Identification of Basic Logic Gate ICs using Arduino

/*
 
  This sketch can identify NOT, AND, NAND, OR, NOR, and XOR Gate ICs.
  When a gate is connected and a button is pressed, Arduino identifies
  the gate IC.
 
  This program is for LCD without I2C Module or without LCD
 
  This program is written by Shreyas for Electronics Champ YouTube Channel.
  Please subscribe to this channel. Thank You.
 
*/
 
//Including the libraries
#include <LiquidCrystal.h>
 
const int rs = 12, en = 11, d4 = 10, d5 = 9, d6 = 8, d7 = 7;
 
//Define the variables
int in1 = 3;
int in2 = 4;
int out = 5;
int button = 6;
String gate = "";
 
//Create LCD object
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
 
void setup() {
 
  //Start Serial communication
  Serial.begin(9600);
 
  //Set pinModes
  pinMode(in1, OUTPUT);
  pinMode(in2, OUTPUT);
  pinMode(button, INPUT);
  pinMode(out, INPUT);
 
  //Initialize the lcd
  lcd.begin(16, 2);
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Electronics");
  lcd.setCursor(0, 1);
  lcd.print("Champ");
  Serial.println("Electronics Champ");
  delay(3000);
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Place a Gate and");
  lcd.setCursor(0, 1);
  lcd.print("press the button");
  Serial.println("Place a Gate and press the button");
 
}
 
void loop() {
 
  if (digitalRead(button) == HIGH) { //If the button is pressed...
 
    //Check if the gate is NOT or NOR
    checkNOT();
    checkNOR();
 
    //If the gate is neither NOR nor NOT, check for other gates
    if (gate == "") {
      digitalWrite(in1, 0);
      digitalWrite(in2, 0);
 
      if (digitalRead(out) == 0) {
        digitalWrite(in1, 0);
        digitalWrite(in2, 1);
 
        if (digitalRead(out) == 0) {
          gate = "AND";
        }
 
        else if (digitalRead(out) == 1) {
          digitalWrite(in1, 1);
          digitalWrite(in2, 1);
 
          if (digitalRead(out) == 0) {
            gate = "XOR";
          }
 
          else {
            gate = "OR";
          }
        }
      }
 
      else if (digitalRead(out) == 1) {
        gate = "NAND";
      }
    }
 
    if (isGatePresent() == true) { //If a gate IS PLACED AND the button is pressed...
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Gate: Logic ");
      lcd.print(gate);
      Serial.print("Gate: Logic ");
      Serial.print(gate);
      Serial.println();
      pinMode(in1, OUTPUT);
      pinMode(in2, INPUT);
      digitalWrite(in1, 0);
      delay(1000);
      gate = "";
    }
 
    else {
      checkNOT();
 
      if (gate != "NOT") {
        Serial.println("Place a gate for classification!!");
        lcd.clear();
        lcd.setCursor(0, 0);
        lcd.print("Place a gate for");
        lcd.setCursor(0, 1);
        lcd.print("classification!!");
        digitalWrite(in1, HIGH);
        digitalWrite(in2, LOW);
        gate = "";
        delay(2000);
      }
 
      else if (gate == "NOT") {
        lcd.clear();
        lcd.setCursor(0, 0);
        lcd.print("Gate: Logic ");
        lcd.print("NOT");
        Serial.print("Gate: Logic ");
        Serial.print("NOT");
        Serial.println();
        pinMode(in1, OUTPUT);
        pinMode(in2, INPUT);
        digitalWrite(in1, 0);
        delay(1000);
        gate = "";
      }
 
    }
 
  }
 
}
 
void checkNOR() { //Check if the gate is NOR Gate
 
  pinMode(out, OUTPUT);
  pinMode(in1, INPUT);
  digitalWrite(out, 0);
  digitalWrite(in2, 0);
 
  if (digitalRead(in1) == 1) {
    digitalWrite(out, 0);
    digitalWrite(in2, 1);
 
    if (digitalRead(in1) == 0) {
      digitalWrite(out, 1);
      digitalWrite(in2, 0);
 
      if (digitalRead(in1) == 0) {
        digitalWrite(out, 1);
        digitalWrite(in2, 1);
 
        if (digitalRead(in1) == 0) {
          gate = "NOR";
        }
      }
    }
  }
 
  pinMode(in1, OUTPUT);
  pinMode(in2, OUTPUT);
  pinMode(button, INPUT);
  pinMode(out, INPUT);
 
}
 
void checkNOT() { //Check if the gate is NOT Gate
 
  pinMode(in2, INPUT);
  digitalWrite(in1, 0);
 
  if (digitalRead(in2) == 1) {
    digitalWrite(in1, 1);
 
    if (digitalRead(in2) == 0) {
      gate = "NOT";
      pinMode(in1, OUTPUT);
      pinMode(in2, INPUT);
    }
  }
 
  pinMode(in2, OUTPUT);
 
}
 
boolean isGatePresent() { //Check if a gate is placed
 
  digitalWrite(in1, 0);
  digitalWrite(in2, 0);
 
  if (digitalRead(out) == 0) {
    digitalWrite(in1, 0);
    digitalWrite(in2, 1);
 
    if (digitalRead(out) == 0) {
      digitalWrite(in1, 1);
      digitalWrite(in2, 0);
 
      if (digitalRead(out) == 0) {
        digitalWrite(in1, 1);
        digitalWrite(in2, 1);
 
        if (digitalRead(out) == 0) {
          checkNOR();
          checkNOT();
 
          if (gate != "NOR" and gate != "NOT") {
            return false;
          }
 
        }
 
        else {
          return true;
        }
 
      }
 
      else {
        return true;
      }
 
    }
 
    else {
      return true;
    }
 
  }
 
  else {
    return true;
  }
 
}