Add the following to void loop ().

void loop() {
M5.update();
if(M5.BtnA.wasPressed()){M5.Lcd.setRotation(3);M5.Lcd.fillScreen(TFT_BLACK);analogMeter();}
if(M5.BtnC.wasPressed()){M5.Lcd.setRotation(1);M5.Lcd.fillScreen(TFT_BLACK);analogMeter();}

The library has been released!
It is a library that can be used in common with M5Stack / Core2 / Tough / CoreInk / Paper / StickC, CPlus.
Buttons, touch panel, IMU, 5V output on / off to external port, etc. are available. It can also be used with ESP-IDF.

https://github.com/m5stack/M5Unified

https://twitter.com/lovyan03/status/1447194068866404356

@plusulli
Mac can Downoad.
It seems to be the download method for PC or Windows.

1. DownLoad : lv_ccs811_m5stack.zip_-1.pdf

2. Delete _-1.pdf

3. Unzip the .zip
   lv_ccs811_m5stack.zip

How to run LVGL on M5Stack
https://forum.m5stack.com/topic/3613/how-to-run-lvgl-on-m5stack/1

LVGL ( Light and Versatile Graphics Library )
https://lvgl.io/

How to run LVGL on M5Stack ( ESP32 ) : 2021.06.18
https://macsbug.wordpress.com/2021/06/18/how-to-run-lvgl-on-m5stack-esp32/
( Demo of M5Stack and M5Core2 )

LVGL with M5Stack Part 2 : 2021.07.03
https://macsbug.wordpress.com/2021/07/03/lvgl-with-m5stack-part-2/

CO2 monitor with M5Stack and LVGL : 2021.07.05
https://macsbug.wordpress.com/2021/07/05/co2-monitor-with-m5stack-and-lvgl/

Countermeasure: Turn on the ADC Power of GPIO39.

#include <driver/adc.h>
void setup(){
adc_power_acquire(); // ADC Power ON

The countermeasures have been clarified by the investigation and analysis of Mr. nao *.
https://twitter.com/mikasa231/status/1403576681701335044
We would like to thank Mr. nao * for his efforts.

ded it to my blog. Postscript: 2021.06.13
ButtonA on M5Stack does not work properly
https://macsbug.wordpress.com/2021/05/02/buttona-on-m5stack-does-not-work-properly/

@aattila

Very great!

arduino-esp32 version 1.0.5-rcX
The compiled project will not work consistently because there is a wifi related bug and sometimes the button A (left) will receive the pushed event (many events)

This problem should be cured after wifi.setSleep (False) after wifi.begin.
Please refer to the following.
https://macsbug.wordpress.com/2021/05/02/buttona-on-m5stack-does-not-work-properly/

This is a report of measures for the A button of M5Stack and the B button of M5Stick C to operate without permission.
Workaround：WiFi.setSleep(false);

ButtonA on M5Stack does not work properly : May 02, 2021
https://macsbug.wordpress.com/2021/05/02/buttona-on-m5stack-does-not-work-properly/