|
I changed my bash script to set simultaneous then
read the voltage / Temp from cached data. This HAS improved my "noisy"
readings by 50%.
See attached trend, from Monday
night you can see an improvement. The 8:00am slight dip is becaouse
the sun shines on my pressure transducer. Don't know if its also
solved my missing data problems too early to tell yet.
More Filtering options I am thinking about
:
A/ I have also noticed that Volt.All
Does NOT have the same values as Volt.A Volt.B Volt.C Volt.D. I thought it
maybe one scan behind however they are always slightly different. On
that basis it must be doing two conversions thus I may try and average the
Volt.All (1st value) with the Volt.A to provide some averaging which
would provide some filtering however not load my SLUG (NSLU2) too much
;
B/ I think a better solution maybe to cron
start my script every two minutes and the script to loop 5 times which would
gather data from 10 devices and average the data over that 5 seconds then
save the results. Is there a recommended limit on retrieving data ..
ie 1wire devices / second.
Any thoughts on the above options ?
cheers
----- Original Message -----
Sent: Monday, November 06, 2006 3:03
PM
Subject: Re: [Owfs-developers] Fwd: [owfs
- Help] DS2450 and the NSLU2 (SLUG)
Simultaneous uses a known "trick" of the 1-wire
system.
Normally you address a specific device before sending a
command. All the other devices drop off and stop listening.
If there is
only one device on the bus, you can use the special 0x33 command that
addresses it.
The convert command for temperature is only recognized by
appropriate devices, so using 0x33 on a crowded bus will set every device
listening, and all potentially converting. Only temperature sensors will
actually do anything with the command. They will all start temperature
measurement simultaneously, and all share the same delay.
Same for
voltage. (Different "convert" command.
Caveates -- needs a lot of
power, so parasytic is unwise.
Can't be in different DS2409
branches.
Timing can get complex if more than one program is accessing the
bus.
The other data from the devices is not affected -- but usually
don't require a significant delay.
Note the DS2438 can measure voltage on 2
channels, but not simultaneously. Humidity measurements won't be sped up by
"simultaneous".
Paul Alfille
On 11/5/06, Serg
Oskin <[EMAIL PROTECTED]>
wrote:
It
starts procedure "convert" on all devices on the bus - hence it actually
only
for values volt* and temp*.
While read from simultaneous/volt
value "1" (time of it is set by cache-options)
procedure "convert" is not
started at data reading from device/volt*. Here an
example of my script
for the program similar rrdtool:
[ -f $Base/simultaneous/temperature
] && {
sim=`cat
$Base/simultaneous/temperature`
if [ "$sim" = "0" ]; then
echo 1
>$Base/simultaneous/temperature
fi
}
val=`cat $Base/$dev/temperature`
It allows very quickly to
obtain data from such quantity of gauges:
# ls -d /mnt/1wire/28.* |
wc -l
77
#
:)
Rob Conway wrote:
> Serg &
Paul,
>
> I use powered devices so I have updated my script to
set
> simultaneous/voltage and temp to 1 then read all device data
out
> of cached data. crontab was also starting a rrdtool
trend script at the
> same time as my 1wire read
script. It seemed to work OK however I put a
> sleep in my
rrdtool script such that my 1wire script can complete first.
>
>
Question: does setting "simultaneous/volt & temp" to 1
initiate a
> reading of just the volts (I assume Volts.all &
volt.x) and temp
> parameters or all data from the
devices.
>
>
cheers
>
|
-------------------------------------------------------------------------
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done quickly with pre-integrated technology to make your job easier
Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
_______________________________________________
Owfs-developers mailing list
Owfs-developers@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/owfs-developers
