AHT20 Temperature and Humidity Sensor

#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/i2c.h"

#define I2C_MASTER_NUM I2C_NUM_0         // I2C port number
#define I2C_MASTER_SDA_IO 21            // GPIO for SDA
#define I2C_MASTER_SCL_IO 22            // GPIO for SCL
#define I2C_MASTER_FREQ_HZ 100000       // I2C clock frequency
#define AHT20_ADDR 0x38                 // I2C address of the AHT20 sensor
#define AHT20_CMD_TRIGGER 0xAC          // Command to trigger measurement
#define AHT20_CMD_SOFTRESET 0xBA        // Command to reset the sensor
#define AHT20_CMD_INIT 0xBE             // Command to initialize the sensor

// Function to initialize I2C
void i2c_master_init() {
    i2c_config_t conf = {
        .mode = I2C_MODE_MASTER,
        .sda_io_num = I2C_MASTER_SDA_IO,
        .scl_io_num = I2C_MASTER_SCL_IO,
        .sda_pullup_en = GPIO_PULLUP_ENABLE,
        .scl_pullup_en = GPIO_PULLUP_ENABLE,
        .master.clk_speed = I2C_MASTER_FREQ_HZ,
    };
    i2c_param_config(I2C_MASTER_NUM, &conf);
    i2c_driver_install(I2C_MASTER_NUM, conf.mode, 0, 0, 0);
}

// Function to write data to the AHT20
esp_err_t aht20_write_command(uint8_t cmd) {
    i2c_cmd_handle_t handle = i2c_cmd_link_create();
    i2c_master_start(handle);
    i2c_master_write_byte(handle, (AHT20_ADDR << 1) | I2C_MASTER_WRITE, true);
    i2c_master_write_byte(handle, cmd, true);
    i2c_master_stop(handle);
    esp_err_t ret = i2c_master_cmd_begin(I2C_MASTER_NUM, handle, pdMS_TO_TICKS(1000));
    i2c_cmd_link_delete(handle);
    return ret;
}

// Function to read data from the AHT20
esp_err_t aht20_read_data(uint8_t *data, size_t length) {
    i2c_cmd_handle_t handle = i2c_cmd_link_create();
    i2c_master_start(handle);
    i2c_master_write_byte(handle, (AHT20_ADDR << 1) | I2C_MASTER_READ, true);
    i2c_master_read(handle, data, length, I2C_MASTER_LAST_NACK);
    i2c_master_stop(handle);
    esp_err_t ret = i2c_master_cmd_begin(I2C_MASTER_NUM, handle, pdMS_TO_TICKS(1000));
    i2c_cmd_link_delete(handle);
    return ret;
}

// Function to reset and initialize the AHT20
void aht20_init() {
    aht20_write_command(AHT20_CMD_SOFTRESET);
    vTaskDelay(pdMS_TO_TICKS(20)); // Wait after reset
    aht20_write_command(AHT20_CMD_INIT);
    vTaskDelay(pdMS_TO_TICKS(20)); // Wait for initialization
}

// Function to get temperature and humidity
void aht20_get_temp_humidity(float *temperature, float *humidity) {
    uint8_t data[6];
    aht20_write_command(AHT20_CMD_TRIGGER);
    vTaskDelay(pdMS_TO_TICKS(80)); // Wait for the measurement

    if (aht20_read_data(data, 6) == ESP_OK) {
        uint32_t raw_humidity = ((data[1] << 16) | (data[2] << 8) | data[3]) >> 4;
        uint32_t raw_temperature = ((data[3] & 0x0F) << 16) | (data[4] << 8) | data[5];

        *humidity = ((float)raw_humidity / 1048576.0) * 100.0;
        *temperature = ((float)raw_temperature / 1048576.0) * 200.0 - 50.0;
    } else {
        *humidity = -1.0;
        *temperature = -1.0;
    }
}

// Main application
void app_main() {
    float temperature = 0.0, humidity = 0.0;

    i2c_master_init();
    aht20_init();

    while (1) {
        aht20_get_temp_humidity(&temperature, &humidity);
        printf("Temperature: %.2f °C, Humidity: %.2f %%", temperature, humidity);
        vTaskDelay(pdMS_TO_TICKS(2000));
    }
}