Re: [Help 1/2] MUSB: ZiO! CF card reader will trigger a change from MUSB host mode to MUSB peripheral mode

[David Brownell <david-b@pacbell.net>]

On Thursday 10 April 2008, Bryan Wu wrote:
> >  And for our development board EZKIT548, it can provide 500mA current
> >  at 5V as it claimed in manual
> >  with a external regular. So from my point of view, this bug is not
> >  related with 100mA current limit issue.

It's *supposed* to be able to provide that much ... steady
state.  But the issue here is current spikes that cause the
voltage to drop too low.

Did you stick a scope on that signal and *verify* that the
voltage never dropped below the valid level?


> These days I tried hard to workaround this issue, but failed:
> 
> - When VBUS_ERR happens in OTG_A_HOST state and the OTG is in
> peripheral mode, I try to start a new session and power on VBUS.
> - CONNECT IRQ fired and OTG is switch back to host mode.

It needs to re-enumerate at this point, including USB reset.


> - In CONNECT IRQ handler, I rescan the musb->endpoint[i].in_qh or
> musb->endpoint[i].out_qh. Then resume the urb transfer which was
> stopped by the wrong VBUS_ERR mode switch IRQ. or just dequeue the urb
> to call off the transfer.
> - But the ZiO does not reply anymore. No IRQ from USB hardware. World
> keeps silence.

That's compatible with the voltage actually dropping too low,
so that the peripheral AND host see the session as broken.

Sometimes it can help to put a powered hub in between the
musb host and the peripheral ...

- Dave




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