On 11/5/06, Serg Oskin <[EMAIL PROTECTED]> wrote:
Serg is correct. The fastest method, especially if you have "power" (rather than parasytically powered) devices is the initiate all the temperatuer and voltage conversions, then read the cached results.
As an anternative, especially if unpowered, there is a benefit to reading uncached/volts.ALL, and parsing the result in your script. The time required is 1 fourth of the individual readings.
Many people have written about doing Serg's technique within the same Cat5 cable, using a separate pair for the to and back.Rob Conway wrote:
> In an attempt to optimise the 1wire communications can you comment on
> the following:
>
> *Reading data*
> My current requirment is to read the volts every two minutes (although
> would like it faster especially when I get my weather station) from all
> channels of 2 x DS2450 (A/D), temperature from 4 x DS18B20, counter
> readings from 1 x DS2423 (counter) and read/write 4 x DS2406 (Switch).
>
> It is very convienient to use awk as I can do some calcs as well, all in
> one line.
>
> My script currently just uses individual awk lines for each
> "uncached/Volt.X" parameter....
> Would it be better for the first line to get uncached/Volt.All and
> subsequent lines to use cached/Volt.All. I think awk will allow me to
> use $0, $1,$2,$3 for each of the values in Volt.All. I "assume" the
> first line /"uncached/Volt.X"/ would cause a direct read from the device
> and the three subsequent reads to /"cached/Volt.X" /would simply get the
> last scanned data from cache and not cause additional traffic. Is this
> correct and a better utilisation of owfs.
Before data reading from DS2450 execute a command:
echo 1 > simultaneous/voltage
and then read cached data.
Serg is correct. The fastest method, especially if you have "power" (rather than parasytically powered) devices is the initiate all the temperatuer and voltage conversions, then read the cached results.
As an anternative, especially if unpowered, there is a benefit to reading uncached/volts.ALL, and parsing the result in your script. The time required is 1 fourth of the individual readings.
>
> *Network topology*
> Is there a "1wire mail list" I can post my network topology or can this
> group assist, and get some feedback.
>
> I have a DS9490 running cat5 cable 30 metres to a simple junction point
> (soldered connection point). From this point I go to 4 devices which
> are ~2 metres and another six devices which are another 10 meters away
> which are in series. A future weather station is also desired which
> would include another 5 devices
>
>
> NSLU2--[DS9490]<-----------(30m)--------------->|<-----------------(10m)--------------->[DS2450]<---(3m)--->[DS18B20]
>
> | |
>
> | |
> <---1m)--->[DS2406]-[DS2406]-[DS2406]-[DS2406]
>
> |---(2m)---[DS2450] A/D
>
> |---(2m)---[DS18B20] temp
>
> |---(2m)---[DS18B20] temp
>
> |---(1m)---[DS2423] counter
>
> |----------------------(/Future stub 15m/)--------------------[1wire
> weather station upto 5x1wire devices]
>
> At the 30 metre junction point I am going to install a proper junction
> box with screwed terminals for the devices. should I install some 100
> ohm resistors, and/or capacitors on the stubs ?
One-wire is "BUS" and I strictly do not recommend to do on it branch! Hindrance can be very great!
It is better to double length of wires (see picture).
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