Re: [Owfs-developers] How to Use Simultaneous

[Paul A. <pau...@gm...>]

Your second use i the correct one.

Write "1" to simultaneous to trigger a conversion. That also clears the
cache. A normal read will read immeadiately the already measured temperature
ready in the device.

Paul Alfille

On Sat, Jul 12, 2008 at 8:28 PM, Doug Collinge <dou...@gm...>
wrote:

> I'm writing myself a little Python code here and trying to use
> 'simultaneous' but getting results that are inconsistent with my
> understanding.
>
> I have multiple DS1820 devices on a bus.  They are all powered devices.  I
> want to simultaneously convert them all, wait, then read them all.  I'm
> expecting that when I go to read them, since I have signalled a simultaneous
> conversion, that they will all be already converted and ready to send their
> data, .except perhaps the first one if I haven't waited long enough for the
> conversion.
>
> I'm writing a 1 to '/simultaneous', processing some other stuff, then
> reading them all.  If I read from '/uncached/temperature' it takes
> 600-some-odd milliseconds to read each one, which sounds like they are all
> doing a fresh conversion.  If I read from '/temperature' then I get them
> read in much faster but I don't get a fresh conversion each time.
>
> What I want is for writing to '/simultaneous' to always kick off a fresh
> conversion of all the devices so that I always get a new sample when I read
> them, and never take data out of the cache.  How can I accomplish this?
>
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