Arduino library for MH-Z19/MH-Z19B CO2 sensors.
This library uses software or hardware serial to communicate with sensor. Using MHZ19 you can get CO2, temperature and accuracy values (see examples).
| Sensor | Arduino board |
|---|---|
| Vin | 5V |
| GND | GND |
| Tx | Rx |
| Rx | Tx |
When using SoftwareSerial library you should define your RX and TX pins in the constructor like this:
SoftwareSerial ss(13, 12); //rx, tx (D7, D6) on NodeMCU ESP-12eAnd then connect like in the table above, Rx to Tx and Tx to Rx.
With this library, you can get CO2 level using a single pin which supports interrupt. MHZ19PWM supports three modes:
In this mode interrupt is always attached, getCO2 method executes without significant delay.
The library attaches interrupt only when getCO2 method is called and detaches it after retrieving a single data package. All code will be delayed up to 2000ms.
In this mode, you can request the data by calling requestData method (at this moment interrupt will be attached) and then check if data are ready without blocking the main loop (isDataReady method). As in the first case getCO2 method executes without significant delay.
Aduino Nano, Arduino MEGA, ESP8266, ESP32.
Fixed bug in MHZ19PWM, now it should work on ESP8266 and ESP32
Used include guards instead of #pragma once
Refactored code to support both hardware and software serial in a more elegant way and more importantly, to support ESP32.
Initial version. Contains all changes before introducing versioning.