Aht20 Class Reference

Collaboration diagram for Aht20:

Public Member Functions
	Aht20 (I2cDevice &i2c)
	~Aht20 ()
void	Display ()
float	GetTemperature () const
float	GetHumidity () const

Static Public Attributes
static constexpr uint8_t	DEFAULT_I2C_ADDR = 0x38

Private Member Functions
void	InitSensor ()
void	ThreadFun ()
void	ReadSensor ()

Private Attributes
I2cDevice &	i2c_
std::thread	thread_
std::atomic< bool >	running_ {true}
float	temperature_ = 0.0f
float	humidity_ = 0.0f

Detailed Description

Definition at line 14 of file aht20.hpp.

Constructor & Destructor Documentation

Aht20()

Aht20::Aht20 ( I2cDevice &  i2c )

inlineexplicit

Constructor: initialize the sensor and start the measurement thread

Parameters

i2c	Reference to an I2C device

Definition at line 24 of file aht20.hpp.

                                 : i2c_(i2c) {
    InitSensor();
    thread_ = std::thread(&Aht20::ThreadFun, this);
  }

~Aht20()

Aht20::~Aht20 ( )

inline

Destructor: stop the background thread

Definition at line 32 of file aht20.hpp.

           {
    running_ = false;
    if (thread_.joinable()) {
      thread_.join();
    }
  }

Member Function Documentation

Display()

void Aht20::Display ( )

inline

Print current temperature and humidity to stdout

Definition at line 42 of file aht20.hpp.

                 {
    std::cout << "Temperature: " << temperature_ << " °C" << '\n';
    std::cout << "Humidity: " << humidity_ << " %RH" << '\n';
  }

GetHumidity()

float Aht20::GetHumidity ( ) const

inline

Definition at line 51 of file aht20.hpp.

{ return humidity_; }

GetTemperature()

float Aht20::GetTemperature ( ) const

inline

Definition at line 48 of file aht20.hpp.

{ return temperature_; }

InitSensor()

void Aht20::InitSensor ( )

inlineprivate

Initialize the AHT20 sensor

Definition at line 64 of file aht20.hpp.

                    {
    /* Write initialization sequence */
    i2c_.WriteRegister(0xBE, 0x08);
    i2c_.WriteRegister(0xBE, 0x00);
    std::this_thread::sleep_for(std::chrono::milliseconds(10));
  }

ReadSensor()

void Aht20::ReadSensor ( )

inlineprivate

Read and decode one sample of temperature and humidity

Definition at line 84 of file aht20.hpp.

                    {
    const uint8_t CMD[3] = {0xAC, 0x33, 0x00};
    i2c_.WriteRaw(CMD, 3); /* Send measurement command */
 
    std::this_thread::sleep_for(
        std::chrono::milliseconds(80)); /* Wait for conversion */
 
    uint8_t buf[6] = {};
    i2c_.ReadRegisters(0x00, buf, 6); /* Read 6-byte measurement data */
 
    if ((buf[0] & 0x80) != 0) {
      return; /* Sensor is busy */
    }
 
    /* Parse humidity */
    uint32_t raw_h = ((buf[1] << 12) | (buf[2] << 4) | (buf[3] >> 4));
    float humidity = static_cast<float>(raw_h) * 100.0f / 1048576.0f;
 
    if (humidity != 0.0f) {
      humidity_ = humidity;
    }
 
    /* Parse temperature */
    uint32_t raw_t = ((buf[3] & 0x0F) << 16) | (buf[4] << 8) | buf[5];
    temperature_ = static_cast<float>(raw_t) * 200.0f / 1048576.0f - 50.0f;
  }

ThreadFun()

void Aht20::ThreadFun ( )

inlineprivate

Thread function: read temperature and humidity every 500ms

Definition at line 74 of file aht20.hpp.

                   {
    while (running_) {
      ReadSensor();
      std::this_thread::sleep_for(std::chrono::milliseconds(500));
    }
  }

Field Documentation

DEFAULT_I2C_ADDR

constexpr uint8_t Aht20::DEFAULT_I2C_ADDR = 0x38

staticconstexpr

Definition at line 17 of file aht20.hpp.

humidity_

float Aht20::humidity_ = 0.0f

private

Definition at line 59 of file aht20.hpp.

i2c_

I2cDevice& Aht20::i2c_

private

Definition at line 54 of file aht20.hpp.

running_

std::atomic<bool> Aht20::running_ {true}

private

Definition at line 56 of file aht20.hpp.

{true};

temperature_

float Aht20::temperature_ = 0.0f

private

Definition at line 58 of file aht20.hpp.

thread_

std::thread Aht20::thread_

private

Definition at line 55 of file aht20.hpp.

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The documentation for this class was generated from the following file:

• src/device/aht20.hpp