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).

With this library you can get CO2 level using single pin which supports interrupt. MHZ19PWM supports three modes:

In this mode interrupt is always attached, getCO2 method executs without significant delay.

The library attach interrupt only when getCO2 methods is called and detach it after retrieving single data package. All code will be delayed up to 2000ms.

In this mode you can request the data by calling requestData method (in this moment interrupt will be attached) and then check if data are ready without blocking main loop (isDataReady method). As in first case getCO2 method executs without significant delay.