » [wdmaudiodev] MIDI-usb packets Zero padded using WinXP SP2 generic audio-usb drivers