Basic Ultrasonic

/*
 * Basic Ultrasonic
 * by Tyson Moll
 *
 * References:
 * Ultrasonic Tutorial by Rui Santos, https://randomnerdtutorials.com
 *
 */
#include <Wire.h>
#include <ArduinoJson.h>

// Ultrasonic
int trigPin = 5;    // Ultrasonic Trigger
int echoPin = 6;    // Ultrasonic Echo
long duration, cm; // Units for Ultrasonic
unsigned long lastSend, sonicCount;
int sendRate = 50;
int sonicRate = sendRate;

// Thermochromic Pins
int ledPin = 7;
int chromicPin = 4;
int dist = 10; // Distance to light at

void setup() {
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT); // Ultrasonic
  pinMode(echoPin, INPUT);
  pinMode(ledPin, OUTPUT); // Thermochromics
  pinMode(chromicPin, OUTPUT);
}

void loop() {

  // Ultrasonic
  if (millis() - sonicCount >= sonicRate) {
    digitalWrite(trigPin, LOW); // LOW clearing ensures clean HIGH pulse
    delayMicroseconds(5); // 0.000005 seconds
    digitalWrite(trigPin, HIGH); // Triggers ultrasonic signal
    delayMicroseconds(10);
    digitalWrite(trigPin, LOW);

    // Read the signal from the sensor: a HIGH pulse whose
    // duration is the time (in microseconds) from the sending
    // of the ping to the reception of its echo off of an object.
    pinMode(echoPin, INPUT);
    duration = pulseIn(echoPin, HIGH);

    // Convert the time into a distance
    cm = (duration/2) / 29.1;     // Divide by 29.1 or multiply by 0.0343

    Serial.print(cm); // Report unit distance
    Serial.print("cm");
    Serial.println();
  }

  if (cm > dist) {
    digitalWrite(ledPin, HIGH);
    digitalWrite(chromicPin, HIGH);
  } else {
    digitalWrite(ledPin, LOW);
    digitalWrite(chromicPin, LOW);
  }

  delay(100);
}