On Tue, 19 Sep 2017 08:42:21 +0200 "H. Nikolaus Schaller" <[email protected]> wrote:
> Hi, > > > Am 19.09.2017 um 08:01 schrieb Andreas Kemnade <[email protected]>: > > > > Hi, > > > > On Sat, 16 Sep 2017 21:57:32 +0200 > > "H. Nikolaus Schaller" <[email protected]> wrote: > > > >> Hi, > >> since we a re a tinkerphones community, I just had > >> some fun with the GTA04A5 I want to share :) > >> > >> Maybe you know that there is a BME280 inside. It > >> is a combined barometer, thermometer, hygrometer > >> sensor chip. > >> > >> And it has full Letux kernel support so that it > >> works out of the box. > >> > > Well, to produce nice input there still needs to be some logic, > > Probably some power management logic. like suspend for some minutes to let > > the > > gta04 cool down and read then the sensor directly after suspend. > > That is easy: > > ./measure-suspend 300; cat > /sys/bus/iio/devices/iio:device5/in_humidityrelative_input > > Or integrate it into a new script that does similar things as > ./measure-suspend > for suspend + wakeup by RTC. > > > > > So the question is: does the hygrometer produce sane output when the gta04 > > case > > is closed? > > Yes, that would be nice if someone could find out. > > > > >> It was simple to do some readout: > >> > >> cat /sys/bus/iio/devices/iio:device5/in_humidityrelative_input > >> > >> Here is the full sequence when breathing upon > >> the sensor (of a board not installed in the case): > >> > >> root@letux:~# while true; do cat > >> /sys/bus/iio/devices/iio:device5/in_humidityrelative_input; sleep 1; done > >> 35.765625000 > > root@letux:/sys/bus/iio/devices/iio:device1# cat in_temp_input > > 39100 > > root@letux:/sys/bus/iio/devices/iio:device1# cat in_humidityrelative_input > > 78.563476562 > > > > Hmm, that does not make sense. 78% at 39 C. It was not in > > my pocket. It is in a train. So why it is so humid? > > Hm. Maybe the sensor needs calibration? More likely it is too much > influenced by the device temperature. > > Maybe printing temperature and humidity in a loop right after booting > shows some drift/correlation? > That should clearly be monitored. Of course I measure some innner device temperature and not outdoor temperature but I do not understand why a high device temperature would create a wrong humidity. Higher temperature -> air can store more vapour -> RH will go down. If I measure something I like to understand what I am actually measuring and how it is influenced. Regards, Andreas
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