BMX280THP(4) FreeBSD 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.
Humidity 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
measurement. The value values are 1 (or off), 2, 5, 11 and 22
samples 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
readattempts is the number of times that this poll will be
performed. The default is 25 which should be more than enough
for most purposes.
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 <
[email protected]>.
BUGS
The driver does not support the continuous read mode that the BMP280 and
BME280 has.
FreeBSD 14.1-RELEASE-p8 November 19, 2022 FreeBSD 14.1-RELEASE-p8