This may be way off topic, but the inrush current problem is probably
with devices not meeting the USB specification. As it turns out, a lot
of low end devices do not meet this spec.
I spent some time redesigning the power supply system of one such device
I was using. This time was covered by the company that built the device,
and eventually it went into production. High speed clamp on probe showed
2Amps inrush, where it was supposed to be much smaller than that. That
caused all sorts of havoc. It worked fine on a PC USB, where the 5V line
is very stiff. USB hubs were a different story.
My bet is a workaround would be a stiff cap (ceramic, not 'lytic) at the
USB on the Pi board to counteract empty filters on the hot plugged
device may help. Maybe a small impedance between the 5V supply of the Pi
board and the cap would help.
Dan
On 5/23/2013 8:37 PM, time-nuts-requ...@febo.com wrote:
"by mahjongg ? Mon Nov 19, 2012 12:09 am
Don't hot plug USB devices directly into the PI, if you must hot plug
plug into a hub instead!
Its called "the rush in current problem", and it makes that the
current PI itself is non "hot pluggable", note that the revision 1 PI
was hot pluggable, as the two polyfuses prevented any rush in current
because the fuses had a non zero resistance. But in the current board
there is literally zero resistance between the PI's 5V supply, and any
USB device you plug in, that means that if you plug in any USB device
with empty power decouplers, (which act as a complete short for a very
small time) then you are actually simply shorting the 5V when you plug
de USB device in.
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
