1.\"- 2.\" SPDX-License-Identifier: BSD-2-Clause 3.\" 4.\" Copyright (c) 2019 Ian Lepore <ian@freebsd.org> 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.Dd December 8, 2019 28.Dt GPIOTHS 4 29.Os 30.Sh NAME 31.Nm gpioths 32.Nd driver for DHTxx and AM320x temperature and humidity sensors 33.Sh SYNOPSIS 34To compile this driver into the kernel, 35place the following line in your 36kernel configuration file: 37.Bd -ragged -offset indent 38.Cd "device gpioths" 39.Ed 40.Pp 41Alternatively, to load the driver as a 42module at boot time, place the following line in 43.Xr loader.conf 5 : 44.Bd -literal -offset indent 45gpioths_load="YES" 46.Ed 47.Sh DESCRIPTION 48The 49.Nm 50driver supports the DHTxx and AM320x family of 51temperature and humidity sensors. 52The driver automatically reads the values from the sensor 53once every 5 seconds, and makes the results available via 54.Xr sysctl 8 55variables. 56.Sh HARDWARE 57The 58.Nm 59driver provides support for the following devices: 60.Pp 61.Bl -column -compact -offset indent "XXXXXXXX" "XXXXXXXX" 62.It DHT11 Ta DHT12 63.It DHT21 Ta DHT22 64.It AM3201 Ta AM3202 65.El 66.Pp 67The supported devices are all similar to each other, varying 68primarily in accuracy and resolution. 69The devices require a single wire for data communications, using a 70custom protocol which is not compatible with Maxim's 1-wire(tm). 71The AM320x devices also support connection to an i2c bus, 72but this driver supports only the single-wire connection option. 73.Sh SYSCTL VARIABLES 74Sysctl variables are used to access the most recent temperature and 75humidity measurements. 76.Bl -tag -width indent 77.It Va dev.gpioths.<unit>.temperature 78The current temperature in integer deciKelvins. 79Note that 80.Xr sysctl 8 81will convert those units to display in decimal degrees Celsius. 82.It Va dev.gpioths.<unit>.humidity 83The current relative humidity, as an integer percentage. 84.It Va dev.gpioths.<unit>.fails 85The number of failed attempts to communicate with the sensor since 86the last good access. 87Cleared whenever a set of measurements is successfully retrieved. 88.El 89.Sh FDT CONFIGURATION 90On an 91.Xr fdt 4 92based system, a 93.Nm 94device node is typically defined directly under the root node, or under 95a simplebus node that represents a collection of devices on a board. 96.Pp 97The following properties are required in the 98.Nm 99device subnode: 100.Bl -tag -width indent 101.It Va compatible 102Must be "dht11". 103.It Va gpios 104A reference to the gpio device and pin for data communications. 105.El 106.Ss Example of adding a sensor with an overlay 107.Bd -unfilled -offset indent 108/dts-v1/; 109/plugin/; 110#include <dt-bindings/gpio/gpio.h> 111 112/ { 113 compatible = "wand,imx6q-wandboard"; 114}; 115 116&{/} { 117 dht0 { 118 compatible = "dht11"; 119 gpios = <&gpio5 15 GPIO_ACTIVE_HIGH>; 120 }; 121}; 122.Ed 123.Sh HINTS CONFIGURATION 124On a 125.Xr device.hints 5 126based system, such as 127.Li MIPS , 128these values are configurable for 129.Nm : 130.Bl -tag -width indent 131.It Va hint.gpioths.<unit>.at 132The 133.Xr gpiobus 4 134instance the 135.Nm 136instance is attached to. 137.It Va hint.gpioths.pins 138A bitmask with a single bit set to indicate which gpio pin on the 139.Xr gpiobus 4 140to use for data communications. 141.El 142.Sh SEE ALSO 143.Xr fdt 4 , 144.Xr gpiobus 4 , 145.Xr sysctl 8 146.Sh HISTORY 147The 148.Nm 149driver first appeared in 150.Fx 11.1 . 151