Sistem Digital Line Follower (Processing) With Bluetooth

#include <LiquidCrystal_SR_LCD3.h>
const int PIN_LCD_STROBE  = 2;
const int PIN_LCD_DATA  = 3;
const int PIN_LCD_CLOCK = 4;
LiquidCrystal_SR_LCD3 lcd(PIN_LCD_DATA, PIN_LCD_CLOCK, PIN_LCD_STROBE);

/* MOTOR */
int mt1=5, mt2=6, mt3=12, mt4=8;
#define enA NULL
#define in1 8
#define in2 6
#define enB NULL
#define in3 12
#define in4 5

int motorSpeedA = 0;
int motorSpeedB = 0;
/* BUTTON SW3 SW4 SW5 SW6*/
int sw3=8, sw4=13, sw5=11, sw6=12;
/* END BUTTON */

void setup() {
  Serial.begin(9600);

  lcd.clear();

  pinMode(7, OUTPUT);
  /* BUTTON */
  //pinMode(sw3, INPUT);
  pinMode(sw4, INPUT);
  pinMode(sw5, INPUT);
  //pinMode(sw6, INPUT);
  /* END BUTTON */

  /* MOTOR */
  pinMode(enA, OUTPUT);
  pinMode(enB, OUTPUT);
  pinMode(in1, OUTPUT);
  pinMode(in2, OUTPUT);
  pinMode(in3, OUTPUT);
  pinMode(in4, OUTPUT);
  /* END MOTOR */

  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }
  lcd.begin(16, 2);
  lcd.home();
  lcd.setCursor(4,0);
  lcd.print("*Welcome*"); delay(1000);
  lcd.clear();
  lcd.setCursor(1,0);
  lcd.print("Line  Follower");
  lcd.setCursor(6,1);
  lcd.print("v1.0");
  delay(3000);
  lcd.clear();
}

int kecepatan = 100;

void loop() {
  if(Serial.available()){
    digitalWrite(7, HIGH);
    char controllRobo = Serial.read();
    lcd.setCursor(0,0);
    lcd.print(controllRobo);
    if(controllRobo == '8'){
      fmotorpwm(kecepatan, kecepatan);
      Serial.println("Forward");
    }else if(controllRobo == '5'){
      smotor();
      Serial.println("STOP!");
      digitalWrite(7, LOW);
    }else if(controllRobo == '2'){
      bmotor();
      Serial.println("Back");
      digitalWrite(7, LOW);
    }else if(controllRobo == '4'){
      //Speed-
      if(kecepatan > 5 && kecepatan <= 255){
        kecepatan -= 5;
      }
      lcd.clear();
      lcd.setCursor(0,1);
      lcd.print(kecepatan);
      Serial.println(kecepatan);
    }else if(controllRobo == '6'){
      //Speed+
      if(kecepatan >= 0 && kecepatan < 250){
        kecepatan += 5;
      }
      lcd.clear();
      lcd.setCursor(0,1);
      lcd.print(kecepatan);
      Serial.println(kecepatan);
    }
  }
}


void fmotor(){
  analogWrite(in2, 255);
  analogWrite(in4, 255);
}

void bmotor(){
  digitalWrite(in1, HIGH);
  digitalWrite(in3, HIGH);
}

void smotor(){
  digitalWrite(in1, LOW);
  digitalWrite(in3, LOW);
  analogWrite(in2, 0);
  analogWrite(in4, 0);
}

void fmotorpwm(int motora, int motorb){
  analogWrite(in2, motora);
  analogWrite(in4, motorb);
}