Pygame USB-serial control - Arduino receiver end

// MrLunk's Autonomous Vehikel 2017 - Serial motion control

#include <Servo.h>
#include <Wire.h>

Servo myservo;

// const int led = 13;
int usbRead =0;

Servo SteeringServo;
int MaxSteerAngle = 30;
int Speed = 100;
int MaxSpeed = 60;

int RPWM_Output = 5; // Arduino PWM output pin 5; connect to IBT-2 pin 1 (RPWM)
int LPWM_Output = 6; // Arduino PWM output pin 6; connect to IBT-2 pin 2 (LPWM)

// --------------------------------------------------------------

void setup() {

  Serial.begin(9600);
  // pinMode(led, OUTPUT);
  // digitalWrite(led, LOW);

  pinMode(RPWM_Output, OUTPUT);
  pinMode(LPWM_Output, OUTPUT);

  SteeringServo.attach(7);
}

// --------------------------------------------------------------

void loop() {
  if(Serial.available()) {

    usbRead = Serial.read() - '0';
    Serial.println(usbRead);

    if(usbRead == 8) {
      Forwards();
      usbRead = 0;
    }

    if(usbRead == 7) {
      StopEngine();
      usbRead = 0;
    }

    if(usbRead == 5) {
      SteerStraight();
      usbRead = 0;
    }

    if(usbRead == 2) {
      Backwards();
      usbRead = 0;
    }

    if(usbRead == 4) {
      SteerRight();
      usbRead = 0;
    }

    if(usbRead == 6) {
      SteerLeft();
      usbRead = 0;
    }


  }
}

// --------------Routine definitions------------------------------

void Forwards(){
  analogWrite(LPWM_Output, 0);
  analogWrite(RPWM_Output, MaxSpeed);
  // delay(200);

}

void SteerStraight(){
  SteeringServo.write(90);
}

void StopEngine(){
  analogWrite(LPWM_Output, 0);
  analogWrite(RPWM_Output, 0);
}

void Backwards(){
  analogWrite(LPWM_Output, MaxSpeed);          // Backwards
  analogWrite(RPWM_Output, 0);
  // delay(200);
}

void SteerRight(){
  SteeringServo.write(90 - MaxSteerAngle);

}

void SteerLeft(){
  SteeringServo.write(90 + MaxSteerAngle);
}