Piotr, I'm forwarding your note to the owfs-developers list since others may
be able to contribute -- Paul Alfille
On 11/24/07, Piotr Popik <[EMAIL PROTECTED]> wrote:
>
> My "system" is one simple PC with fedora 4, whose only purpose is to
> collect the temperature and possibly, other meteo-related parameters
It produces a web-site with RRD graphs and it works so far, but now I
> needed the solar and the barometer data.
> Digitemp doesn't support the solar (DS2438 "vis"), so I decided to
> give a try to owfs
There is a program written by Tim Sailer that uses owfs for weather data
collection.
http://owfs.org/index.php?page=weather----owfsws
I was looking for a simple tutorial of how to use owfs, but could not
> find it -- everything is so complicated :(
That certainly is a problem. Unfortunately as the only person writing
documentation I am too immersed in the program to really have a good
perspective for a new user. I'll try to write an introductory tutorial if
you can help critique it.
The idea of turning the chip "on" worked, but I needed to use "IAD"
> not "iad". It now reports the voltage of the Vsens -- thanks so much
> for the trick
Oops. Actually, since that worked, I'll have OWFS do it automatically
whenever you try to read vis, I can't think of a reason to read vis with IAD
off.
I'll send you the RRDgraph figure once there will be more data
>
> One last question: shall I run the two commands
> /opt/owfs/bin/owserver -d /dev/ttyS1 -p 4304
> /opt/owfs/bin/owwrite -s 4304 26.DE6EB9000000/IAD 1
> manually each time the Linux restarts or is there a way to do that
> automatically?
Many ways. I'm sure sonone can offer a good init script for Fedora. I've put
the startup code in inittab myself.
Basically, like many of the services on your computer (networking,
filesystems) there are scripts that are started at boot time.
I have to do that as a root -- could not find the way to do that as a
> normal user
Well, the only reason you have to do it at boot is that some things are
protected without explicit permission. Direct hardware access (the serial
port), but that's easy to change. Low port numbers (but 4304 is ok). And
even if you run owserver as root, the programs reading owserver don't have
to be root.
And, more complicated: my understanding is that owfs reports the data
> of a given sensor upon request with
> /opt/owfs/bin/owread -s 4304 26.DE6EB9000000/vis (or:
> temperature)
> BUT, it reads the output more often... every... 30s? Because when I
> repeat the last command in the shell, the readings change after about 30 s
Umm, you've run into data caching.
http://owfs.org/index.php?page=what-is-uncached
Since the 1-wire is slow, many people found that storing the reading
internally in OWFS and only doing a real read every 15 seconds or so made
their programs run much better. Especially if they had more than one program
accessing the same data. You seem to want to force a new read each time, so
read /uncached/temperature and /uncached/vis or set
settings/timeout_volatile to 0.
Because vis data are pretty noisy, i was thinking to average them
> somewhat. This can be done by a script that writes the data into a
> file and averages them and uses the average as the "final" value
> every 5 min (for the weather station). Can this be done internally?
Probably too messy to add directly to owfs. We only read on demand and
either waiting 5 minutes to give an answer, or reading everything in
anticipation seems unwieldy.
You do give me an idea for an "owserver passthrough filtering program" that
would read and average selected values, and pass through all other requests
directly.
Sorry for so many questions, but I hope this will help other people too :)
> Best regards | Piotr
>
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