How To Make A Distance Meter Using Ultrasonic Sensor

Hello friends, this is my new project using ultrasonic sensor. Actually this is distance meter which show the result on centimeter, Inch, meter also pause and reset option using button.

Components :

1. Arduino Nano :
2. HC-SR04 Ultrasonic Sensor
3. TP-4056 Charging Module
4. Lithium Battery
5. SSD 1306 Module
6. Push Switch
7. 10K resistor
8. ON-OFF Switch
9. MDF Board

Diagram :

Code:

#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

int state=0;
int sense=0;

#define trigPin 13
#define echoPin 12

const int buttonPin1 = 3;
const int buttonPin2 = 4;
const int buttonPin3 = 5;

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     6 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
int buttonState = 0;  
int buttonState2 = 0;
int buttonState3 = 0;  

void setup() {
  Serial.begin (9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(buttonPin1, INPUT);
  pinMode(buttonPin2, INPUT);
  pinMode(buttonPin3, INPUT);
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C); //initialize with the I2C addr 0x3C (128x64)
  

     display.setCursor(2,0);  //oled display
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.println("Distance");
  display.println("Meter");
  delay(5000);
  display.clearDisplay();
  

}

void loop() {
  float duration, distance;

  if(sense==0){
  digitalWrite(trigPin, LOW);  //PULSE ___|---|___
  delayMicroseconds(2); 
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10); 
  digitalWrite(trigPin, LOW);
  
  duration = pulseIn(echoPin, HIGH);
  }
  
   if(state==0){
  distance = (duration/2) / 29.1;
  display.setCursor(2,10);  //oled display
  display.setTextSize(3);
  display.setTextColor(WHITE);
  if(distance<100){
  display.println(distance);
   }
   else{
    display.println(distance,1);
   }
   }
   if(state==1){
  distance = (duration/2) / 73.914;
    display.setCursor(2,10);  //oled display
  display.setTextSize(3);
  display.setTextColor(WHITE);
  if(distance<100){
  display.println(distance);
   }
   else{
    display.println(distance,1);
   }
   }
   if(state==2){
  distance = (duration/2) / 29.1;
  distance=distance/100;
      display.setCursor(2,10);  //oled display
  display.setTextSize(3);
  display.setTextColor(WHITE);
  display.println(distance);
   }

  
  display.setCursor(100,15);
  display.setTextSize(2);
  
  if(state==0){
  display.println("cm");
  }
  if(state==1){
  display.println("in");
  }
  if(state==2){
  display.println("m");
  }
  
  display.display();

  delay(500);
  display.clearDisplay();
 
  
  buttonState = digitalRead(buttonPin1);
  buttonState2 = digitalRead(buttonPin2);
  if (buttonState2 == HIGH) {
   sense=1;
  }
  buttonState3 = digitalRead(buttonPin3);
   if (buttonState3 == HIGH) {
   sense=0;
  }

  // check if the pushbutton is pressed. If it is, the buttonState is HIGH:
  if (buttonState == HIGH) {
   
    if(state<=2){
      state=state+1;
    }
    else{
      state=0;
    }
  }
  Serial.println(distance);//debug
  Serial.println(state);//debug
  Serial.println(sense);//debug

}