I was about to say basically what Michael said. If the DS18B20 is using parasitic power then you can’t do the read command or it can cause the T convert to fail.
Eric > On Oct 6, 2014, at 4:02 PM, Colin Reese <colin.re...@gmail.com> wrote: > > Hello all, > > Here is an interesting wrinkle that is not really owfs, but is > 1Wire-related, so I thought you might have some insight. > > I'm using OW on an arduino using the OneWire Library, and checking > repeatedly after issuing a T Convert command with a DS18B20 to determine > exactly when data is ready. This begins with instantiation of a OneWire > object, a reset, match/select, a T Convert, and then with a repeated > read command. When this returns 1, the data is ready. > > The question is this: if I recreate the object, is there any way to pick > up where I left off checking if the data is ready? This of course would > require a reset, which the device will ignore during conversion, but I > assume also a Match. Does this then make it impossible to resume the > data checking? Interestingly, reading scratchpad is successful even when > reading during what should be the conversion window. I assume this is > picking up stale data. > > The bottom line is that I have the possibility of multiple OneWire > buses, want to avoid global OneWire objects and creating memory space > for a whole bunch of them floating around. I think at the moment I'm > just going to have to enforce a space of time between convert and read > scratchpad, and then reinstantiate the object knowing that the data will > be ready to read by the time I do so, based on the resolution and the > datasheet. > > Suggestions welcome. > Colin > > > ------------------------------------------------------------------------------ > Slashdot TV. Videos for Nerds. Stuff that Matters. > http://pubads.g.doubleclick.net/gampad/clk?id=160591471&iu=/4140/ostg.clktrk > _______________________________________________ > Owfs-developers mailing list > Owfs-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/owfs-developers ------------------------------------------------------------------------------ Slashdot TV. Videos for Nerds. Stuff that Matters. http://pubads.g.doubleclick.net/gampad/clk?id=160591471&iu=/4140/ostg.clktrk _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
