//---declarations for interrupts
typedef struct {
  const uint8_t PIN;
  bool changed;
  bool value;
} fSwitch;

// SPDT switches connected to pins 27,33,15,32,14 (all adjacent in the Adafruit ESP32 Feather V2)
fSwitch FS[5] = {{37,0,0},{36,0,0},{35,0,0},{34,0,0},{33,0,0}};

volatile bool sFlag = false;
void IRAM_ATTR chkFS(void *arg) {
  fSwitch *fs = static_cast<fSwitch *>(arg);
  fs->changed = true; 
  fs->value = digitalRead(fs->PIN); 
  sFlag = true;
}

//---declarations for Buzzer
int buzzPin = 12;
int buzzChan = 0;
long buzzTimer = 0;

void setup() {
  Serial.begin(115200);
  Serial.println("Start");
  for (byte i=0; i<5; i++) {
    pinMode(FS[i].PIN,INPUT_PULLUP); 
    FS[i].value = digitalRead(FS[i].PIN); // initial state of each switch
    Serial.println("Initial State FS" + String(i) + "=" + String(FS[i].value)); 
    attachInterruptArg(FS[i].PIN,chkFS,&FS[i],CHANGE);
  } 
  ledcAttachPin(buzzPin, buzzChan);
}

void loop() {
  if (sFlag) {  // if any PIN has changed  
    ledcWriteTone(buzzChan,300); 
    buzzTimer = millis(); 
    sFlag = false;
    for (byte i=0; i<5; i++)
      if (FS[i].changed) { // determine which PIN changed
        Serial.println("Changed State FS" + String(i) + "=" + String(FS[i].value)); 
        FS[i].changed = false;
      }
  }
  if (millis() - buzzTimer > 40) ledcWriteTone(buzzChan,0); 
}