Thanks for the information.  My intention was to operate at full-speed since our demands for data rates are low and it avoids issues associated with higher speed signals, but it may be that I interpreted the USB specs of downstream devices incorrectly (I haven’t engineered USB circuits before).  They are supposedly full-speed compatible but I will check further.


I will look into the USB2504.  Thanks.


Eric Crossley

From: Leandro Lustosa [via Gumstix] [mailto:[hidden email]]
Sent: Wednesday, December 19, 2012 12:15 PM
To: Crossley, J. Eric
Subject: Re: Embedded USB hub




Keep in mind that TI TUSB2046 USB hub (or TUSB2046B) device is only full-speed and low-speed compatible. Check whether your USB device is 1.1 or 2.0.


I mainly see two differences between USB computer and gumstix implementations:


1. Gumstix seems to have issues in powering devices and calls for self-powered hubs;

2. Gumstix seems to acknowledge only high speed devices, i.e., not backwards-compatible. It seems to me that the USB controller lacks transaction translators.


Our team is currently implementing a solution based on usb2504A: it has a self-powered configuration option and it has a transaction translator that should eliminate all problems.




Leandro R. Lustosa, M.Sc.

Department of Systems and Control
Instituto Tecnológico de Aeronáutica - ITA
São José dos Campos - SP- Brasil
Tel.(Cel): +55 12 8195-7651


Message: 6
Date: Wed, 19 Dec 2012 08:48:51 -0800 (PST)
From: Eric Crossley <[hidden email]>
Subject: Re: [Gumstix-users] Embedded USB hub
To: [hidden email]
            <[hidden email]>
Content-Type: text/plain; charset="us-ascii"


I guess some more information is in order.

The short answer is that it is tied to +5V on my custom board.

Long story is that the hub device is paired with a power control switch  (TPS2041) for downstream devices. The PWRON and OVRCUR I/O is configured for ganged mode and so all the +5V to downstream devices is switched as a group.  I don't use the USBH_CPEN signal to do the power switching and instead use the hub and switch combination and I initially had the +5 to the USBH_VBUS attached to that +5V output .  When the hub device did not work (did not assert the PWRON signal outputs) I thought maybe it needed to have that +5V in place to communicate with the hub so I white wired it so that USBH_VBUS always has +5V.
Eric Crossley
From: Keane, Ben (STRX) [via Gumstix] [mailto:[hidden email]]
Sent: Tuesday, December 18, 2012 6:49 PM
To: Crossley, J. Eric
Subject: Re: Embedded USB hub


What have you done with USBH_VBUS (Pin 32 on the J4 connector - if you copied something like the chestnut43 board) line on your custom control board? I believe this needs to be pulled high to 5V so the gumstix knows there is something connected downstream (like your hub).


-----Original Message-----

From: Eric Crossley [mailto:[hidden email]</user/SendEmail.jtp?type=node&node=4966280&i=0>]

Sent: Wednesday, 19 December 2012 8:47 AM

To: [hidden email]</user/SendEmail.jtp?type=node&node=4966280&i=1>

Subject: [Gumstix-users] Embedded USB hub


I am trying to use a TI TUSB2046 USB hub device on a custom expansion


to provide extra USB ports to an Overo gumstix board.    It is not working.

Removed the gumstix board from the expansion board and tacked on a cut

USB cable and connected to computer USB port (without connecting 5V

power since expansion board has its own power).  This worked and saw USB

devices on downstream side of the hub pop-up.  What is the difference

between the gumstix implementation of a USB host and the computer's






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