Hi,
[EMAIL PROTECTED]:
> The problem is that sequential samples of the DS indicate to me that I'm
> not actually getting updated information, just the same thing I got last
> time.
That's by design.
> A: is there a way to force new acquisition with each request?
if you do a "ls /mnt/1wire" you see a couple of special directories. One
is named "uncached". That should be evocative enough ...
> B: would +5V external rather than parasitic powered DS help?
Well, somewhat. The point is that if you use external power the
converter will tell the host when it's done. Otherwise you have to
wait however long a pessimistic estimate of the conversion time is.
My own measurements were measurably different (and more jittery) with
parasitic power, so I decided not to use it anywhere if possible.
(Some of these devices manage not to *have* a +5V input...)
> C: is a two-second cycle time too short?
>
Well, if I applied a two-second cycle time to all of my devices I'd need
about ten USB interfaces... :-/
The question is, how fast does your input change, so that you need the
quick updates to make your algorithm behave correctly?
> The software is C; I'm using fopen and fscanf to
> acquire the contents of /mnt/.../temperature and work with the results.
You might want to use one of the provided libraries instead.
It's much faster and depends on fewer pieces of software you might not
really need, or want, in a production environment.
--
Matthias Urlichs | {M:U} IT Design @ m-u-it.de | [EMAIL PROTECTED]
Disclaimer: The quote was selected randomly. Really. | http://smurf.noris.de
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