the root cause of flip-flop charging logic if you insert wall charger

Werner Almesberger werner at
Thu Sep 18 06:39:09 CEST 2008

Andy Green wrote:
> | The root cause is the signal from VBUS rasies and drops rapidly when
> | inserting a wall charger.
> It sounds like you were already in Linux doing this, so I wonder what is
> the excuse of the adapter now to drop dead briefly on insertion?

Is this VBUS coming out of the adapter (i.e., measured on the adapter's
cable) or VBUS obtained by the system, i.e., subject to contact bounce
and all that ?

Still, USB detection has a fairly generous debounce time of 62ms, which
should be sufficient.

By the way, Matt, I didn't see your original mail. Could you perhaps
post it here with the pictures (or, if they're too big, put them on
sita aka people) ?

- Werner

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