CODE for master Arduino

int m1a = 9;
int m1b = 10;
int m2a = 11;
int m2b = 12;
int LED1 = 2;
int SER_1 = 3;
int M_A  = 4;
int M_B  = 5;
char val;

void setup() 
{ 
pinMode(m1a, OUTPUT);  
pinMode(m1b, OUTPUT);  
pinMode(m2a, OUTPUT);  
pinMode(m2b, OUTPUT);  
pinMode(LED1,OUTPUT);  
pinMode(SER_1,OUTPUT);  
pinMode(M_A,OUTPUT);   
pinMode(M_B,OUTPUT);  
Serial.begin(9600);
}

void loop()
{
  
  
  while (Serial.available() > 0)
  {
  val = Serial.read();
  Serial.println(val);
  }

  if( val == 'F') // Forward
    {
      digitalWrite(m1a, LOW);
      digitalWrite(m1b, HIGH);
      digitalWrite(m2a, HIGH);
      digitalWrite(m2b, LOW);  
    }
  else if(val == 'B') // Backward
    {
      digitalWrite(m1a, HIGH);
      digitalWrite(m1b, LOW);
      digitalWrite(m2a, LOW);
      digitalWrite(m2b, HIGH); 
    }
  
    else if(val == 'L') //Left
    {
    digitalWrite(m1a, LOW);
    digitalWrite(m1b, LOW);
    digitalWrite(m2a, HIGH);
    digitalWrite(m2b, LOW);
    }
    else if(val == 'R') //Right
    {
    digitalWrite(m1a, LOW);
    digitalWrite(m1b, HIGH);
    digitalWrite(m2a, LOW);
    digitalWrite(m2b, LOW); 
    }
    
  else if(val == 'S') //Stop
    {
    digitalWrite(m1a, LOW);
    digitalWrite(m1b, LOW);
    digitalWrite(m2a, LOW);
    digitalWrite(m2b, LOW); 
    }
  else if(val == 'I') //Forward Right
    {
    digitalWrite(m1a, HIGH);
    digitalWrite(m1b, LOW);
    digitalWrite(m2a, LOW);
    digitalWrite(m2b, LOW);
    }
  else if(val == 'J') //Backward Right
    {
    digitalWrite(m1a, LOW);
    digitalWrite(m1b, HIGH);
    digitalWrite(m2a, LOW);
    digitalWrite(m2b, LOW);
    }
   else if(val == 'G') //Forward Left
    {
    digitalWrite(m1a, LOW);
    digitalWrite(m1b, LOW);
    digitalWrite(m2a, HIGH);
    digitalWrite(m2b, LOW);
    }
  else if(val == 'H') //Backward Left
    {
    digitalWrite(m1a, LOW);
    digitalWrite(m1b, LOW);
    digitalWrite(m2a, LOW);
    digitalWrite(m2b, HIGH); 
    }
    else if(val == 'W')
    {
      digitalWrite(LED1, HIGH);
       
    }
    else if(val == 'w') 
    {
      digitalWrite(LED1, LOW);
       
    }
     else if(val == 'X') 
    {
      digitalWrite(SER_1, HIGH);
    }
    else if(val == 'x') 
    {
       digitalWrite(SER_1, LOW);             
                                       
    }
     else if(val == 'V')
    {
      digitalWrite(M_A, HIGH);
      digitalWrite(M_B, LOW);
       
    }
    else if(val == 'v') 
    {
      digitalWrite(M_A, LOW);
      digitalWrite(M_B, LOW);
    }  
   
 }