README.md

embedded-dht-rs

embedded-dht-rs is a Rust library designed to simplify interfacing with DHT sensors in embedded systems.

This library is #![no_std] and depends only on embedded_hal, making it versatile and compatible with virtually any microcontroller.

Support for DHT11, DHT20, and DHT22 Sensors: All three sensors are fully implemented and ready for use.

The library has been tested with the ESP32-WROOM, and a detailed example is provided below to help you get started.

Getting Started

Tutorials

Here are some general tutorials that provide brief introductions to embedded programming:

• Part 1 (Introduction) - Introduction to Embedded Systems with Rust: A Beginner's Guide Using ESP32
• Part 2 (LED + Button) - Building a Simple LED and Button Interface with Rust on ESP32
• Part 3 (DHT11 Library) - Building a Rust library for DHT11 sensor

Install

To include the dht11 feature:

cargo add embedded-dht-rs --features "dht11"

To include all features (dht11, dht20, and dht22):

cargo add embedded-dht-rs --features "dht11,dht20,dht22"

Example - ESP32

You can find the full example in the examples folder.

#![no_std]
#![no_main]

use embedded_dht_rs::{dht11::Dht11, dht20::Dht20, dht22::Dht22};
use esp_backtrace as _;
use esp_hal::{
    clock::ClockControl, delay::Delay, gpio::{Io, Level, OutputOpenDrain, Pull}, i2c::I2C, peripherals::Peripherals, prelude::*, system::SystemControl
};
use fugit::HertzU32;

#[entry]
fn main() -> ! {
    let peripherals = Peripherals::take();
    let system = SystemControl::new(peripherals.SYSTEM);
    let clocks = ClockControl::boot_defaults(system.clock_control).freeze();
    let io = Io::new(peripherals.GPIO, peripherals.IO_MUX);

    esp_println::logger::init_logger_from_env();

    let delay = Delay::new(&clocks);

    let od_for_dht11 = OutputOpenDrain::new(io.pins.gpio4, Level::High, Pull::None);
    let od_for_dht22 = OutputOpenDrain::new(io.pins.gpio5, Level::High, Pull::None);
    let i2c_for_dht20 = I2C::new(
        peripherals.I2C0, 
        io.pins.gpio21,
        io.pins.gpio22, 
        HertzU32::kHz(400),
        &clocks
    );

    let mut dht11 = Dht11::new(od_for_dht11, delay);
    let mut dht22 = Dht22::new(od_for_dht22, delay);
    let mut dht20 = Dht20::new(i2c_for_dht20, delay);

    loop {
        delay.delay(5000.millis());

        match dht11.read() {
            Ok(sensor_reading) => log::info!(
                "DHT 11 Sensor - Temperature: {} °C, humidity: {} %",
                sensor_reading.temperature,
                sensor_reading.humidity
            ),
            Err(error) => log::error!("An error occurred while trying to read sensor: {:?}", error),
        }

        match dht22.read() {
            Ok(sensor_reading) => log::info!(
                "DHT 22 Sensor - Temperature: {} °C, humidity: {} %",
                sensor_reading.temperature,
                sensor_reading.humidity
            ),
            Err(error) => log::error!("An error occurred while trying to read sensor: {:?}", error),
        }

        match dht20.read() {
            Ok(sensor_reading) => log::info!(
                "DHT 20 Sensor - Temperature: {} °C, humidity: {} %",
                sensor_reading.temperature,
                sensor_reading.humidity
            ),
            Err(error) => log::error!("An error occurred while trying to read sensor: {:?}", error),
        }

        log::info!("-----");
    }
}

Implementation Specification

We have gathered all the information you need to understand in order to implement a library like this. Additionally, we’ve included a few comments in the code for those curious about the details, based on the following specification.

The DHT20 differs from the DHT11 and DHT22 because it uses the I2C communication protocol, while both the DHT11 and DHT22 rely on a single-wire signal for data transmission.

• DHT11 and DHT22 Documentation
• DHT20 Documentation

Comparison of DHT11, DHT20, and DHT22 40-Bit Data Formats

Feature	DHT11	DHT20	DHT22
Data Structure	- Byte 1: Humidity Int - Byte 2: Humidity Dec (0) - Byte 3: Temp Int - Byte 4: Temp Dec (0) - Byte 5: Checksum	- Byte 1: Humidity High - Byte 2: Humidity Low - Byte 3: Temp High - Byte 4: Temp Low - Byte 5: CRC	- Byte 1: Humidity High - Byte 2: Humidity Low - Byte 3: Temp High - Byte 4: Temp Low - Byte 5: Checksum
Precision	Integer only	Higher precision with decimals	Higher precision with decimals
Example Temp	25°C	25.6°C	25.6°C
Example Humidity	60%	60.5%	60.5%
Example Data Bytes	60, 0, 25, 0, 85	2, 93, 1, 0, CRC	2, 93, 1, 0, 96
Range	Temp: 0–50°C Hum: 20–90%	Temp: -40–80°C Hum: 10–90%	Temp: -40–80°C Hum: 0–100%

Example Schematic

Click to zoom	Click to zoom