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.

Debian                                          December 8, 2019                                      GPIOTHS(4)