#include <M5StickC.h>  //define M5StickC hardware components and functions
#define BUTTON_MAIN 37  //The main button pin number
#define SCREEN_TIMEOUT 10 //Screen-off timeout in seconds
hw_timer_t *timer;

void IRAM_ATTR onButton() { //Interrupt on button press => turn on the screen
 detachInterrupt(BUTTON_MAIN); //Ignore more button presses
 M5.Axp.ScreenBreath(10); //Set screen light ON
 timerAlarmEnable(timer); //Start timer for screen-off delay
}

void IRAM_ATTR onTimer(){  //Interrupt on timer => turn off the screen
 timerAlarmDisable(timer); //Stop the timer.
 M5.Axp.ScreenBreath(0); //Set screen light OFF
 attachInterrupt(BUTTON_MAIN,onButton,FALLING); //Attach interrupt on button press => turn on the screen
}

void setup() {
M5.begin(); //Init M5
M5.Lcd.fillScreen(YELLOW); //Make screen yellow
pinMode(BUTTON_MAIN, INPUT_PULLUP); //Button GPIO set as input, pull-up enabled
timer=timerBegin(1,40000,true); //Init screen light timer, divisor 40000 => 0.5ms steps
timerAttachInterrupt(timer,&onTimer,true);  //Set screen light timer interrupt function
timerAlarmWrite(timer,SCREEN_TIMEOUT*2000,true); //Set interrupt to turn off screen after X timer steps of 0.5ms each.
timerAlarmEnable(timer); //Start timer for screen-off delay
}

void loop() {
  //No code here.
}