Windows XP (and previous versions) have difficulties dealing with two identical USB devices. Please see this semi-technical discussion at one of the Windows developer's blogs. http://weblogs.asp.net/oldnewthing/archive/2004/11/10/255047.aspx -Ben Allison > From: "Bert Schiettecatte" <bert@xxxxxxxxxxxx> > Subject: [wdmaudiodev] Re: USB midi driver? > Date: Wed, 24 Nov 2004 00:47:28 +0100 > > Hi, > > Actually, it does. Every system exclusive message has a manufacturer's > identification code. An app that knew it was getting multiple devices > on separate MIDI controllers could distinguish them by using that. > > That won't work. There is no way you can tell the difference between two > control messages being sent. You can't tell from which device the > message is sent because they look identical, apart from the control > value. System exclusive is only used to transfer device configuration > settings, etc. Of course you can use sysex to send a unique serial > number, but that's really a dirty hack. I would rather have Win XP > assign unique names to both devices, e.g. : > > midi devices > |- midi controller #1 > |- midi controller #2 > > The question in my mind is this: what do you mean by "distinguish" > them? Windows will certainly let you plug in two identical devices, it > will load drivers for the two devices, and it will expose interfaces for > both devices. An application that enumerates all the MIDI devices will > find two of them, with different device IDs. If the app KNOWS there > will be two different devices, it can open one instance to each. > > I am not sure Win XP will allow you to connect 2 identical devices or it > will support 2 of these devices at the same time. Even if it allows you > to do that, it will assign identical names (and different IDs like you > said) to the devices. Which might confuse MIDI software that was not > properly designed and uses names to distinguish between devices. > > How would you EXPECT to be able to distinguish them? Describe for me a > use case in which this is important, and how you visualize things > working. > > suppose somebody buys two identical midi devices. he arrives home, knows > what he is doing, installs the drivers first, then plugs in both > devices. suppose he is lucky and Win XP shows 2 new midi devices with > identical names in the hardware list (control panel/system). > next he starts his favorite MIDI application which lists 2 identical > midi devices. no way to tell which physical device corresponds to which > name in the combo box! now, there is no way for the user to know where > he is sending his controller messages each time he has to select the > device in some combo list (and this happens many times in pro audio > applications). so he has to use trial and error each time he needs to > select the right device from some list, to find the device he actually > wants to send data to. now, imagine he buys 4 of these identical > devices, can you imagine how cumbersome this becomes? > > bert ****************** WDMAUDIODEV addresses: Post message: mailto:wdmaudiodev@xxxxxxxxxxxxx Subscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=subscribe Unsubscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=unsubscribe Moderator: mailto:wdmaudiodev-moderators@xxxxxxxxxxxxx URL to WDMAUDIODEV page: http://www.wdmaudiodev.de/