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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 com-
     munications, 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 hu-
     midity 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 measure-
	     ments is successfully retrieved.

FDT CONFIGURATION
     On	an fdt(4) based	system,	a gpioths device node is typically defined di-
     rectly 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 config-
     urable 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	13.0		       December	8, 2019			  FreeBSD 13.0

NAME | SYNOPSIS | DESCRIPTION | HARDWARE | SYSCTL VARIABLES | FDT CONFIGURATION | HINTS CONFIGURATION | SEE ALSO | HISTORY

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