On Mon, Jan 11, 2010 at 10:02 AM, Sophana K <[email protected]> wrote:
> On Sun, Jan 10, 2010 at 11:10 PM, Paul Alfille <[email protected]> > wrote: > >> Some sensors are powered some are not. > > > > > > That might be a problem. There isn't enough current in the data line to > fuel > > simultaneous parasitic-powered temperature conversions. > > It is not really a current problem. The data line must be held high > during all the temperature conversion. So it is not possible to access > any other device during the conversion > > >> > >> My big problem I had: I don't have the /simultaneous directory when I > >> "ls" in the owfs directory. But when I do 'ls simultaneous', the dir > >> exists! > >> > > > > The directory is only listed when there is a relevant device on the bus. > > (But the directory is valid, just hidden). I was perplexed until I saw in > > the next section that you have a DS2409 microhub. > > > So this is not a bug? > Maybe it should appear at each hub "aux" and "main" dirs? Exactly! > > > Thanks for the report. Sounds like a bug. > Thanks for your support. > > I would also have a feature wish concerning this. > As I said, I have some sensors that are not powered but all alone on > their own bus segments behind the hub. > Is it possible to make an asynchronous read? > This means make simultaneous reads but between distincts hub segments, > as if there were several 1 wire bus controlers. > I don't know if it is electrically feasible, but I think it should. > It's easy to do if the segments are on different bus masters. Just read in a different thread or program since only the bus master is locked. An asynchronous read property for temperature is also possible. > Maybe it could look something like a temperatureReadTrigger in each > sensor dir. This would start the conversion process, and lock the bus > segment until the conversion ends. During this time, other hub's bus > segment should remain accessible and it should be possible to start > other temperature conversion on these other bus segments. > A read in the corresponding temperature file would wait until the > required conversion time is finished. > This should work even if sensors are not powered. > But if they are powered, it should be also possible to trigger several > simultaneous sensor read in differents hub's buses. > > What do you think about this? > Yes. This would work. This is actually fairly similar to how the simultaneous property works.
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