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 <p4tr...@o2.pl>: > > > 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 Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
