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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.