adam exemple code

#define heatPin     5
#define buttonPin1  2
#define buttonPin2  3
#define buttonPin3  3
#define heaterTime1 1000      //en millisecond
#define heaterTime2 1000      //en millisecond
#define heaterTime3 1000      //en millisecond
#define loadTime    1000      //en millisecond

unsigned long heaterTime1Millis = 0;
unsigned long heaterTime2Millis = 0;
unsigned long heaterTime3Millis = 0;
uint8_t buttonPress = 0 ;               //button pressed

//action for btn 1 pressed
void actionBtn1Pressed(){
    buttonPress = 1;
    heaterTime1Millis = millis();
    digitalWrite(heatPin, HIGH);
}

void actionBtn2Pressed(){
    buttonPress = 2;
    heaterTime2Millis = millis();
    digitalWrite(heatPin, HIGH);
}

void actionBtn3Pressed(){
    buttonPress = 3;
    heaterTime3Millis = millis();
    digitalWrite(heatPin, HIGH);
}

void endActionButton(){
          buttonPress = 0 ;
          digitalWrite(heatPin, LOW);
          delay(loadTime);
}


void setup(){
  pinMode(buttonPin1, INPUT_PULLUP);
  pinMode(buttonPin2, INPUT_PULLUP);
  pinMode(buttonPin3, INPUT_PULLUP);
  pinMode(heatPin, OUTPUT);
}

void loop(){

  //!buttonPress ->  buttonPress == 0 or buttonPress == false
  if( !digitalRead(buttonPin1) && !buttonPress) actionBtn1Pressed();

  else if( !digitalRead(buttonPin2) && !buttonPress) actionBtn2Pressed();

  else if( !digitalRead(buttonPin3) && !buttonPress) actionBtn3Pressed();

  switch (buttonPress)
  {
  case 1:
      if( (millis() - heaterTime1Millis ) >= heaterTime1){
          //end actionBtn1
          endActionButton();
      }
    break;
  case 2:
      if( (millis() - heaterTime2Millis ) >= heaterTime2){
          //end actionBtn2
          endActionButton();
      }
    break;
  case 3:
      if( (millis() - heaterTime3Millis ) >= heaterTime3){
          //end actionBtn3
          endActionButton();
      }
    break;

  default:
    break;
  }

}