On 7/12/05, PicDude 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 -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist