DHT22 Sensor Implementation for ESP32

This document provides information about the DHT22 sensor implementation for ESP32 microcontrollers in this project.

Overview

The DHT22 (also known as AM2302) is a digital temperature and humidity sensor that provides high-precision temperature and humidity readings. This implementation allows you to easily integrate DHT22 sensors with your ESP32 projects using MicroPython.

Features

Temperature readings in Celsius or Fahrenheit
Humidity readings as percentage
Automatic detection of simulation vs. hardware mode
Error handling for sensor reading failures
Temperature unit conversion methods
Comprehensive metadata including sensor type and last readings
Configuration-based initialization
Separate configuration options for temperature and humidity components
Inherits functionality from both TemperatureSensor and HumiditySensor classes

Hardware Requirements

ESP32 microcontroller
DHT22/AM2302 temperature and humidity sensor
MicroPython firmware installed on the ESP32
Appropriate wiring:
- Connect VCC to 3.3V or 5V power supply
- Connect GND to ground
- Connect DATA to a GPIO pin (default is GPIO4)
- A 10K pull-up resistor between VCC and DATA is recommended

Software Dependencies

MicroPython with dht and machine modules
For simulation mode, only the standard Python libraries are required

Usage

Basic Usage

from src.esp_sensors.dht22 import DHT22Sensor

# Initialize the sensor
sensor = DHT22Sensor("living_room", 4)  # name, GPIO pin

# Read temperature
temperature = sensor.read()
print(f"Temperature: {temperature}°C")

# Read humidity
humidity = sensor.read_humidity()
print(f"Humidity: {humidity}%")

# Get temperature in Fahrenheit
fahrenheit = sensor.to_fahrenheit()
print(f"Temperature: {fahrenheit}°F")

Configuration-Based Usage

from src.esp_sensors.dht22 import DHT22Sensor

# Initialize using configuration
sensor_config = {
    "name": "bedroom",
    "pin": 5,
    "interval": 30,
    "temperature": {
        "name": "Bedroom Temperature",
        "unit": "F"
    },
    "humidity": {
        "name": "Bedroom Humidity"
    }
}

sensor = DHT22Sensor(sensor_config=sensor_config)

Advanced Usage

from src.esp_sensors.dht22 import DHT22Sensor
import time

# Initialize with custom parameters
sensor = DHT22Sensor(
  name="outdoor",
  pin=5,
  interval=30,  # Read every 30 seconds
  temperature_unit="F"  # Use Fahrenheit
)

# Continuous reading
try:
  while True:
    temp = sensor.read()
    humidity = sensor.read_humidity()

    # Get metadata
    metadata = sensor.get_metadata()

    print(f"Sensor: {metadata['name']}")
    print(f"Temperature: {temp}°F ({sensor.to_celsius()}°C)")
    print(f"Humidity: {humidity}%")

    time.sleep(metadata['interval'])
except KeyboardInterrupt:
  print("Monitoring stopped")

API Reference

Class: DHT22Sensor

Extends both the TemperatureSensor and HumiditySensor classes to provide DHT22-specific functionality for reading both temperature and humidity from a single sensor.

Constructor

DHT22Sensor(
    name: str = None,
    pin: int = None,
    interval: int = None,
    temperature_unit: str = None,
    sensor_config: Dict[str, Any] = None
)

name: A string identifier for the sensor (if None, loaded from config)
pin: The GPIO pin number the sensor is connected to (if None, loaded from config)
interval: Reading interval in seconds (if None, loaded from config)
temperature_unit: Temperature unit, either "C" for Celsius or "F" for Fahrenheit (if None, loaded from config)
sensor_config: Sensor configuration dictionary (if provided, used instead of loading from file)

Methods

read(): Reads the current temperature and updates humidity
read_temperature(): Reads the current temperature (same as read())
read_humidity(): Returns the current humidity reading
to_fahrenheit(): Converts the last reading to Fahrenheit if it was in Celsius
to_celsius(): Converts the last reading to Celsius if it was in Fahrenheit
get_metadata(): Returns a dictionary with sensor information including temperature unit and humidity
apply_parameters(): Internal method to apply configuration parameters

Example

See the examples/dht22_example.py file for a complete example of how to use the DHT22 sensor with an ESP32.

Troubleshooting

No readings or errors: Check your wiring and ensure the DHT22 is properly connected
Inconsistent readings: Make sure you have a pull-up resistor between VCC and DATA
ImportError: Ensure you're running on MicroPython with the required modules
ValueError: Check that you're using a valid temperature unit ("C" or "F")

License

This implementation is provided under the same license as the main project.

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