// Problem with code or hardware?
// https://forum.arduino.cc/t/problem-with-code-or-hardware/1418238


const int echoPinR = 2; const int trigPinR = 3;
const int echoPinC = 6; const int trigPinC = 7;
const int echoPinL = 4; const int trigPinL = 5;
const int alertLedPinR = 8; const int alertLedPinL = 9;
const int alertLedPinC = 10;
const int buzzerR = 12; const int buzzerL = 11;

void setup() {
  pinMode(trigPinR, OUTPUT);
  pinMode(echoPinR, INPUT);
  pinMode(alertLedPinR, OUTPUT);
  pinMode(buzzerR, OUTPUT);

  pinMode(trigPinL, OUTPUT);
  pinMode(echoPinL, INPUT);
  pinMode(alertLedPinL, OUTPUT);
  pinMode(buzzerL, OUTPUT);

  pinMode(trigPinC, OUTPUT);
  pinMode(echoPinC, INPUT);
  pinMode(alertLedPinC, OUTPUT);

  Serial.begin(115200);
}

void loop() {
  unsigned long durationR, durationC, durationL;
  // unsigned long distanceR, distanceC, distanceL;
  float distanceR, distanceC, distanceL;

  digitalWrite(trigPinR, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPinR, LOW);
  durationR = pulseIn(echoPinR, HIGH, 23000UL);
  distanceR = durationR * 0.0343 / 2;
  Serial.print("Distance 1: ");
  Serial.print(distanceR);
  Serial.print(" cm");
  if (distanceR < 40) {
    digitalWrite(alertLedPinR, HIGH);
    tone(buzzerR, 1000);
  } 
  else {
    digitalWrite(alertLedPinR, LOW);
    noTone(buzzerR);
  }
  Serial.flush();

  digitalWrite(trigPinC, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPinC, LOW);
  durationC = pulseIn(echoPinC, HIGH, 23000UL);
  distanceC = durationC * 0.0343 / 2;
  Serial.print("\t Distance 2: ");
  Serial.print(distanceC);
  Serial.print(" cm");
  if (distanceC < 40) {
    digitalWrite(alertLedPinC, HIGH);

  } 
  else {
    digitalWrite(alertLedPinC, LOW);

  }
  Serial.flush();

  digitalWrite(trigPinL, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPinL, LOW);
  durationL = pulseIn(echoPinL, HIGH, 23000UL);
  distanceL = durationL * 0.0343 / 2;
  Serial.print("\t Distance 3: ");
  Serial.print(distanceL);
  Serial.println(" cm");
  if (distanceL < 40) {
    digitalWrite(alertLedPinL, HIGH);
    tone(buzzerL, 1000);
  } 
  else {
    digitalWrite(alertLedPinL, LOW);
    noTone(buzzerL);
  }
  Serial.flush();

  // delay(500);
}