# MH-Z19/MH-Z19B Driver Test

## Introduction
This test will test if the MH-Z19 C02 gas sensor is working. The MH-Z19B seems
to be newer design which also works with this driver.

## Configuration
When testing the UART mode, set `TEST_MODE` to 1. To test the PWM mode, set
`TEST_MODE` to 2. In UART mode, make sure that `TEST_UART` points to the
interface to use. In PWM mode, make sure to define `TEST_PWM`.

## Expected result
The sensor should continuously (every 1 sec) output the CO2 ppm level. When the
sensor is disconnected, it should display a failure message every second.