am2315temp(4) - NetBSD Manual Pages

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AM2315TEMP(4)           NetBSD Kernel Interfaces Manual          AM2315TEMP(4)


NAME

     am2315temp -- Driver for Aosong AM2315 sensor chip via I2C bus


SYNOPSIS

     am2315temp* at iic? addr 0x5c


DESCRIPTION

     The am2315temp driver provides measurements from the AM2315 humidity/tem-
     perature sensors via the envsys(4) framework.  The am2315temp addr argu-
     ment selects the address at the iic(4) bus.  The AM2315 has limits on how
     often the measurements can be read.  Adjustments to the number of times
     to take reading before considering it valid, and the number of ticks to
     wait between readings can be changed through sysctl(8) nodes.

     There are other oddities about the AM2315 that should be mentioned.  The
     datasheet says that the device should read no more often then every 2
     seconds, further, it also implies that a measurement is not performed
     until the device is 1) awake 2) has been asked for a measurement.  From
     observation, it has been noted that it is possible to ask for measure-
     ments more often than every 2 seconds, and actually get something that
     looks to be valid.  It may, in fact, be valid, but it has also been noted
     that the measurements do not appear to change.  This implies that a mea-
     surement was done, and then returned time and time again.  It has also
     been noticed that if measurements are taken very close to every 2 sec-
     onds, that sometimes the device will return a I2C error on a read.  If
     this happens a lot, increase hw.am2315temp0.readticks a bit.


SYSCTL VARIABLES

     The following sysctl(3) variables are provided:

     hw.am2315temp0.readcount
             The number of times to take a reading before considering it
             valid.  This defaults to 2.

     hw.am2315temp0.readticks
             The number of ticks to wait in between readings.  The default is
             100.

     hw.am2315temp0.debug
             If the driver is compiled with AM2315_DEBUG, this node will
             appear and can be used to set the debugging level.


SEE ALSO

     envsys(4), iic(4), envstat(8), sysctl(8)


HISTORY

     The am2315temp driver first appeared in NetBSD 8.0.


AUTHORS

     The am2315temp driver was written by Brad Spencer
     <brad@anduin.eldar.org>.


BUGS

     The device does not appear to work with the gpioiic(4) bitbang con-
     troller.  When tried, reads would not error, but no data was returned.

NetBSD 10.0                    December 28, 2017                   NetBSD 10.0