gpioths —
driver
for DHTxx and AM320x temperature and humidity sensors
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):
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.
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 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.
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.
/dts-v1/;
/plugin/;
#include <dt-bindings/gpio/gpio.h>
/ {
compatible = "wand,imx6q-wandboard";
};
&{/} {
dht0 {
compatible = "dht11";
gpios = <&gpio5 15 GPIO_ACTIVE_HIGH>;
};
};
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.
fdt(4),
gpiobus(4),
sysctl(8)
The
gpioths driver first appeared in
FreeBSD 11.1.