HTE501 Temperature and Humidity Sensor

// The HTE501 is an E+E Elektronik sensor with its own I2C protocol (address 0x40) -
// it is NOT compatible with SHT3x commands.
#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/i2c.h"

#define I2C_MASTER_SCL_IO    22       // GPIO number for I2C SCL
#define I2C_MASTER_SDA_IO    21       // GPIO number for I2C SDA
#define I2C_MASTER_NUM       I2C_NUM_0
#define I2C_MASTER_FREQ_HZ   100000
#define HTE501_SENSOR_ADDR   0x40     // HTE501 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_ERROR_CHECK(i2c_param_config(I2C_MASTER_NUM, &conf));
    return i2c_driver_install(I2C_MASTER_NUM, conf.mode, 0, 0, 0);
}

void read_hte501_sensor(void) {
    // Single-shot measurement command 0x2C1B (clock stretching enabled)
    uint8_t cmd[] = {0x2C, 0x1B};
    uint8_t data[6]; // T MSB, T LSB, CRC, RH MSB, RH LSB, CRC

    if (i2c_master_write_to_device(I2C_MASTER_NUM, HTE501_SENSOR_ADDR, cmd, 2, pdMS_TO_TICKS(1000)) != ESP_OK) {
        printf("HTE501 not found - check wiring\n");
        return;
    }
    vTaskDelay(pdMS_TO_TICKS(20)); // Wait for the measurement

    if (i2c_master_read_from_device(I2C_MASTER_NUM, HTE501_SENSOR_ADDR, data, 6, pdMS_TO_TICKS(1000)) == ESP_OK) {
        int16_t raw_temp = (data[0] << 8) | data[1]; // signed
        uint16_t raw_hum = (data[3] << 8) | data[4];
        // Scaling per the E+E datasheet: both values are hundredths
        float temperature = raw_temp / 100.0;
        float humidity = raw_hum / 100.0;
        printf("Temperature: %.2f C, Humidity: %.2f %%\n", temperature, humidity);
    }
}

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

    while (1) {
        read_hte501_sensor();
        vTaskDelay(pdMS_TO_TICKS(2000));
    }
}

i2c:
  sda: GPIO21
  scl: GPIO22

sensor:
  - platform: hte501
    temperature:
      name: "Office Temperature"
    humidity:
      name: "Office Humidity"
    address: 0x40
    update_interval: 60s

[env:esp32dev]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200

#include <Arduino.h>
// The HTE501 is an E+E Elektronik sensor with its own I2C protocol - no external
// library is needed. I2C address 0x40; SDA=GPIO21, SCL=GPIO22 (ESP32 defaults).
#include <Wire.h>

#define HTE501_ADDR 0x40

void setup() {
  Serial.begin(115200);
  Wire.begin(); // SDA=GPIO21, SCL=GPIO22
}

void loop() {
  // Single-shot measurement command 0x2C1B (with I2C clock stretching)
  Wire.beginTransmission(HTE501_ADDR);
  Wire.write(0x2C);
  Wire.write(0x1B);
  if (Wire.endTransmission() == 0) {
    delay(20); // Wait for the measurement to finish

    // Response: T MSB, T LSB, CRC, RH MSB, RH LSB, CRC
    Wire.requestFrom(HTE501_ADDR, 6);
    if (Wire.available() == 6) {
      uint8_t b[6];
      for (int i = 0; i < 6; i++) b[i] = Wire.read();

      int16_t rawTemp = (b[0] << 8) | b[1];      // signed
      uint16_t rawHum = (b[3] << 8) | b[4];
      float temperature = rawTemp / 100.0;       // scaling per E+E datasheet
      float humidity = rawHum / 100.0;

      Serial.print("Temperature: ");
      Serial.print(temperature);
      Serial.println(" C");
      Serial.print("Humidity: ");
      Serial.print(humidity);
      Serial.println(" %");
    }
  } else {
    Serial.println("HTE501 not found - check wiring");
  }
  delay(2000);
}

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

# The HTE501 is an E+E Elektronik sensor with its own I2C protocol - no driver needed
i2c = I2C(0, scl=Pin(22), sda=Pin(21))
HTE501_ADDR = 0x40

while True:
    i2c.writeto(HTE501_ADDR, b'\x2c\x1b')  # single-shot measurement command
    sleep_ms(20)  # wait for the measurement
    data = i2c.readfrom(HTE501_ADDR, 6)  # T MSB, T LSB, CRC, RH MSB, RH LSB, CRC
    raw_temp = (data[0] << 8) | data[1]
    if raw_temp > 55536:  # negative temperatures are offset by 65536
        raw_temp -= 65536
    raw_hum = (data[3] << 8) | data[4]
    # Scaling per the E+E datasheet: both values are hundredths
    print("Temperature: {:.2f} C".format(raw_temp / 100))
    print("Humidity: {:.2f} %".format(raw_hum / 100))
    sleep(2)