die: C2 I belive too that owfs is doing this properly, but somthing goes wrong when there is an hub connected between master and slave.
/Thomas Mark Richards skrev: > Thomas Berg wrote: >> Hi again, >> >> Yes I can both read and set temp hi and low. I´ve read somwhere on the >> internet that 85C is an error you get if you do the reading too fast >> from the 1820 after you have sent the request. If I understood ow_1820.c > After issuing the conversion the buss must stay high on a parasitic > network and you must wait at least the conversion time of the device > and then read the temperature register. > > OWFS must of course be doing this properly, otherwise there would be a > ton of messages from users with temperature devices that are failing. > > Worth considering might be the report that certain batches of > DS18x20's (the "B7" rev of the POR circuitry) had a problem with their > power on reset circuitry fixed in the subsequent "C2" revision whereby > they would remain in a "test" mode and would issue an error like this > after a convert. The nominal POR value of the temperature register is > 85.000 degrees C. According to my reading a power cycle of the chip > will usually fix the issue, but you can also send a reset, skip match > rom, followed by a 0x64 command, which issues a power ON reset to the > chip which restores the chip's trim values and resolves the problem. > > I am using this for all my DS18x20 code as a precaution. > > I am having trouble posting to the OWFS list as it's rather fussy > about certain mailserver capabilities so this message is being sent > directly to Thomas and a cc to the list. > > /mark > > > ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
