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.