GPIOTHS(4)

✨ NAME ✨

okay so welcome to the GPIOTHS(4) page from the Kernel Interfaces Manual — this is the tea on gpioths, the driver for DHTxx and AM320x temperature and humidity sensors. 💖

🎀 SYNOPSIS 🎀

bestie, if you want this compiled into the kernel, drop this line into your kernel configuration file:

device gpioths

or, if you’d rather load the driver as a module at boot time, put this 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 these devices, no cap:

• 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>.temperature — the current temperature in integer deciKelvins. Note that sysctl(8) will convert those units to display in decimal degrees Celsius.
• dev.gpioths.<unit>.humidity — 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. periodt. 🫶

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💌 cute little sign-off, bestie: footer source/version is Debian, the date is December 8, 2019, and the page is GPIOTHS(4). slay. 💅