Detecting USB devices at startup?

[Bernd Walter]

On Tue, Nov 06, 2007 at 12:01:50PM +0200, Krassimir Slavchev wrote:
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> Hi,
> 
> M. Warner Losh wrote:
> > In message: <472F1A97.3090308 at bulinfo.net>
> >             Krassimir Slavchev <krassi at bulinfo.net> writes:
> > : At boot I get:
> > ::: doesn't
> > : But if I unplug and plug the usb device:
> > ::: works
> > : Any ideas why this happens?
> > : PS1: I have this problem with all USB devices I tested.
> > 
> > This may be a power issue.  I've been running a KB2902A for months
> > with -current with various types of ucom devices that are seen at
> > boot without the hotplug.
> > 
> > Maybe you can try adding a powered hub and seeing if that helps.
> > 
> > Warner
> > 
> 
> Yes, It looks like a power issue but the power supply used in the
> development board is very good designed (LM2576 is used). I will measure
> power line again. Also the PWM frequency might interfere with PLL.
> I will try to find powered hub to make tests. All usb hubs on the market
> are bus-powered :(

I can ensure you: there are self powered hubs.
If in doubt buy a seven port, they can't work bus powered.

Is the LM2576 really used for USB?
This is a very beefy thing just for a single port and everything else
in a AT91RM9200 system is running at 3,3V or lower.
On my board I use such a 257x regulator for 3,3V, separate linear
regulators from 3,3V to supply the 1.8V for core and switch and
another linear regulator directly from input for 5V to USB.

-- 
B.Walter                http://www.bwct.de      http://www.fizon.de
bernd at bwct.de           info at bwct.de            support at fizon.de