#define TRIG_PIN   4 // ESP32 pin GIOP26 connected to Ultrasonic Sensor's TRIG pin
#define ECHO_PIN   2 // ESP32 pin GIOP25 connected to Ultrasonic Sensor's ECHO pin
#define LED_PIN   13 // ESP32 pin GIOP17 connected to LED's pin
#define BUZZER_PIN 12 // ESP32 pin GIOP17 connected to Piezo Buzzer's pin
#define DISTANCE_THRESHOLD 100 // centimeters


// variables will change:
float duration_us, distance_cm;
unsigned long startTime, stopTime, cpuTime;

void loop(){

}

void setup() {
  Serial.begin (9600);         // initialize serial port
  pinMode(TRIG_PIN, OUTPUT);   // set ESP32 pin to output mode
  pinMode(ECHO_PIN, INPUT);    // set ESP32 pin to input mode
  pinMode(BUZZER_PIN, OUTPUT); // set ESP32 pin to output mode
  pinMode(LED_PIN, OUTPUT);  // set ESP32 pin to output mode
  xTaskCreatePinnedToCore (TaskA, "TaskA" , 1024 , NULL , 1, NULL , 1);
  xTaskCreatePinnedToCore (TaskB, "TaskB" , 1024 , NULL , 2, NULL , 1);
  xTaskCreatePinnedToCore (TaskC, "TaskC" , 1024 , NULL , 3, NULL , 1);
}

void TaskA(void*pt){
  while(1){
    startTime = micros();
  // generate 10-microsecond pulse to TRIG pin
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // measure duration of pulse from ECHO pin
  duration_us = pulseIn(ECHO_PIN, HIGH);
  // calculate the distance
  distance_cm = 0.017 * duration_us;
  stopTime = micros();
      //delay ();
  if (distance_cm < DISTANCE_THRESHOLD)
    digitalWrite(LED_PIN, HIGH); // turn on LED

  else
    digitalWrite(LED_PIN, LOW); // turn off LED
  

  // print the value to Serial Monitor
   Serial.print("distance: ");
   Serial.print(distance_cm);
   Serial.println(" cm");
   delay(500);
   cpuTime = stopTime-startTime;
    Serial.print("CPU Time(us):");
    Serial.println(cpuTime);
    Serial.println("---");
    delay(1000);
  }
}

void TaskB(void*pt) {
  while(1){
  startTime = micros();
  // generate 10-microsecond pulse to TRIG pin
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // measure duration of pulse from ECHO pin
  duration_us = pulseIn(ECHO_PIN, HIGH);
  // calculate the distance
  distance_cm = 0.017 * duration_us;
  stopTime = micros();
  if (distance_cm < DISTANCE_THRESHOLD){
    digitalWrite(BUZZER_PIN, HIGH); // turn on Piezo Buzzer
    tone(13, 262, 0.250);
  }
  else if (distance_cm > DISTANCE_THRESHOLD) {
    digitalWrite(BUZZER_PIN, LOW);  // turn off Piezo Buzzer
    noTone(13);
  }
  // print the value to Serial Monitor
  //Serial.print("distance: ");
  //Serial.print(distance_cm);
  //Serial.println(" cm");
  delay(700);
   cpuTime = stopTime-startTime;
    Serial.print("CPU Time(us):");
    Serial.println(cpuTime);
    Serial.println("---");
    delay(1000);
}
}

void TaskC( void*pt) {
  startTime = micros();
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Warning!: You are too close with this machine.");
  delay(1000);
  stopTime = micros();
   cpuTime = stopTime-startTime;
    Serial.print("CPU Time(btn):");
    Serial.println(cpuTime);
    Serial.println("---");
    delay(1000);
}