Is USB shared?

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MrGlasspoole
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Is USB shared?

Unread post by MrGlasspoole » Tue Jan 07, 2020 8:48 pm

Are the 4 USB ports shared with something or among themselves?

I have the same question on the 2 USB 3.0 ports on the ODROID-XU4.

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odroid
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Re: Is USB shared?

Unread post by odroid » Wed Jan 08, 2020 10:15 am

Yes, N2/C2/C1 4 x USB host ports share one root host. The OTG port has a separated 2.0 root though.

The XU4 (Exynos-5422 SoC) has three independent USB root controllers.
The first USB 3.0 root is connected to the Gbit Ethernet bridge controller.
The second USB 3.0 root is connected to the 2-port 3.0 hub controller.
The the third USB 2.0 root is connected to the USB 2.0 host port.

MrGlasspoole
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Re: Is USB shared?

Unread post by MrGlasspoole » Wed Jan 08, 2020 10:55 pm

Hard decision.

I have this problems with my C2 and DVB-S USB tuners:
viewtopic.php?f=181&t=36136&start=50#p276907

And i found this:
viewtopic.php?f=181&t=36136#p267485

So does the XU4 also have USB problems?

I did read the XU4 can do 1200 Mbit/s USB 3.
From the RPi 4 forum: All four USB ports are connected to a single PCIe lane with 4Gbps bandwidth.

So RPi 4 or XU4 because i need stable working USB...

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mad_ady
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Re: Is USB shared?

Unread post by mad_ady » Thu Jan 09, 2020 1:08 am

XU4's usbs are much better in quality than C1/C2. All boards did show some usb stability issues in the past, but I'd rank xu4 as the best, followed by n2 (still has tuner issues), c2 (sometimes corrupts usb frames snd needs retransmissions) and c1 (loads of issues).

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Re: Is USB shared?

Unread post by MrGlasspoole » Thu Jan 09, 2020 11:17 am

Why does every device have USB problems?
From all devices XU4 is best but still not without problems?

Now i found out that it seems like you can't use the full USB 3 bandwidth on the RPi 4 if you connect USB 2 devices (then you only get 480 Mbps).

I can't believe that it's so hard to find a SBC for such a simple thing like connecting multiple USB devices.

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Re: Is USB shared?

Unread post by elatllat » Thu Jan 09, 2020 12:15 pm

For me the rpi needed 2 software patches, the XU4 physical contacts needed cleaning, The N2 needed a software patch, but they all worked with ~10 USB plugged in. The current N2 issue with tuners I suspect is a latency issue unrelated to USB but that's TBD.

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Re: Is USB shared?

Unread post by mad_ady » Thu Jan 09, 2020 5:43 pm

I haven;t had issues with the N1/rockchip devices, but I've used mostly storage.
XU4 had some driver stability issues on high throughput in the old kernel 3.10 days

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