Hi all,
I have some trouble in reading temperature value from LM and AD sensors.
I use different i2c bus setup and with all of them i have different results.
As interface i use the followings one:
paralelle port ( ELV) one with pull ups of 3k3
i2c-tiny-usb from till harbaum and same pull up value
self made interface using atmega8 (TWI driver) and USB.
I manage having a connection with all of the interfaces, (i2cdetect works and
detect the different sensors), i can read the default register ( nl hyst, temp
min, temp max...), but once i read the actual temperature i have wierd results:
i used the same sensors with same cables for all of the interfaces :
PP : i measure 25°
tiny : i measure 27°
self made : i measure 30°
( my personnal thermometer is showing me 22°, i come always to the same value
when i redo the test)
I have those behaviours with all of my sensors and if i change the length of
the cables, the temperature also change ( actually it decreases with the
length).
So as i2c is a digital communication i can't understand why the temperature is
so sensitive to interfaces or cable length, as the bus has nothing to do with
the sensors ?.
I am stuk, and i don't see what i could do to find the problem.
has someone of you ever been experimenting such a strange behaviour?
what could be the cause of it ?
regards
vincent
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