On Sun, May 02, 2010 at 02:53:50PM -0400, Paul Alfille wrote:
> > As part of these investigations it seems to me that the parameter
> > 'power' does not actually mean that the device has external power, it
> > means that the ground lead is not connected to the VDD (+5v) lead. Can
> > anyone confirm this?
>
> Power comes straight from the chip's report. You can use either
> whatever you find experimentally, or what the datasheet says.
Please post back what you find here, I'm now switching to a setup with a
poewred hub and some of my devices will be powered, some will not because
it's time consuming to get to them to add power after the fact.
I did some quick test with DS18B20 in parasite vs powered mode.
I indeed found no way from the owfs interface to know if the device is
powered or not, but owfs must know since querying in parasite mode is not
the same code than querying in powered mode.
In powered mode, an average of 10 uncached reads took 0.95s for 12 bits
In parasite, it took 1.35 sec for 12 bits.
I expected the difference to be bigger but I guess not.
But is owfs able to know which devices are powered and send requests in
parrallel to them and get the answer 1 sec later of all of them at once,
while doing parasite ones serially later, or does it just treat them all the
same?
And just to confirm, it owfs does know if an individual device is
powered, does it not?
Marc
--
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems & security ....
.... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/
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