dht11_gpio

Rust library for interfacing with the DHT11 temperature & humidity sensor.

crates.io

Wiring

Credit goes to this guide on how to properly wire up the sensor - circuitbasics.com

IMPORTANT!

Connect the Vcc (+) to the 3.3v Power, NOT the 5v Power pin, because the signal would exceed the standard 3.3v of power the input pins take by using a pull-up resistor.

DHT11 Pinout

3 pin

4 pin

note: The resistor is a 10K Ohm pull up resistor` connected between the Vcc and signal lines.

Usage

Installation

Add the crate to your project:

cargo add dht11_gpio

or add to Cargo.toml manually:

[dependencies]
dht11_gpio = "0.1.0"

check for the latest version on crates.io/dht11_gpio

Basic usage

use dht11_gpio::{DHT11Controller, Sensor};

fn main() {
    const DHT11_PIN: u8 = 4;

    let mut sensor = DHT11Controller::new(DHT11_PIN).unwrap();

    let result = sensor.read_sensor_data();
    match result {
        Ok(data) => {
            println!("temperature: {} °C", data.temperature);
            println!("humidity: {} %", data.humidity);
        }
        Err(err) => {
            println!("error: {}", err);
        }
    }
}

note: the sensor returns the temperature in celcius

Possible errors

The DHT11Controller::read_sensor_data() method can fail to retrieve the correct sensor data if:

1. Bit Count Mismatch (DHT11Error::MissingData):

   • Description: This error occurs when the number of bits received from the DHT11 sensor is not the expected 40 bits (4 bytes of data + 1 byte checksum).
   • Possible Reasons: It may happen due to communication issues or incorrect data reception from the sensor.

2. Invalid Checksum (DHT11Error::InvalidChecksum):

   • Description: This error occurs when the calculated checksum (sum of the first 4 bytes) does not match the validation checksum (last byte) received from the DHT11 sensor.
   • Possible Reasons: It indicates a potential corruption or error in the received data. The sensor uses the checksum to validate the integrity of the transmitted information.

The implimentation of read_sensor_data() is not perfect as it is implemented with a fixed 200ms timeout for receiving the data from the sensor, this sometimes leads to getting the MissingData error.

References

• wiring guide - circuitbasics.com
• DHT11 datasheet
• GPIO pinout
• rppal - crate used to interface with the GPIO pins of the raspberry pi through rust