98 lines
3.1 KiB
Groff
98 lines
3.1 KiB
Groff
.\" $NetBSD: sht4xtemp.4,v 1.2 2021/10/03 18:20:13 wiz Exp $
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.\"
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.\" Copyright (c) 2021 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 September 28, 2021
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.Dt SHT4XTEMP 4
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.Os
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.Sh NAME
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.Nm sht4xtemp
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.Nd Driver for Sensirion SHT40/SHT41/SHT45 sensor chip via I2C bus
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.Sh SYNOPSIS
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.Cd "sht4xtemp* at iic? addr 0x44"
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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 SHT40/SHT41/SHT45 humidity/temperature
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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.
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The resolution, heater controls and crc validity 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.sht4xtemp0.resolutions
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Lists the resolutions supported by the driver and chip.
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.It Li hw.sht4xtemp0.resolution
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Set the resolution, or number of bits, used for %RH and temperature.
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Use one of the strings listed in
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.Li hw.sht4xtemp.resolutions .
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.It Li hw.sht4xtemp0.ignorecrc
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If set, the crc calculation for %RH and temperature will be ignored.
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.It Li hw.sht4xtemp0.heateron
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Turn the heater on and off.
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Please note that the heater is turned on right
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before the measurement and runs for a pulse width of time.
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Then the measurement is taken and the heater is turned off.
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There is no way to keep the heater running with this chip.
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.It Li hw.sht4xtemp0.heaterstrength
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From 1 to 3, the amount of energy put into the heater.
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The higher the number, the more power used.
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.It Li hw.sht4xtemp0.heaterpulses
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Lists the valid heater pulses supported by the driver and chip.
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.It Li hw.sht4xtemp0.heaterpulse
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Set the heater pulse length.
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Use one of the strings listed in
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.Li hw.sht4xtemp.heaterpulses .
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.It Li hw.sht4xtemp0.debug
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If the driver is compiled with
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.Dv SI70XX_DEBUG ,
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this node will appear and can be used to set the debugging level.
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.It Li hw.sht4xtemp0.readattempts
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To read %RH or temperature the chip requires that the command be sent,
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then a delay must be observed before a read can be done to get the values
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back.
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The delays are documented in the datasheet for the chip.
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The driver will attempt to read back the values readattempts number of
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times.
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The default is 10 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 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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