How to Use Adafruit HTS221: Examples, Pinouts, and Specs

The Adafruit HTS221 (Part ID: 4535) is a digital humidity and temperature sensor designed for precise environmental monitoring. Manufactured by Adafruit, this sensor combines high accuracy with ease of use, thanks to its I2C communication interface. The HTS221 is ideal for applications such as weather stations, HVAC systems, IoT devices, and other projects requiring reliable humidity and temperature measurements.

• Weather monitoring systems
• HVAC (Heating, Ventilation, and Air Conditioning) control
• IoT environmental sensing
• Industrial and home automation
• Data logging and scientific experiments

The Adafruit HTS221 is a compact and efficient sensor with the following key specifications:

The Adafruit HTS221 breakout board includes the following pins:

To use the Adafruit HTS221 with a microcontroller (e.g., Arduino UNO), follow these steps:

1. Connect the VIN pin to the 3.3V or 5V power supply of the microcontroller.
2. Connect the GND pin to the ground of the microcontroller.
3. Connect the SCL pin to the I2C clock pin (A5 on Arduino UNO).
4. Connect the SDA pin to the I2C data pin (A4 on Arduino UNO).
5. Leave the CS pin unconnected for I2C communication.
6. Optionally, connect the INT pin to a GPIO pin if you plan to use interrupts.

Below is an example of how to use the Adafruit HTS221 with an Arduino UNO. This code uses the Adafruit HTS221 library, which can be installed via the Arduino Library Manager.

#include <Wire.h>
#include <Adafruit_HTS221.h>

// Create an instance of the HTS221 sensor
Adafruit_HTS221 hts;

void setup() {
  Serial.begin(9600);
  while (!Serial) {
    delay(10); // Wait for Serial Monitor to open
  }

  // Initialize the HTS221 sensor
  if (!hts.begin_I2C()) {
    Serial.println("Failed to find HTS221 sensor! Check wiring.");
    while (1) {
      delay(10); // Halt execution if sensor is not found
    }
  }

  Serial.println("HTS221 sensor initialized successfully!");
}

void loop() {
  // Read humidity and temperature values
  float humidity = hts.readHumidity();
  float temperature = hts.readTemperature();

  // Print the values to the Serial Monitor
  Serial.print("Humidity: ");
  Serial.print(humidity);
  Serial.println(" %RH");

  Serial.print("Temperature: ");
  Serial.print(temperature);
  Serial.println(" °C");

  delay(1000); // Wait 1 second before the next reading
}

• Ensure the I2C pull-up resistors are present on the SDA and SCL lines. Most breakout boards include these resistors by default.
• The HTS221 operates at a maximum voltage of 3.6V. If using a 5V microcontroller, ensure the breakout board includes a voltage regulator and level shifters (Adafruit's breakout board does).
• Avoid exposing the sensor to extreme conditions (e.g., condensation or high humidity for prolonged periods) to maintain accuracy.

1. Sensor not detected:

   • Ensure the I2C connections (SDA, SCL) are correct and secure.
   • Verify the I2C address (default is 0x5F). Use an I2C scanner sketch to confirm.
   • Check the power supply voltage (must be between 1.7V and 3.6V).

2. Incorrect or fluctuating readings:

   • Ensure the sensor is not exposed to rapid temperature or humidity changes.
   • Avoid placing the sensor near heat sources or in direct sunlight.
   • Calibrate the sensor if necessary (refer to the Adafruit HTS221 library documentation).

3. Interrupt pin not working:

   • Verify the interrupt configuration in your code.
   • Ensure the INT pin is connected to a GPIO pin on the microcontroller.

Q: Can I use the HTS221 with a Raspberry Pi?
A: Yes, the HTS221 is compatible with Raspberry Pi. Use the I2C interface and appropriate libraries (e.g., Adafruit CircuitPython HTS221).

Q: What is the default I2C address of the HTS221?
A: The default I2C address is 0x5F.

Q: Can the HTS221 measure dew point?
A: The HTS221 does not directly measure dew point, but you can calculate it using the temperature and humidity readings.

Q: Is the HTS221 suitable for outdoor use?
A: The HTS221 can be used outdoors if protected from direct exposure to water, dust, and extreme conditions. Consider using an enclosure with proper ventilation.

By following this documentation, you can effectively integrate the Adafruit HTS221 into your projects for accurate environmental sensing.