77 lines
2.2 KiB
Groff
77 lines
2.2 KiB
Groff
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.\" $NetBSD: aht20temp.4,v 1.1 2022/11/17 19:20:05 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 15, 2022
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.Dt AHT20TEMP 4
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.Os
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.Sh NAME
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.Nm aht20temp
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.Nd Driver for Guangzhou Aosong AHT20 sensor chip via I2C bus
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.Sh SYNOPSIS
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.Cd "aht20temp* at iic? addr 0x38"
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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 AHT20 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 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.aht20temp0.ignorecrc
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If set, the crc calculation for %RH and temperature will be ignored.
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.It Li hw.aht20temp0.debug
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If the driver is compiled with
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.Dv AHT20_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.aht20temp0.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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