SHT31 / SHT31-D / GY-SHT31 / SI7021 Temperature and Humidity Sensor

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

#define I2C_MASTER_SCL_IO    22    /*!< GPIO number used for I2C master clock */
#define I2C_MASTER_SDA_IO    21    /*!< GPIO number used for I2C master data */
#define I2C_MASTER_NUM       I2C_NUM_0 /*!< I2C master I2C port number */
#define I2C_MASTER_FREQ_HZ   100000     /*!< I2C master clock frequency */
#define SHT31_SENSOR_ADDR    0x44       /*!< SHT31 I2C address */

static esp_err_t i2c_master_init(void) {
    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,
    };
    esp_err_t err = i2c_param_config(I2C_MASTER_NUM, &conf);
    if (err != ESP_OK) {
        return err;
    }
    return i2c_driver_install(I2C_MASTER_NUM, conf.mode, 0, 0, 0);
}

void read_sht31_sensor() {
    uint8_t data[6];
    uint8_t cmd[] = {0x24, 0x00}; // Single-shot, high repeatability, no clock stretching
    i2c_master_write_to_device(I2C_MASTER_NUM, SHT31_SENSOR_ADDR, cmd, 2, pdMS_TO_TICKS(1000));
    vTaskDelay(pdMS_TO_TICKS(15)); // Wait for the measurement
    i2c_master_read_from_device(I2C_MASTER_NUM, SHT31_SENSOR_ADDR, data, sizeof(data), pdMS_TO_TICKS(1000));

    uint16_t temp_raw = (data[0] << 8) | data[1];
    uint16_t hum_raw = (data[3] << 8) | data[4];

    float temperature = -45 + 175 * ((float)temp_raw / 65535.0);
    float humidity = 100 * ((float)hum_raw / 65535.0);

    printf("Temperature: %.2f °C, Humidity: %.2f %%\n", temperature, humidity);
}

void app_main() {
    ESP_ERROR_CHECK(i2c_master_init());

    while (1) {
        read_sht31_sensor();
        vTaskDelay(pdMS_TO_TICKS(2000));
    }
}

i2c:
  sda: GPIO21
  scl: GPIO22

sensor:
  - platform: sht3xd
    address: 0x44
    temperature:
      name: "Room Temperature"
    humidity:
      name: "Room Humidity"
    update_interval: 60s

[env:esp32dev]
platform = espressif32
board = esp32dev
framework = arduino
lib_deps = 
    adafruit/Adafruit SHT31 Library @ ^2.0.0
monitor_speed = 115200

#include <Wire.h>
#include "Adafruit_SHT31.h"

Adafruit_SHT31 sht31 = Adafruit_SHT31();

void setup() {
    Serial.begin(115200);
    while (!Serial) delay(10);

    if (!sht31.begin(0x44)) {   // Default I2C address for SHT31
        Serial.println("Couldn't find SHT31 sensor!");
        while (1) delay(1);
    }
}

void loop() {
    float temperature = sht31.readTemperature();
    float humidity = sht31.readHumidity();

    if (!isnan(temperature) && !isnan(humidity)) {
        Serial.print("Temperature: ");
        Serial.print(temperature);
        Serial.println(" °C");

        Serial.print("Humidity: ");
        Serial.print(humidity);
        Serial.println(" %");
    } else {
        Serial.println("Failed to read from SHT31 sensor");
    }

    delay(2000);
}

from machine import I2C, Pin
from time import sleep, sleep_ms

# The SHT31 speaks plain I2C - no driver needed (SDA=GPIO21, SCL=GPIO22)
i2c = I2C(0, scl=Pin(22), sda=Pin(21))
SHT3X_ADDR = 0x44  # 0x45 if the ADDR pin is pulled high

while True:
    i2c.writeto(SHT3X_ADDR, b'\x24\x00')  # single shot, high repeatability
    sleep_ms(20)  # wait for the measurement
    data = i2c.readfrom(SHT3X_ADDR, 6)
    temp_raw = (data[0] << 8) | data[1]
    hum_raw = (data[3] << 8) | data[4]
    temperature = -45 + 175 * temp_raw / 65535
    humidity = 100 * hum_raw / 65535
    print("Temperature: {:.2f} C".format(temperature))
    print("Humidity: {:.2f} %".format(humidity))
    sleep(2)