<div dir="ltr"><div>David,</div>
<div> </div>
<div>Just so you know that it can be done, I used a 7 port USB hub with TT's on each port and filled it with 7 radio channels running simultaneously for a commercial trunking radio system and it works just fine.</div>
<div>The server was a 2.66 GHz Pentium 4 on an ASUS motherboard.</div>
<div> </div>
<div>73,</div>
<div> </div>
<div>Steve Henke, W9SH</div>
<div> </div>
<div class="gmail_quote">On Fri, Jul 25, 2008 at 9:19 PM, David McGough <span dir="ltr"><<a href="mailto:kb4fxc@inttek.net">kb4fxc@inttek.net</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"><br>Hi Everyone,<br><br>Well, I just tried one of the usbgear hubs listed below. It ..almost..<br>works. The 2 URI devices I'm experimenting with are identified and<br>
functional EXCEPT that it sounds like the audio sampling rate is<br>wrong--way too low with aliasing distortion (or something). ugh. Probably<br>a driver confusion issue??<br><br>Anyway, the USB hub and hardware otherwise seems to be fine.<br>
Here is an output from the usbtree utility:<br><br>[root@kb4fxc-rpt ~]# ./usbtree<br>/: Bus 02.Port 1: Dev 1, Class=root_hub, Drv=ohci_hcd/8p, 12M<br>/: Bus 01.Port 1: Dev 1, Class=root_hub, Drv=ehci_hcd/8p, 480M<br> |_ Port 4: Dev 2, If 0, Prod=USB2.0 Hub, Class=hub, Drv=hub/4p, 480M<br>
|_ Port 1: Dev 3, If 0, Prod=C-Media USB Headphone Set, Class=audio, Drv=snd-usb-audio, 12M<br> |_ Port 1: Dev 3, If 1, Prod=, Class=audio, Drv=snd-usb-audio, 12M<br> |_ Port 1: Dev 3, If 2, Prod=, Class=audio, Drv=snd-usb-audio, 12M<br>
|_ Port 1: Dev 3, If 3, Prod=, Class=HID, Drv=usbfs, 12M<br> |_ Port 2: Dev 4, If 0, Prod=C-Media USB Headphone Set, Class=audio, Drv=snd-usb-audio, 12M<br> |_ Port 2: Dev 4, If 1, Prod=, Class=audio, Drv=snd-usb-audio, 12M<br>
|_ Port 2: Dev 4, If 2, Prod=, Class=audio, Drv=snd-usb-audio, 12M<br> |_ Port 2: Dev 4, If 3, Prod=, Class=HID, Drv=usbhid, 12M<br> |_ Port 4: Dev 5, If 0, Prod=USB2.0 Hub, Class=hub, Drv=hub/4p, 480M<br>
<br><br>I'll investigate further since this is ultimately a config I may want to<br>use as well.<br><br>David KB4FXC<br>
<div>
<div></div>
<div class="Wj3C7c"><br><br>On Tue, 22 Jul 2008, David McGough wrote:<br><br>><br>> So, I guess the next question is: Does anyone have a favorite multi-tt<br>> hub? ....I have used this one in the past for other linux applications and<br>
> it seemed okay...I'll try one with the URI's....I guess the biggest issue<br>> here is that the hub you buy today won't necessarily be the one on the<br>> shelves tomorrow....A bit frustrating!<br>><br>
> <a href="http://www.usbgear.com/USBG-217C.html" target="_blank">http://www.usbgear.com/USBG-217C.html</a><br>><br>> -David<br>><br>><br>><br>> On Tue, 22 Jul 2008, David Kramer wrote:<br>><br>> > I have successfully tested URIs with several high speed USB hubs. But these<br>
> > tests were performed without any other USB devices connected at the same<br>> > time so this may not be very usefull.<br>> ><br>> > Skip points out the difference between full speed (12Mbps) and high speed<br>
> > (480Mbs) devices. This terminology is confusing. Not all USB 2.0 compliant<br>> > hubs support high speed, so be sure the package says HIGH SPEED.<br>> ><br>> > Very few hubs support multiple transaction translators, probably because the<br>
> > chip sets are more expensive and almost nobody understands the need.<br>> > Theoretically, one TT is all that is needed provided you don't mix USB 1.x<br>> > and 2.0 devices on the same hub. Keep in mind that USB supports several<br>
> > data modes each with varying priorities and latency allocations. Plus USB<br>> > physical layer is half-duplex so one-way communication never comes close to<br>> > 480Mbps. The TT tries to handle all the traffic so don't expect good<br>
> > results if you plug a bunch of web cams or other bandwidth hungry devices<br>> > into your hub.<br>> ><br>> > Hope this help.<br>> ><br>> > David Kramer<br>> > DMK Engineering Inc.<br>
> > 310-544-1222<br>> ><br>> ><br>> > -----Original Message-----<br>> > From: <a href="mailto:app_rpt-bounces@lists.illiana.net">app_rpt-bounces@lists.illiana.net</a><br>> > [mailto:<a href="mailto:app_rpt-bounces@lists.illiana.net">app_rpt-bounces@lists.illiana.net</a>] On Behalf Of Skip WB6YMH<br>
> > Sent: Tuesday, July 22, 2008 1:22 PM<br>> > To: <a href="mailto:app_rpt@lists.illiana.net">app_rpt@lists.illiana.net</a><br>> > Subject: [App_rpt] USB hubs & USB audio<br>> ><br>> > > Jim Dixon and I have had disapointing results with USB hubs during the<br>
> > > testing of USB fobs with them. We don't know why they don't work<br>> > > properly and we don't have the time to figure it out right now. There<br>> > > may be hubs which work just fine, but we just don't know as the root<br>
> > > cause of the problem has not been uncovered. If Steve Henke W9SH<br>> > > knows something I don't them maybe he should speak up on the list.<br>> > > Steve WA6ZFT<br>> ><br>> > The problem is probably complex. USB 2.0 hubs come in two flavors single-<br>
> > transaction translators (single-TT) and multi-transaction translators<br>> > (multi-TT). Most USB audio devices are "full speed" devices (12<br>> > mbits/sec), not "high speed" devices (480 mbits/sec) so the USB hub must<br>
> > translate the data rate between the host and the device. The single-TT<br>> > devices only have a single translator which is shared between all ports.<br>> > A multi-TT hub has a translator per port. So in theory a milti-TT hub is<br>
> > what you should want for optimal bus usage.<br>> ><br>> > An additional complication is that the Linux kernel must be multi-TT hub<br>> > aware to properly schedule things. I'm not current with Linux<br>
> > development, but I've read discussions in the past about improving the<br>> > kernel's USB scheduler in this area.<br>> ><br>> > Here are a couple of links to info which may be useful:<br>
> ><br>> > <a href="http://www.commsdesign.com/design_corner/showArticle.jhtml?articleID=1650536" target="_blank">http://www.commsdesign.com/design_corner/showArticle.jhtml?articleID=1650536</a><br>> > 2<br>
> ><br>> > <a href="http://www.linux-usb.org/usb2.html" target="_blank">http://www.linux-usb.org/usb2.html</a><br>> ><br>> > 73's Skip WB6YMH<br>> ><br>> > _______________________________________________<br>
> > App_rpt mailing list<br>> > <a href="mailto:App_rpt@lists.illiana.net">App_rpt@lists.illiana.net</a><br>> > <a href="http://lists.illiana.net/mailman/listinfo/app_rpt" target="_blank">http://lists.illiana.net/mailman/listinfo/app_rpt</a><br>
> ><br>> > _______________________________________________<br>> > App_rpt mailing list<br>> > <a href="mailto:App_rpt@lists.illiana.net">App_rpt@lists.illiana.net</a><br>> > <a href="http://lists.illiana.net/mailman/listinfo/app_rpt" target="_blank">http://lists.illiana.net/mailman/listinfo/app_rpt</a><br>
> ><br>><br>> _______________________________________________<br>> App_rpt mailing list<br>> <a href="mailto:App_rpt@lists.illiana.net">App_rpt@lists.illiana.net</a><br>> <a href="http://lists.illiana.net/mailman/listinfo/app_rpt" target="_blank">http://lists.illiana.net/mailman/listinfo/app_rpt</a><br>
><br><br>_______________________________________________<br>App_rpt mailing list<br><a href="mailto:App_rpt@lists.illiana.net">App_rpt@lists.illiana.net</a><br><a href="http://lists.illiana.net/mailman/listinfo/app_rpt" target="_blank">http://lists.illiana.net/mailman/listinfo/app_rpt</a><br>
</div></div></blockquote></div><br></div>