nice =] thanks paul! 2011/2/5 Paul Alfille <[email protected]>: > OWFS does use the simultaneous conversion technique, if possible. My > understanding is that simultaneous does not work in passive power > mode. > > There are some subtleties: > 1. The simultaneous is bus-specific. I.e., each bus-master is sent a > simultaneous request and if there are no passive sensors, the > match-rom/convert is done. > 2. The time of the last simultaneous is recorded, and all cached > temperatures are dumped. > 3. When a temperature is then requested, if there is a valid > simultaneous for that bus, we pause until it's a full conversion time, > then read the temperature and store it in the cache with the remaining > time. > 4. A request for uncached works as normal and doesn't interfere with > the rest of the temperatures. > > You know there are alternative temperature sensors that are much > faster, like the DS2438 or the new EDS0071 with RTD or a thermocouple > or any of the BAE devices, or the Hobby Boards UVI device. > > Paul Alfille > > On Sat, Feb 5, 2011 at 9:43 AM, Roberto Spadim <[email protected]> wrote: >> maybe you should use simultaneous + cached read >> since it can put all temperatures in cache, while you just read 1 temperature >> check source code, but i think that's something like it >> >> 2011/2/5 Roberto Spadim <[email protected]>: >>> i didn't read the code about this skip rom command in owfs, but i >>> think it's just a bit (a file) to change from 0 to 1 >>> and all new temperatures will be read as simultaneous >>> the problem is >>> if owfs just read one file, how could you use this function? you >>> should read 100 files at once, but it doesn't exists (i think) >>> >>> 2011/2/5 Mick Sulley <[email protected]>: >>>> Yes I have seen the 85 degree situation, it happens sometimes if you run >>>> in parasitic mode and do not ground the VDD line, but sometimes it seems >>>> to run happily like that. >>>> >>>> I see the reference in the spec sheet to issuing a Skip ROM command, but >>>> I have no idea how to do that using pyowfs. I guess I need to read a >>>> bit deeper into basic owfs documentation. >>>> >>>> Thanks >>>> Mick >>>> >>>> On Sat, 2011-02-05 at 03:29 +0100, patyrk wrote: >>>>> Dnia 2011-02-04, pią o godzinie 23:34 -0200, Roberto Spadim pisze: >>>>> > i never used simultaneous... >>>>> > but ds18b20 and ds18s20 sometime have a problem (maybe low power or >>>>> > problem on wire, i never founded why) >>>>> > it restart internal cpu (ds1820) >>>>> > and send 85 degree (i don't remember but it's a fixed value) >>>>> > if you get that value, you need read more two times to get the real >>>>> > value >>>>> > i think simultaneous read will make it more problematic... >>>>> >>>>> Just read the ds18b20 specs and found this (page 11) >>>>> http://datasheets.maxim-ic.com/en/ds/DS18B20.pdf >>>>> SKIP ROM [CCh] >>>>> The master can use this command to address all devices on the bus >>>>> simultaneously without sending out >>>>> any ROM code information. For example, the master can make all DS18B20s >>>>> on the bus perform >>>>> simultaneous temperature conversions by issuing a Skip ROM command >>>>> followed by a Convert T [44h] >>>>> command. >>>>> >>>>> So it should be possible to make conversion and the read all >>>>> scratchpads? Is should be much faster. The specs doesn't mention that >>>>> ds18b20 can't be in parasite mode. I think that just blocking the bus 1 >>>>> second will give enough time for conversion to take place. >>>>> >>>>> Now I don't see any performance increase when invoking simultaneous >>>>> before temp. read. >>>>> >>>>> -- >>>>> P4trykx >>>>> >>>>> > >>>>> > >>>>> > 2011/2/4 patyrk <[email protected]>: >>>>> > > Dnia 2011-02-05, sob o godzinie 01:10 +0000, Mick Sulley pisze: >>>>> > >> My sensors are powered, the temperature sensors are a mix of DS18B20 >>>>> > >> and >>>>> > >> DS18S20, I just used DS1820 as a generic term. >>>>> > >> >>>>> > >> Is there a way to use simultaneous conversion with pyowfs? >>>>> > > I don't know pyowfs >>>>> > > but when mounted by owfs there is a >>>>> > > >>>>> > > /mnt/owfs/simultaneous/temperature >>>>> > > >>>>> > > file and I suspect writing 1 to this file trigers the conversion >>>>> > > signal >>>>> > > >>>>> > > >>>>> > > >>>>> > > -- >>>>> > > P4trykx >>>>> > > >>>>> > > >>>> >>>> >>>> ------------------------------------------------------------------------------ >>>> The modern datacenter depends on network connectivity to access resources >>>> and provide services. The best practices for maximizing a physical server's >>>> connectivity to a physical network are well understood - see how these >>>> rules translate into the virtual world? >>>> http://p.sf.net/sfu/oracle-sfdevnlfb >>>> _______________________________________________ >>>> Owfs-developers mailing list >>>> [email protected] >>>> https://lists.sourceforge.net/lists/listinfo/owfs-developers >>>> >>> >>> >>> >>> -- >>> Roberto Spadim >>> Spadim Technology / SPAEmpresarial >>> >> >> >> >> -- >> Roberto Spadim >> Spadim Technology / SPAEmpresarial >> >> ------------------------------------------------------------------------------ >> The modern datacenter depends on network connectivity to access resources >> and provide services. The best practices for maximizing a physical server's >> connectivity to a physical network are well understood - see how these >> rules translate into the virtual world? >> http://p.sf.net/sfu/oracle-sfdevnlfb >> _______________________________________________ >> Owfs-developers mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/owfs-developers >> > > ------------------------------------------------------------------------------ > The modern datacenter depends on network connectivity to access resources > and provide services. The best practices for maximizing a physical server's > connectivity to a physical network are well understood - see how these > rules translate into the virtual world? > http://p.sf.net/sfu/oracle-sfdevnlfb > _______________________________________________ > Owfs-developers mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/owfs-developers >
-- Roberto Spadim Spadim Technology / SPAEmpresarial ------------------------------------------------------------------------------ The modern datacenter depends on network connectivity to access resources and provide services. The best practices for maximizing a physical server's connectivity to a physical network are well understood - see how these rules translate into the virtual world? http://p.sf.net/sfu/oracle-sfdevnlfb _______________________________________________ Owfs-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/owfs-developers
