/*
 HC-SR04 Ping distance sensor]
 VCC to arduino 5v GND to arduino GND
 Echo to Arduino pin 3
 Trig to Arduino pin 2
 Buzzer
 + to Arduino pin 4
 - to Arduino GND
 This sketch will also display distance values in Serial Monitor
 */

#define trigPin 2
#define echoPin 3
#define buzzer 4

void setup() {
 Serial.begin (9600);
 pinMode(trigPin, OUTPUT);
 pinMode(echoPin, INPUT);
 pinMode(buzzer, OUTPUT);
}

void loop() {
 // One process to calculating distance using HC-SR04 Ping distance sensor 
 // There are numerous examples and explinations online on how the code works
 long duration, distance;
 digitalWrite(trigPin, LOW); // Added this line
 delayMicroseconds(2); // Added this line
 digitalWrite(trigPin, HIGH);
 delayMicroseconds(10); // Added this line
 digitalWrite(trigPin, LOW);
 duration = pulseIn(echoPin, HIGH);
 distance = (duration/2) / 29.1;
 // map the input range (in this case, 0 - 135cm from the Distance Sensor)
 // to the output pitch range (2500 - 50Hz)
 // change the minimum and maximum input numbers below
 // depending on the range your sensor's giving:
 int thisPitch = map(distance, 0, 135, 2500, 50);
 // play the pitch:
 tone(buzzer, thisPitch, 10);
 Serial.print(distance);
 Serial.print(" cm ");
 Serial.print(thisPitch);
 Serial.println("Hz");
 delay(50); // delay in between reads for stability
}