111 lines
3.6 KiB
Groff
111 lines
3.6 KiB
Groff
.\" $NetBSD: bmx280thp.4,v 1.5 2022/12/03 01:04:42 brad Exp $
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.\"
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.\" Copyright (c) 2022 Brad Spencer <brad@anduin.eldar.org>
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.\"
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.\" Permission to use, copy, modify, and distribute this software for any
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.\" purpose with or without fee is hereby granted, provided that the above
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.\" copyright notice and this permission notice appear in all copies.
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.\"
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.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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.\"
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.Dd November 19, 2022
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.Dt BMX280THP 4
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.Os
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.Sh NAME
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.Nm bmx280thp
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.Nd Driver for Bosch BMP280/BME280 sensor chip via I2C bus
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.Sh SYNOPSIS
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.Cd "bmx280thp* at iic? addr 0x76"
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.Cd "bmx280thp* at iic? addr 0x77"
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.Cd "bmx280thp* at spi? slave 0"
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.Cd "bmx280thp* at spi? slave 1"
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.Sh DESCRIPTION
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The
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.Nm
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driver provides measurements from the BMP280 and BME280 temperature,
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humidity and barometric pressure sensors via the
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.Xr envsys 4
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framework.
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The
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.Nm
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.Ar addr
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argument selects the address at the
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.Xr iic 4
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bus and the
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.Nm
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.Ar slave
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argument selects which chip select will be used on the
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.Xr spi 4
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bus.
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The precision of the measurement which is related to the over
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sampling performed on the measurement can be changed through
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.Xr sysctl 8
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nodes.
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.Sh SYSCTL VARIABLES
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The following
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.Xr sysctl 3
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variables are provided:
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.Bl -tag -width indent
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.It Li hw.bmx280thp0.osrs_t
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.It Li hw.bmx280thp0.osrs_p
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.It Li hw.bmx280thp0.osrs_h
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These control oversampling of temperature, pressure and humidity.
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The valid values are 1, 2, 4, 8, and 16 times oversample.
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Humidity is only available if the chip is a BME280.
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.It Li hw.bmx280thp0.irr_samples
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IRR is a filter that can be used to reduce the noise in the
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measurement.
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The value values are 1 (or off), 2, 5, 11 and 22 samples
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to reach >= 75% of the step response.
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.It Li hw.bmx280thp0.waitfactor.t
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.It Li hw.bmx280thp0.waitfactor.p
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.It Li hw.bmx280thp0.waitfactor.h
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These control the wait multiplication factor for a measurement cycle.
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This factor is different for temperature, pressure and humidity and
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is based upon the values of osrs_t, osrs_p and osrs_h.
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If the chip does not return the correct measurements for a given
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over sampling then the wait factors can be adjusted to allow more
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time for the measurement to complete successfully.
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.It Li hw.bmx280thp0.debug
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.It Li hw.bmx280thp0.dump_calibration
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If the driver is compiled with
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.Dv BMX280_DEBUG ,
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these nodes will appear and can be used to set the debugging level and
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provide the calibration constants, upon refresh, that are stored in the
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chip.
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Since the constants are fixed, this is a boolean node and will
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reset back to false once one dump has been performed.
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.It Li hw.bmx280thp0.readattempts
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A status register tells the driver if the chip is busy with a measurement.
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This status register must be polled and readattempts is the number of times
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that this poll will be performed.
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The default is 25 which should be more than enough for most purposes.
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.El
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.Sh SEE ALSO
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.Xr envsys 4 ,
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.Xr iic 4 ,
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.Xr spi 4 ,
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.Xr envstat 8 ,
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.Xr sysctl 8
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.Sh HISTORY
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The
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.Nm
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driver first appeared in
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.Nx 10.0 .
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.Sh AUTHORS
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.An -nosplit
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The
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.Nm
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driver was written by
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.An Brad Spencer Aq Mt brad@anduin.eldar.org .
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.Sh BUGS
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The driver does not support the continuous read mode that the BMP280
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and BME280 has.
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