bmx280thp(4) - NetBSD Manual Pages

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BMX280THP(4)            NetBSD Kernel Interfaces Manual           BMX280THP(4)


NAME

     bmx280thp -- Driver for Bosch BMP280/BME280 sensor chip via I2C bus


SYNOPSIS

     bmx280thp* at iic? addr 0x76
     bmx280thp* at iic? addr 0x77

     bmx280thp* at spi? slave 0
     bmx280thp* at spi? slave 1


DESCRIPTION

     The bmx280thp driver provides measurements from the BMP280 and BME280
     temperature, humidity and barometric pressure sensors via the envsys(4)
     framework.  The bmx280thp addr argument selects the address at the iic(4)
     bus and the bmx280thp slave argument selects which chip select will be
     used on the spi(4) bus.  The precision of the measurement which is
     related to the over sampling performed on the measurement can be changed
     through sysctl(8) nodes.


SYSCTL VARIABLES

     The following sysctl(3) variables are provided:

     hw.bmx280thp0.osrs_t

     hw.bmx280thp0.osrs_p

     hw.bmx280thp0.osrs_h
             These control oversampling of temperature, pressure and humidity.
             The valid values are 1, 2, 4, 8, and 16 times oversample.  Humid-
             ity is only available if the chip is a BME280.

     hw.bmx280thp0.irr_samples
             IRR is a filter that can be used to reduce the noise in the mea-
             surement.  The value values are 1 (or off), 2, 5, 11 and 22 sam-
             ples to reach >= 75% of the step response.

     hw.bmx280thp0.waitfactor.t

     hw.bmx280thp0.waitfactor.p

     hw.bmx280thp0.waitfactor.h
             These control the wait multiplication factor for a measurement
             cycle.  This factor is different for temperature, pressure and
             humidity and is based upon the values of osrs_t, osrs_p and
             osrs_h.  If the chip does not return the correct measurements for
             a given over sampling then the wait factors can be adjusted to
             allow more time for the measurement to complete successfully.

     hw.bmx280thp0.debug

     hw.bmx280thp0.dump_calibration
             If the driver is compiled with BMX280_DEBUG, these nodes will
             appear and can be used to set the debugging level and provide the
             calibration constants, upon refresh, that are stored in the chip.
             Since the constants are fixed, this is a boolean node and will
             reset back to false once one dump has been performed.

     hw.bmx280thp0.readattempts
             A status register tells the driver if the chip is busy with a
             measurement.  This status register must be polled and readat-
             tempts is the number of times that this poll will be performed.
             The default is 25 which should be more than enough for most pur-
             poses.


SEE ALSO

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


HISTORY

     The bmx280thp driver first appeared in NetBSD 10.0.


AUTHORS

     The bmx280thp driver was written by Brad Spencer <brad@anduin.eldar.org>.


BUGS

     The driver does not support the continuous read mode that the BMP280 and
     BME280 has.

NetBSD 10.0                    November 19, 2022                   NetBSD 10.0