esp-idf-lib/components/mhz19b/README.md

# Driver for the MH-Z19B NDIR CO2 sensor

This driver is heavily inspired from [Erriez MH-Z19B CO2 sensor library for
Arduino](https://github.com/Erriez/ErriezMHZ19B).

It uses an UART serial port to communicate with the sensor. Since the UART
must configured a specific way (9600 8N1), the `mhz19b_init()` takes care of
configuring it.  It will however not start detecting/reading from the sensor.
This must be done. Typical usage would be:

```C
[...]
#include "esp_log.h"
#include "mhz19b.h"

#define MHZ19B_TX 12
#define MHZ19B_RX 13

void app_main(void)
{
    int16_t co2;
    mhz19b_dev_t dev;
    char version[6];
    uint16_t range;
    bool autocal;

    mhz19b_init(&dev, UART_NUM_1, MHZ19B_TX, MHZ19B_RX);

    while (!mhz19b_detect(&dev))
    {
        ESP_LOGI(TAG, "MHZ-19B not detected, waiting...");
        vTaskDelay(1000 / portTICK_PERIOD_MS);
    }

    mhz19b_get_version(&dev, version, 5);
    ESP_LOGI(TAG, "MHZ-19B firmware version: %s", version);
    ESP_LOGI(TAG, "MHZ-19B set range and autocal");

    mhz19b_set_range(&dev, MHZ19B_RANGE_5000);
    mhz19b_set_auto_calibration(&dev, false);

    mhz19b_get_range(&dev, &range);
    ESP_LOGI(TAG, "  range: %d", range);

    mhz19b_get_auto_calibration(&dev, &autocal);
    ESP_LOGI(TAG, "  autocal: %s", autocal ? "ON" : "OFF");

    while (mhz19b_is_warming_up(&dev))
    {
        ESP_LOGI(TAG, "MHZ-19B is warming up");
        vTaskDelay(1000 / portTICK_PERIOD_MS);
    }

    while (1) {
        mhz19b_read_CO2(&dev, &co2);
        ESP_LOGI(TAG, "CO2: %d", co2);
        vTaskDelay(5000 / portTICK_PERIOD_MS);
    }
}

```