Hi Paul, Thanks for the response. You are correct, for a DS18B20 it is 94ms. The 10ms data is for the temp read on the DS2438's at 13bits.
Unfortunately I bought a bunch of the Hobby Boards temp boards and didn't notice they don't provide power to the DS18B20's, so I am stuck with parasite power even though there is power available on the wire :( I am considering sending off my own board design to be fabbed as I haven't found one I am happy with. Because of this, it's my understanding that simultaneous conversions will not work, which was confirmed by my testing. Thanks! -Guil On Sun, Jan 23, 2011 at 1:56 AM, Pascal Baerten <[email protected]> wrote: > hi Guil, > > The fastest conversion time for ds18b20 is 93,75ms with 9 bit resolution; I > don't know where you found 10ms... > > If you concern is to minimise duration on polling temperatures and if all > your ds18b20 are powered, you may issue a simultaneous temperature > conversion command, do something else for 750ms, then read the temperatures > as usual. > The simultaneous command instruct all temp sensors on the branch to start > the conversion. once the conversion is known (max duration is 750ms for > 12bit) to be finished, the next readings simply (should) read prepared data. > in you case, simultaneous conversion is triggered with: > owwrite -s 4444 /uncached/sw3/aux/simultaneous/temperature 1 > > not sure however that this behavior is working as expected when dealing with > a ds2409 in between. > > Pascal > >> > > 2011/1/23 Guil Barros <[email protected]> >> >> I am doing a number of reads with owget on individual DS18B20's and >> DS2438's and not quite getting the performance I expect: >> # time ./owfs/bin/ >> owget -s 4444 /uncached/sw3/aux/Hallway/temperature >> 18.9375 >> real 0m 0.38s >> user 0m 0.00s >> sys 0m 0.01s >> >> The actual convert_t from the datasheet should take only 10ms. What >> can I do to speed this up? (yes, that DS2409 port is already the >> active one). >> >> I have also noticed something similar for DS18B20 fasttemp reads which >> should take 95ms: >> # time ./owfs/bin/ >> owget -s 4444 /uncached/sw1/main/Attic/fasttemp >> -1 >> real 0m 0.84s >> user 0m 0.00s >> sys 0m 0.00s >> >> I assume this is at least partially overhead related to the owserver >> comms, is there a better way to handle multiple device access with the >> owshell commands? Anything I can do to speed things up otherwise? >> >> Thanks, >> -Guil >> >> >> ------------------------------------------------------------------------------ >> Special Offer-- Download ArcSight Logger for FREE (a $49 USD value)! >> Finally, a world-class log management solution at an even better >> price-free! >> Download using promo code Free_Logger_4_Dev2Dev. Offer expires >> February 28th, so secure your free ArcSight Logger TODAY! >> http://p.sf.net/sfu/arcsight-sfd2d >> _______________________________________________ >> Owfs-developers mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/owfs-developers > > > > -- > Pascal > www.brain4home.eu > to subscribe, send a mail to <[email protected]> > > ------------------------------------------------------------------------------ > Special Offer-- Download ArcSight Logger for FREE (a $49 USD value)! > Finally, a world-class log management solution at an even better price-free! > Download using promo code Free_Logger_4_Dev2Dev. Offer expires > February 28th, so secure your free ArcSight Logger TODAY! > http://p.sf.net/sfu/arcsight-sfd2d > _______________________________________________ > Owfs-developers mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/owfs-developers > > ------------------------------------------------------------------------------ Special Offer-- Download ArcSight Logger for FREE (a $49 USD value)! Finally, a world-class log management solution at an even better price-free! Download using promo code Free_Logger_4_Dev2Dev. Offer expires February 28th, so secure your free ArcSight Logger TODAY! http://p.sf.net/sfu/arcsight-sfd2d _______________________________________________ Owfs-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/owfs-developers
