Robot Car - Shift Register, Sensors, and App interfacing

#define CUSTOM_SETTINGS
#define INCLUDE_GAMEPAD_MODULE
#define INCLUDE_TERMINAL_MODULE

#include <Dabble.h>
#include <ShiftRegister74HC595.h>
#include <Wire.h>
#include <SFE_BMP180.h>
#include <MQ2.h>
#include <dht.h>

int numberOfShiftRegisters = 1; 
int serialDataPin = 12; 
int clockPin = 10; 
int latchPin = 11; 

ShiftRegister74HC595<1> sr(serialDataPin, clockPin, latchPin);

SFE_BMP180 bmp180;
dht DHT;

const int dht = 5;

String str = "Pressure Sensor ";
String str1 = "Gas Sensor ";
String str2 = "Humidity Sensor ";
String str3 = "Light Sensor ";

const int GAS_SENSOR = A6;
int lpg, co, smoke;

MQ2 mq2(GAS_SENSOR);

const int ENA = 0;
const int N1 = 1;
const int N2 = 2;
const int N3 = 3;
const int N4 = 4;
const int ENB = 5;

const int HEADLIGHT = 6;
int HEADLIGHT_STATUS = HIGH;
unsigned long previousMillis = 0;
const long interval = 500;

const int BACKLIGHT = 7;

const int RIGHT = A3;
const int MIDDLE = A2;
const int LEFT = A1;

int rightRead, middleRead, leftRead;

int wheelsState = 1;

const int FRONT1 = 9;
const int FRONT2 = 8;

const int BACK1 = 7;
const int BACK2 = 6;

int front1Read, front2Read, back1Read, back2Read;

const int LDR = A7;

void setup()
{
  pinMode(GAS_SENSOR, INPUT);

  Dabble.begin(9600);
  Serial.begin(9600);

  sr.set(HEADLIGHT, HIGH);

  pinMode(FRONT1, INPUT);
  pinMode(FRONT2, INPUT);
  pinMode(BACK1, INPUT);
  pinMode(BACK2, INPUT);

  mq2.begin();
  bool success = bmp180.begin();

  if (success) {
    Serial.println("BMP180 init success");
  }
}

void buttonRead()
{
  if (wheelsState == HIGH) {
    if (GamePad.isUpPressed())
    {
      Serial.println("Up");
      sr.set(BACKLIGHT, LOW);
      sr.set(ENA, HIGH);
      sr.set(N1, LOW);
      sr.set(N2, HIGH);
      sr.set(ENB, HIGH);
      sr.set(N3, HIGH);
      sr.set(N4, LOW);
    }

    else if (GamePad.isDownPressed())
    {
      Serial.println("Down");
      sr.set(BACKLIGHT, HIGH);
      sr.set(ENA, HIGH);
      sr.set(N1, HIGH);
      sr.set(N2, LOW);
      sr.set(ENB, HIGH);
      sr.set(N3, LOW);
      sr.set(N4, HIGH);
    }

    else if (GamePad.isLeftPressed())
    {
      Serial.println("Left");
      sr.set(BACKLIGHT, LOW);
      sr.set(ENA, HIGH);
      sr.set(N1, HIGH);
      sr.set(N2, LOW);
      sr.set(ENB, HIGH);
      sr.set(N3, HIGH);
      sr.set(N4, LOW);
    }

    else if (GamePad.isRightPressed())
    {
      Serial.println("Right");
      sr.set(BACKLIGHT, LOW);
      sr.set(ENA, HIGH);
      sr.set(N1, LOW);
      sr.set(N2, HIGH);
      sr.set(ENB, HIGH);
      sr.set(N3, LOW);
      sr.set(N4, HIGH);
    }
    else
    {
      sr.set(ENA, LOW);
      sr.set(N1, LOW);
      sr.set(N2, LOW);
      sr.set(ENB, LOW);
      sr.set(N3, LOW);
      sr.set(N4, LOW);
    }
  }
  else
  {
    sr.set(ENA, LOW);
    sr.set(N1, LOW);
    sr.set(N2, LOW);
    sr.set(ENB, LOW);
    sr.set(N3, LOW);
    sr.set(N4, LOW);
  }
}
void headLights() {
  if (GamePad.isTrianglePressed()) {
    unsigned long currentMillis = millis();

    if (currentMillis - previousMillis >= interval) {
      previousMillis = currentMillis;

      HEADLIGHT_STATUS = !HEADLIGHT_STATUS;
      sr.set(HEADLIGHT, HEADLIGHT_STATUS);
    }
  }
}

void sensorReadings()
{
  if (Terminal.available() > 0) {
    if (Terminal.compareString(str)) {
      char status;
      double T, P;
      bool success = false;

      status = bmp180.startTemperature();

      if (status != 0) {
        delay(1000);
        status = bmp180.getTemperature(T);

        if (status != 0) {
          status = bmp180.startPressure(3);

          if (status != 0) {
            delay(status);
            status = bmp180.getPressure(P, T);

            if (status != 0) {
              Terminal.println("Pressure: ");
              Terminal.println(P);
              Terminal.println(" hPa");

              Terminal.println("Temperature: ");
              Terminal.println(T);
              Terminal.println("C");
            }
          }
        }
      }
    }
    else if (Terminal.compareString(str1)) {
      float* values = mq2.read(true);
      lpg = mq2.readLPG();
      co = mq2.readCO();
      smoke = mq2.readSmoke();

      Terminal.println("LPG");
      Terminal.println(lpg);
      Terminal.println("CO2");
      Terminal.println(co);
      Terminal.println("Smoke");
      Terminal.println(smoke);
      Terminal.println("PPM");
    }
    else if (Terminal.compareString(str2)) {
      int chk = DHT.read11(dht);
      Terminal.println(DHT.humidity);
      Terminal.println("%");
    }
    else if (Terminal.compareString(str3)) {
      int lightValue = analogRead(LDR);
      Terminal.println("Light Value: ");
      if (lightValue >= 900) {
        Terminal.println("High");
      }
      else if (lightValue <= 899 && lightValue >= 880) {
        Terminal.println("Medium");
      }
      else {
        Terminal.println("Low");
      }
    }
  }
}

void liftDetection()
{
  rightRead = digitalRead(RIGHT);
  middleRead = digitalRead(MIDDLE);
  leftRead = digitalRead(LEFT);

  if (rightRead == 1 || middleRead == 1 || leftRead == 1) { //on ground
    wheelsState = HIGH;
  }
  if (rightRead == 0 && middleRead == 0 && leftRead == 0) { //off ground
    wheelsState = LOW;
4  }
}


void obstactleDetection() {
  front1Read = digitalRead(FRONT1);
  front2Read = digitalRead(FRONT2);
  back1Read = digitalRead(BACK1);
  back2Read = digitalRead(BACK2);

  if (front1Read == HIGH || front2Read == HIGH || back1Read == HIGH || back2Read == HIGH) {
    sr.set(ENA, LOW);
    sr.set(N1, LOW);
    sr.set(N2, LOW);
    sr.set(ENB, LOW);
    sr.set(N3, LOW);
    sr.set(N4, LOW);
  }
}
void loop() {
  Dabble.processInput();

  obstactleDetection();
  liftDetection();
  buttonRead();
  sensorReadings();
  headLights();
}