testing tags...

On 7/12/05, vasile surducan <vsurducan@gmail.com> wrote:
> On 7/12/05, PicDude <picdude2@narwani.org> wrote:
> > I've implemented some 1-Wire code to read a DS18B20 sensor using a PIC,
> > using
> > parasite power.  Still in testing on a breadboard, it sits there all day
> > with
> > 2 sensors on the bus reading ~28 deg C.  But periodically, perhaps once
> > every
> > few hours, I get an odd value of "85", or "-21" once interpreted from the
> > DS18B20's format.  Seemingly important, this works out to B'10101010', and
> > even more important is that it passes the checksum test.
> >
> > I can now reproduce this by removing the positive power from the sensor.
> > And
> > it's always that magic "85".  Is there some significance to this, so that I
> >
> > can figure out how to determine it's bogus and not display 85?  >
> 
>  85 is the first value from the DS memory at power up. You are
> loosing your communication and the sensor is reset to it's initial
> value. Check if you have a correct time slot. 18B20 it's a very nice
> sensor. But be carefull, a wrong algorithm may change it's resolution
> by mistake and not by programming.
> 
> best regards,
> Vasile
>

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