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I wired 10 DS18B20 to the raspberry pi, in the normal powered mode. I am using the Raspbian's built in w1-gpio and w1-therm. I am able to read all the 10 sensor values.

Problem is, after (seemingly random) few hours of continuous pooling, I observe that all my sensors drop precision to 9 bit and only show temperatures with 0.5 Celsius precision. I can revert the sensors back to the default precision by interrupting their power for a short while.

Anyone knows what might cause this? I started to introduce little changes, to detect the cause, but the long time required for this to happen makes the process tedious.

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  • i know its been a while, but just in case this is still an issue (with the newest kernel), can you post the exact values for each slaves "w1_slave" file, e.g. via "cat /sys/bus/w1/devices/28-*/w1_slave" – x29a Apr 11 '16 at 18:13
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Maybe it's a short? Seems like a similar problem...

  • Thanks! Checked, it's not a short. Also there is no mechanical movement during the transition between precisions. I am thinking maybe this guy had similar problem and was actually solved by resetting the DS18B20 during the wire debbugging. – sanyi Oct 27 '14 at 15:03

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