ESP32 MH-Z19 NDIR CO₂ Sensor

Code Examples

Below you can find code examples of MH-Z19 NDIR CO₂ Sensor with ESP32 in several frameworks:

• Arduino IDE
• ESP-IDF
• ESPHome
• PlatformIO
• MicroPython

ESP32 MH-Z19 Arduino IDE Code Example

Example in Arduino IDE

Fill in your main Arduino IDE sketch file with the following code to use the MH-Z19 NDIR CO₂ Sensor:

#include <SoftwareSerial.h>

SoftwareSerial mySerial(10, 11); // RX, TX

void setup() {
    Serial.begin(9600);
    mySerial.begin(9600);
}

void loop() {
    byte cmd[9] = {0xFF, 0x01, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x79};
    mySerial.write(cmd, 9);
    delay(500);
    if (mySerial.available()) {
        byte response[9];
        mySerial.readBytes(response, 9);
        if (response[0] == 0xFF && response[1] == 0x86) {
            int CO2 = (response[2] << 8) + response[3];
            Serial.print("CO2 Concentration: ");
            Serial.print(CO2);
            Serial.println(" ppm");
        }
    }
    delay(2000);
}

This Arduino sketch interfaces with the MH-Z19 sensor using software serial. It sends a command to request CO₂ concentration data and processes the response. The CO₂ concentration in ppm is displayed in the Serial Monitor every 2.5 seconds.

Connect your ESP32 to your computer via a USB cable, Ensure the correct Board and Port are selected under Tools, Click the "Upload" button in the Arduino IDE to compile and upload the code to your ESP32.

ESP32 MH-Z19 ESP-IDF Code Example

Example in Espressif IoT Framework (ESP-IDF)

If you're using ESP-IDF to work with the MH-Z19 NDIR CO₂ Sensor, here's how you can set it up and read data from the sensor. Fill in this code in the main ESP-IDF file:

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

#define UART_NUM UART_NUM_1
#define TXD_PIN (GPIO_NUM_17)
#define RXD_PIN (GPIO_NUM_16)

void app_main(void) {
    const uart_config_t uart_config = {
        .baud_rate = 9600,
        .data_bits = UART_DATA_8_BITS,
        .parity = UART_PARITY_DISABLE,
        .stop_bits = UART_STOP_BITS_1,
        .flow_ctrl = UART_HW_FLOWCTRL_DISABLE
    };
    uart_param_config(UART_NUM, &uart_config);
    uart_set_pin(UART_NUM, TXD_PIN, RXD_PIN, UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE);
    uart_driver_install(UART_NUM, 256, 0, 0, NULL, 0);

    uint8_t cmd[9] = {0xFF, 0x01, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x79};
    uint8_t response[9];

    while (1) {
        uart_write_bytes(UART_NUM, (const char *)cmd, 9);
        vTaskDelay(pdMS_TO_TICKS(500));

        int len = uart_read_bytes(UART_NUM, response, 9, pdMS_TO_TICKS(1000));
        if (len == 9 && response[0] == 0xFF && response[1] == 0x86) {
            int CO2 = (response[2] << 8) | response[3];
            printf("CO2 Concentration: %d ppm\n", CO2);
        }
        vTaskDelay(pdMS_TO_TICKS(2000));
    }
}

This ESP-IDF example configures UART for communication with the MH-Z19 sensor. It sends a command to request CO₂ concentration, reads the response, and calculates the CO₂ concentration in ppm. The result is printed to the console every 2.5 seconds.

Update the I2C pins (I2C_MASTER_SDA_IO and I2C_MASTER_SCL_IO) to match your ESP32 hardware setup, Use idf.py build to compile the project, Use idf.py flash to upload the code to your ESP32.

ESP32 MH-Z19 ESPHome Code Example

Example in ESPHome (Home Assistant)

Fill in this configuration in your ESPHome YAML configuration file (example.yml) to integrate the MH-Z19 NDIR CO₂ Sensor

uart:
  tx_pin: GPIO17
  rx_pin: GPIO16
  baud_rate: 9600

sensor:
  - platform: mhz19
    co2:
      name: "MH-Z19 CO2"
    temperature:
      name: "MH-Z19 Temperature"
    update_interval: 60s

This ESPHome configuration interfaces with the MH-Z19 sensor over UART using GPIO17 (TX) and GPIO16 (RX). The CO₂ concentration and temperature are read every 60 seconds and displayed as named sensors. The UART baud rate is set to 9600.

Upload this code to your ESP32 using the ESPHome dashboard or the esphome run command.

ESP32 MH-Z19 PlatformIO Code Example

Example in PlatformIO Framework

For PlatformIO, make sure to configure the platformio.ini file with the appropriate environment and libraries, and then proceed with the code.

Configure platformio.ini

First, your platformio.ini should look like below. You might need to include some libraries as shown. Make sure to change the board to your ESP32:

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

ESP32 MH-Z19 PlatformIO Example Code

Write this code in your PlatformIO project under the src/main.cpp file to use the MH-Z19 NDIR CO₂ Sensor:

#include <MHZ19.h>
#include <SoftwareSerial.h>

SoftwareSerial mySerial(16, 17); // RX, TX
MHZ19 myMHZ19;

void setup() {
    Serial.begin(115200);
    mySerial.begin(9600);
    myMHZ19.begin(mySerial);
    myMHZ19.autoCalibration();
}

void loop() {
    int co2 = myMHZ19.getCO2();
    float temp = myMHZ19.getTemperature();

    if (co2 > 0) {
        Serial.print("CO2 Concentration: ");
        Serial.print(co2);
        Serial.println(" ppm");
    } else {
        Serial.println("Error reading CO2 concentration");
    }

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

    delay(5000);
}

This PlatformIO example uses the MHZ19 library to interface with the MH-Z19 sensor over SoftwareSerial. The sensor's CO₂ concentration and temperature are printed every 5 seconds. Automatic calibration is enabled.

Upload the code to your ESP32 using the PlatformIO "Upload" button in your IDE or the pio run --target upload command.

ESP32 MH-Z19 MicroPython Code Example

Example in Micro Python Framework

Fill in this script in your MicroPython main.py file (main.py) to integrate the MH-Z19 NDIR CO₂ Sensor with your ESP32.

from machine import UART, Pin
import time

uart = UART(2, baudrate=9600, tx=Pin(17), rx=Pin(16))

cmd = bytearray([0xFF, 0x01, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x79])

def read_co2():
    uart.write(cmd)
    time.sleep(0.1)
    if uart.any():
        response = uart.read(9)
        if len(response) == 9 and response[0] == 0xFF and response[1] == 0x86:
            co2 = (response[2] << 8) | response[3]
            return co2
    return None

while True:
    co2 = read_co2()
    if co2 is not None:
        print(f"CO2 Concentration: {co2} ppm")
    else:
        print("Error reading CO2 concentration")
    time.sleep(2)

This MicroPython script interfaces with the MH-Z19 sensor using UART (GPIO17 TX, GPIO16 RX). The script sends a command to request CO₂ concentration and parses the response. The CO₂ concentration in ppm is printed every 2 seconds, and errors during communication are handled gracefully.

Upload this code to your ESP32 using a MicroPython-compatible IDE, such as Thonny, uPyCraft, or tools like ampy.