Can I use OHCI ?

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1

Hi list,

is this possible to use OHCI instead of EHCI as USB host port ?

My goal is to connect a single USB1.1 device directly to the beagleboard w/o using an external hub.

Is this something I can achieve by compiling a custom linux kernel ?

Thanks

2

Nope, its a physical limitation of the IP in the omap35xx..

The xM has a built-in usb 2.0 hub, which would solve your problem/spec...

Regards,

3

Thanks.
That's exactly the kind of thing I was afraid of.
My first though has been that BBoard is physically designed to support usb2.0 only.
Shall I understand that there is an issue in the omap35xx silicon ? The chapter 23.2.1 of of SPRUF98G (TRM of omap 35x) says that OHCI is supported.

4

Good point, i'd never looked at the SPRU document, reviewing the c4
schematic it looks like the smsc usb3322 that causes this artificial
limitation...

either way, to do what you want, use the newer xM, otherwise you'll need a hub..

Regards,

5

Robert Nelson wrote:

6

Vladimir Pantelic <vladoman@gmail.com> writes:

Robert Nelson wrote:

Hi list,

is this possible to use OHCI instead of EHCI as USB host port ?

My goal is to connect a single USB1.1 device directly to the beagleboard w/o
using an external hub.

Is this something I can achieve by compiling a custom linux kernel ?

Nope, its a physical limitation of the IP in the omap35xx..

are you sure, afaik you can use OHCI *or* EHCI on the 35xx, but not mix.

TRM says "Each of the three external ports is owned by exactly one of
the controllers [EHCI,OHCI] at any time."

7

M�ns Rullg�rd wrote:

Vladimir Pantelic<vladoman@gmail.com> writes:

Robert Nelson wrote:

  Hi list,

  is this possible to use OHCI instead of EHCI as USB host port ?

  My goal is to connect a single USB1.1 device directly to the beagleboard w/o
  using an external hub.

  Is this something I can achieve by compiling a custom linux kernel ?

Nope, its a physical limitation of the IP in the omap35xx..

are you sure, afaik you can use OHCI *or* EHCI on the 35xx, but not mix.

TRM says "Each of the three external ports is owned by exactly one of
the controllers [EHCI,OHCI] at any time."

IIRC early OMAP3 revisions had an eratum that prevented the per port selection
of EHCI vs OHCI. But, using one single port as OHCI should work on all...

8

usb3322 does not support Low or Full speed devices! Read the respective datasheet carefully. So, you won’t be able to connect any 1.1 devices to Beagleboard directly, and this does not connected with OMAP3 capabilities.

2010/9/28 Vladimir Pantelic <vladoman@gmail.com>

9

you can connect them to otg directly

10

The signals fromf the processor that support the OHCI port are not accessible on the board. Therefore you cannot use it unless you change the design of the board. It is not a processor limitation.

Gerald

11

Now I know why I bother with a hub !

Thank you all for the clarification.