On 12/15/2011 10:44, Nick wrote:
Please forgive the long post and bear with me on this one.
My first 1-wire network, snaking around the house with 10 or so sensors and
over a long distance, has been a great success. Almost faultless performance
apart from total data corruption for a short while a couple of times that I
think were from a leaky shower putting water on the outside of part of the
run. I took care over the design and used Clipsal pink cat 5, and it seemed
very robust despite many joins and spurs of several meters in some cases,
many other cables of data and power around, damp walls and perhaps other
impediments. I knew that the networks could be fragile, but it seemed that
in practice they would be pretty reliable based on the experience at home.
I was wrong, as imagine my surprise when a simple network of about 50 meters
or so in my office building with one 18b20 on the end was almost a total
failure.
I tested the same setup at home using the same cat 5 and a long run of cable
and had zero errors. Halving the run in the office made no difference, and
while a very short run to a sensor was fine, add on the rest of the run and
it failed again.
After fiddling a little and getting nowhere, I brought in my laptop, LA and
some other kit to the office to explore more. Curiously, with my Dell laptop
(and same LinkUSB master), the network was now 100% reliable. Plugged into a
different Dell desktop in the office, again a disaster. Default wiring was
orange power, white/orange earth, blue data. Others unconnected but wired in
the RJ45.
I agree with the discussion on "ground" and note that, as an experienced
engineering friend has said many times, "there's no such thing as a ground".
One thing that comes to mind.. is yours a parasitically-powered network?
COM ports tend to differ. You might look to see if there is sufficient
drive on the one wire to properly power the network from one COM to another.
If this is inconclusive, try powering your 1-wire network rather than
use the parasitic mode. If this clears it up, perhaps the solution will
follow.
/m
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