Add a man page for the gpioths(4) driver.
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Ian Lepore
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share/man/man4/gpioths.4
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share/man/man4/gpioths.4
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.\"-
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.\" SPDX-License-Identifier: BSD-2-Clause
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.\"
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.\" Copyright (c) 2019 Ian Lepore <ian@freebsd.org>
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd December 8, 2019
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.Dt GPIOTHS 4
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.Os
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.Sh NAME
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.Nm gpioths
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.Nd driver for DHTxx and AM320x temperature and humidity sensors
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.Sh SYNOPSIS
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To compile this driver into the kernel,
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place the following line in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "device gpioths"
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.Ed
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.Pp
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Alternatively, to load the driver as a
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module at boot time, place the following line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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gpioths_load="YES"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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driver supports the DHTxx and AM320x family of
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temperature and humidity sensors.
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The driver automatically reads the values from the sensor
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once every 5 seconds, and makes the results available via
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.Xr sysctl 8
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variables.
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.Sh HARDWARE
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The
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.Nm
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driver provides support for the following devices:
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.Pp
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.Bl -column -compact -offset indent "XXXXXXXX" "XXXXXXXX"
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.It DHT11 Ta DHT12
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.It DHT21 Ta DHT22
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.It AM3201 Ta AM3202
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.El
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.Pp
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The supported devices are all similar to each other, varying
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primarily in accuracy and resolution.
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The devices require a single wire for data communications, using a
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custom protocol which is not compatible with Maxim's 1-wire(tm).
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The AM320x devices also support connection to an i2c bus,
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but this driver supports only the single-wire connection option.
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.Sh SYSCTL VARIABLES
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Sysctl variables are used to access the most recent temperature and
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humidity measurements.
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.Bl -tag -width indent
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.It Va dev.gpioths.<unit>.temp
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The current temperature in integer deciKelvins.
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Note that
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.Xr sysctl 8
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will convert those units to display in decimal degrees Celcius.
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.It Va dev.gpioths.<unit>.hum
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The current relative humidity, as an integer percentage.
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.It Va dev.gpioths.<unit>.fails
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The number of failed attempts to communicate with the sensor since
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the last good access.
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Cleared whenever a set of measurements is successfully retrieved.
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.El
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.Sh FDT CONFIGURATION
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On an
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.Xr fdt 4
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based system, a
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.Nm
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device node is typically defined directly under the root node, or under
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a simplebus node that represents a collection of devices on a board.
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.Pp
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The following properties are required in the
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.Nm
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device subnode:
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.Bl -tag -width indent
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.It Va compatible
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Must be "dht11".
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.It Va gpios
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A reference to the gpio device and pin for data communications.
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.El
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.Ss Example of adding a sensor with an overlay
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.Bd -unfilled -offset indent
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/dts-v1/;
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/plugin/;
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#include <dt-bindings/gpio/gpio.h>
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/ {
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compatible = "wand,imx6q-wandboard";
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};
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&{/} {
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dht0 {
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compatible = "dht11";
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gpios = <&gpio5 15 GPIO_ACTIVE_HIGH>;
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};
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};
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.Ed
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.Sh HINTS CONFIGURATION
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On a
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.Xr device.hints 5
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based system, such as
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.Li MIPS ,
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these values are configurable for
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.Nm :
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.Bl -tag -width indent
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.It Va hint.gpioths.<unit>.at
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The
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.Xr gpiobus 4
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instance the
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.Nm
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instance is attached to.
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.It Va hint.gpioths.pins
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A bitmask with a single bit set to indicate which gpio pin on the
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.Xr gpiobus 4
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to use for data communications.
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.El
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.Sh SEE ALSO
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.Xr fdt 4 ,
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.Xr gpiobus 4 ,
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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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.Fx 11.1 .
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