dht-embedded

dht-embedded is a Rust crate that reads temperature and humidity data from the DHT11 and DHT22 sensors.

Prerequisites

• You've connected the DHT sensor to your device (such as a Raspberry Pi or ESP32) using a GPIO pin.

Usage

Add the following to your Cargo.toml:

toml [dependencies] dht-embedded = "=0.1.0-alpha.1"

Note that this crate currently tracks the 1.0.0 alpha releases of embedded-hal, so things can change & break often, and your platform's embedded-hal implementation may not have trait impls for 1.0.0 alphas at all, let alone the current one this crate supports.

You will need to use an embedded-hal implementation for your hardware. Here's a simple one using linux-embedded-hal and `gpio-cdev, which could be used on a Rasperry Pi.

```rust,norun,ignore use dhtembedded::{Dht22, DhtSensor, NoopInterruptControl}; use gpiocdev::{Chip, LineRequestFlags}; use linuxembedded_hal::{CdevPin, Delay}; use std::{thread::sleep, time::Duration};

fn main() -> anyhow::Result<()> { let mut gpiochip = Chip::new("/dev/gpiochip0")?; let line = gpiochip.get_line(17)?; let handle = line.request(LineRequestFlags::INPUT | LineRequestFlags::OUTPUT, 1, "dht-sensor")?; let pin = CdevPin::new(handle)?; let mut sensor = Dht22::new(NoopInterruptControl, Delay, pin);

loop {
    match sensor.read() {
        Ok(reading) => println!("{}°C, {}% RH", reading.temperature(), reading.humidity()),
        Err(e) => eprintln!("Error: {}", e),
    }

    sleep(Duration::from_millis(2100));
}

} ```

(To be fair, the Linux kernel includes a driver for DHT sensors, and honestly it's probably better to use that driver, since kernel space can disable interrupts and get much more precise timing than we can.)

Why

A search of crates.io might yield several different implementations of this driver. I wrote this because none of the others worked for me, and, upon examination of their code, I found they used a completely different protocols for reading from the sensor, protocols I couldn't find documented anywhere as what's supposed to work. This crate implements one of the simpler protocols that doesn't require access to a system clock, but still seems to work most of the time.