jakobmoenster
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Maximum numbers of USB ports

Wed Aug 08, 2012 9:38 am

Hi..

Is there a limit on the maximum number of USB ports the Raspberry Pi can handle.
I.E. is it possible to connect two 7-Port USb hubs (with external power)?

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RaTTuS
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Re: Maximum numbers of USB ports

Wed Aug 08, 2012 9:46 am

possibly should be OK .. what happens when you try ?
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Wendo
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Re: Maximum numbers of USB ports

Wed Aug 08, 2012 9:02 pm

I have a 13 port hub (thats just two 7 port hubs internally) connected no problem.

I doubt there is any limit other than the standard USB limits.

jakobmoenster
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Joined: Wed Aug 08, 2012 9:35 am

Re: Maximum numbers of USB ports

Wed Aug 08, 2012 10:39 pm

Thanks for info. I Haven't tried - I'm still waiting to receive my RPI, (another 6 weeks or so :( ), but I'm shopping for accessories, and the 7 port USB will best fit the case I'll build.

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liz
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Re: Maximum numbers of USB ports

Wed Aug 08, 2012 10:41 pm

As long as it's powered, that should be fine.
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jbeale
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Re: Maximum numbers of USB ports

Wed Aug 08, 2012 11:19 pm

Interesting to hear of a working 13-port hub. Have you tried connecting devices to all 13 ports at the same time, and had them all shown in a lsusb list? Just today, a post from Gordon (gsh) claims that 8 hub ports is the working limit. http://www.raspberrypi.org/phpBB3/viewt ... 78#p145479
Also note that there is a deficiency in the driver which means we're limited currently to a maximum of 8 periodic endpoints, this is because the driver reserves a channel (of which there are eight) for each periodic endpoint. Now I believe that for each hub port you have at least one interrupt endpoint so once you get to seven hub ports then you run out of channels!
I tried a 4-port hub in one R-Pi socket, and daisy chaining two 4-port hubs on the other. That did not work, although each hub did work separately, and I was using external power on all hubs. See also: http://www.raspberrypi.org/phpBB3/viewt ... 28&t=13858 Some 7-port hubs do work. My 10 port hub (which is internally a 7 port hub and a secondary 4-port hub) works in part: the first 6 ports work and the last 4 ports don't. I am powering it externally so that is not a factor.

dom
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Re: Maximum numbers of USB ports

Thu Aug 09, 2012 9:43 am

This issue:
https://github.com/raspberrypi/linux/issues/29
includes a patch that removes the 8 periodic endpoint limit. We've not had enough testers to be sure it is good, but there's been a few positive reports.

Wendo
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Re: Maximum numbers of USB ports

Fri Aug 10, 2012 8:02 am

I'm not sure I _have_ 13 USB devices... I did have to cut the red wire on this hub to get it to behave and not backfeed current to the pi.

I might go hunting for a LOT of USB devices and see what I can get out of it

*edit*

Why yes, you can run more than 8 devices, every USB flash drive I've ever owned, a wireless adapter, a bluetooth adapter, and old MS mouse that doesn't work (but still registers), a _really_ old webcam and a logitech wireless keyboard and mouse dongle


[email protected] ~ $ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 0424:9512 Standard Microsystems Corp.
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp.
Bus 001 Device 004: ID 1a40:0201 Terminus Technology Inc. FE 2.1 7-port Hub
Bus 001 Device 005: ID 7392:7811 Edimax Technology Co., Ltd EW-7811Un 802.11n Wireless Adapter [Realtek RTL8188CUS]
Bus 001 Device 006: ID 1a40:0201 Terminus Technology Inc. FE 2.1 7-port Hub
Bus 001 Device 007: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)
Bus 001 Device 008: ID 0781:5151 SanDisk Corp. Cruzer Micro Flash Drive
Bus 001 Device 009: ID 0930:6540 Toshiba Corp. TransMemory Flash Memory
Bus 001 Device 010: ID 13fe:1f23 Kingston Technology Company Inc.
Bus 001 Device 011: ID 04fc:5605 Sunplus Technology Co., Ltd
Bus 001 Device 012: ID 0951:1602 Kingston Technology DataTraveler Mini
Bus 001 Device 013: ID 090c:6200 Silicon Motion, Inc. - Taiwan (formerly Feiya Technology Corp.) microSD card reader
Bus 001 Device 014: ID 05dc:a575 Lexar Media, Inc.
Bus 001 Device 015: ID 0718:0611 Imation Corp.
Bus 001 Device 016: ID 045e:0047 Microsoft Corp. IntelliMouse Explorer 3.0
Bus 001 Device 018: ID 0c45:624f Microdia PC Camera (SN9C201 + OV9650)
Bus 001 Device 000: ID 046d:c50c Logitech, Inc. Cordless Desktop S510

elatllat
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Re: Maximum numbers of USB ports

Sun Aug 12, 2012 6:06 pm

jakobmoenster wrote:Hi..

Is there a limit on the maximum number of USB ports the Raspberry Pi can handle.
I.E. is it possible to connect two 7-Port USb hubs (with external power)?
The limitation is 14 ports on 2 hubs.
See this thread:
http://www.raspberrypi.org/phpBB3/viewt ... 21#p146421
SBC with 32GB RAM: https://hardkernel.com

FAQ : https://raspberrypi.stackexchange.com

Unanswered: https://www.raspberrypi.org/forums/search.php?search_id=unanswered

jfornango
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Re: Maximum numbers of USB ports

Wed Sep 19, 2012 3:42 am

The USB standard allows for 127 devices.

If I had to guess, I'd say you are having trouble seeing the hubs beyond the first because the root hub can't see the third tier hub controllers through the second tier hub controller. Whether this is a problem with tier two hub, or natural behavior based on the specification I can't say.

If it's an issue, then you should spring for the larger hub.

For the record, I've seen commercial hubs up to 24 ports. On the hacker front, I've seen homemade hubs up to 80 ports (with *huge* power supplies, of course).
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