Crate dht22_driver

DHT22

No-std, no-dependency, platform-agnostic driver for the dht22 sensor

Features

• critical-section is used by default to prevent interrupts from messing with the timing-based data transfer protocol of the sensor. While it is recommended to use if possible, the driver may still work reliably if interrupts are disabled another way. Otherwise the chance for additional spurious invalid reads due to timing mismatches may be acceptable, as spurious failurs should be handled anyway.
• std provides an implementation of std::error::Error for the DhtError, allowing more ergonomic error handling. When error_in_core is stabelized this feature may be deprecated and possibly removed.

Example usage

A specific example for the esp32c3mini1 board is available in the examples folder. This example can also be run using wokwi (see the accompanying justfile for further details how to run it).

An example usage without any platform specific implementation is shown below.

use dht22_driver::{IOPin, MicroTimer, Microseconds, Dht22};
// Newtype over device specific GPIO pin type
struct Pin;
#[derive(Debug)]
struct SomeMCUSpecificError;
impl IOPin for Pin
{
    type DeviceError = SomeMCUSpecificError;
    fn set_low(&mut self) -> Result<(), Self::DeviceError> {
        todo!()
    }
    fn set_high(&mut self) -> Result<(), Self::DeviceError> {
        todo!()
    }
    fn is_low(&self) -> bool {
        todo!()
    }
    fn is_high(&self) -> bool {
        todo!()
    }
}
// Newtype over device specific clock/timer
struct DeviceTimer;
impl MicroTimer for DeviceTimer {
    fn now(&self) -> Microseconds {
        Microseconds(
            todo!()
        )
    }
}
fn main() -> Result<(), SomeMCUSpecificError> {
    let mut pin = Pin;
    pin.set_high()?;
    let timer = DeviceTimer;
    let mut sensor = Dht22::new(pin, timer);
    loop {
        std::thread::sleep(std::time::Duration::from_secs(2));
        if let Ok(reading) = sensor.read() {
            println!("Humidity: {:?}, Temperature: {:?}", reading.humidity, reading.temperature);    
        }
    }
}

Structs

• Dht22
  Represents a DHT22 sensor connected to a pin.
• Microseconds
  Represents a number of microseconds. Simple Newtype to attach meaning to the contained primitive. The std::duration::Duration which could also be used here is a much larger type in order to accomodate much bigger time spans, which may impact performance, code size and stack usage.
• SensorReading
  A valid reading from the DHT22 sensor

Enums

• DhtError

Traits

• IOPin
  Represents a GPIO pin capable of reading and setting the voltage level
• MicroTimer
  Represents a timer with microsecond resolution