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 Celcius.

     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.