USB unplug time for reset

Werner Almesberger werner at
Tue Mar 1 11:45:49 EST 2011

One way to reset the Ben is by removing the battery, disconnecting USB,
waiting a few seconds, and then connecting USB again.

There's been a bit of disagreement over how long "a few seconds" should
be. Based on experience but without actually measuring things, I
suggested something in the order of 20 seconds, while others found this

I now measured the reset time on three Bens. This was done by just
unplugging USB while watching time pass on a watch. The error margin
should be about +/- 1 second.

Ben "#3"	10 seconds
Ben "#4"	highly variable, sometimes as little as 6 seconds did
		work, at other times it needed 10 seconds.
Ben "#5"	11 seconds

This short experiment suggests that one can be reasonably sure a reset
does occur if unlugging USB for at least 12 seconds. If counting time
without the help of a watch, one should add 10-20%, because impatience
may shorten the subjective seconds a little.

What is also clear from this is that just unplugging and immediately
inserting USB will not work with the Ben.

- Werner

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