A couple of the sensors sometimes report the temperature -20.5.. ie the first two data bytes in the w1_slave file are 98 FE.
This reading is clearly wrong, since this result appears in a time stream of readings between 18 and 22 degrees C.
Code: Select all
98 fe ff ff 7f ff ff ff 1c : crc=1c YES 98 fe ff ff 7f ff ff ff 1c t=-22500
I know the device/driver will report 85C upon reset, but I have not found any information as to why -22.5C might be returned. The driver is reporting that the CRC is valid and the probe config byte reads correctly as 7f indicating the max resolution of 1/16 of a degree.
Has anyone else got the same issue.
Is it a hardware(probe) fault? in which case why do two probes both report exactly the same wrong reading, does -22.5 have a meaning which the driver should trap / report.
Each installation that shows the problem uses a single probe on the 1-wire bus powered from the Pi 3.3V pin. The data line has a single 4.7k pull-up resistor connected to the 3.3V line. Oh and GND of course.