#define TRIG_PIN 4
#define ECHO_PIN 

long duration;
float cm, inches;
#include <Adafruit_NeoPixel.h>
#ifdef __AVR__
 #include <avr/power.h> // Required for 16 MHz Adafruit Trinket
#endif

// Which pin on the Arduino is connected to the NeoPixels?
#define PIN        3 // On Trinket or Gemma, suggest changing this to 1

// How many NeoPixels are attached to the Arduino?
#define NUMPIXELS 3 // Popular NeoPixel ring size

// When setting up the NeoPixel library, we tell it how many pixels,
// and which pin to use to send signals. Note that for older NeoPixel
// strips you might need to change the third parameter -- see the
// strandtest example for more information on possible values.
Adafruit_NeoPixel pixels(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

#define DELAYVAL 500 // Time (in milliseconds) to pause between pixels

void setup() {
  Serial.begin(115200); // ESP32 usually uses higher baud

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
#if defined(__AVR_ATtiny85__) && (F_CPU == 16000000)
  clock_prescale_set(clock_div_1);
#endif

  
  pixels.begin(); // INITIALIZE NeoPixel strip object (REQUIRED)
}

void loop() {
  // Clean trigger
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(5);

  // Send pulse
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // Read echo
  duration = pulseIn(ECHO_PIN, HIGH);

  // Convert to distance
  cm = (duration / 2.0) / 29.1;
  inches = (duration / 2.0) / 74.0;
pixels.clear();
  // LED control
  if (cm < 18) {
     pixels.setPixelColor(0, pixels.Color(0,255, 0));

    pixels.show();   // Send the updated pixel colors to the hardware.
  } else {
         pixels.setPixelColor(0, pixels.Color(255,0, 0));

    pixels.show(); 
  }

  // Print
  Serial.print(inches);
  Serial.print(" in, ");
  Serial.print(cm);
  Serial.print(" cm");
  Serial.println();

  delay(50);
}