GPIOTHS(4)             FreeBSD Kernel Interfaces Manual             GPIOTHS(4)

NAME
     gpioths - driver for DHTxx and AM320x temperature and humidity sensors

SYNOPSIS
     To compile this driver into the kernel, place the following line in your
     kernel configuration file:

           device gpioths

     Alternatively, to load the driver as a module at boot time, place the
     following line in loader.conf(5):

           gpioths_load="YES"

DESCRIPTION
     The gpioths driver supports the DHTxx and AM320x family of temperature
     and humidity sensors.  The driver automatically reads the values from the
     sensor once every 5 seconds, and makes the results available via
     sysctl(8) variables.

HARDWARE
     The gpioths driver provides support for the following devices:

           DHT11       DHT12
           DHT21       DHT22
           AM3201      AM3202

     The supported devices are all similar to each other, varying primarily in
     accuracy and resolution.  The devices require a single wire for data
     communications, using a custom protocol which is not compatible with
     Maxim's 1-wire(tm).  The AM320x devices also support connection to an i2c
     bus, but this driver supports only the single-wire connection option.

SYSCTL VARIABLES
     Sysctl variables are used to access the most recent temperature and
     humidity measurements.

     dev.gpioths.<unit>.temp
             The current temperature in integer deciKelvins.  Note that
             sysctl(8) will convert those units to display in decimal degrees
             Celsius.

     dev.gpioths.<unit>.hum
             The current relative humidity, as an integer percentage.

     dev.gpioths.<unit>.fails
             The number of failed attempts to communicate with the sensor
             since the last good access.  Cleared whenever a set of
             measurements is successfully retrieved.

FDT CONFIGURATION
     On an fdt(4) based system, a gpioths device node is typically defined
     directly under the root node, or under a simplebus node that represents a
     collection of devices on a board.

     The following properties are required in the gpioths device subnode:

     compatible
             Must be "dht11".

     gpios   A reference to the gpio device and pin for data communications.

   Example of adding a sensor with an overlay
           /dts-v1/;
           /plugin/;
           #include <dt-bindings/gpio/gpio.h>

           / {
               compatible = "wand,imx6q-wandboard";
           };

           &{/} {
               dht0 {
                   compatible = "dht11";
                   gpios = <&gpio5 15 GPIO_ACTIVE_HIGH>;
               };
           };

HINTS CONFIGURATION
     On a device.hints(5) based system, such as MIPS, these values are
     configurable for gpioths:

     hint.gpioths.<unit>.at
             The gpiobus(4) instance the gpioths instance is attached to.

     hint.gpioths.pins
             A bitmask with a single bit set to indicate which gpio pin on the
             gpiobus(4) to use for data communications.

SEE ALSO
     fdt(4), gpiobus(4), sysctl(8)

HISTORY
     The gpioths driver first appeared in FreeBSD 11.1.

FreeBSD 13.1-RELEASE-p6        December 8, 2019        FreeBSD 13.1-RELEASE-p6