#define PWM_A_PIN 5
#define PWM_B_PIN 10
#define IN_A_PIN  6
#define IN_B_PIN  9

#define R_BASE 100
#define L_BASE 50

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

  pinMode(5,OUTPUT);
  pinMode(6,OUTPUT);
  pinMode(9,OUTPUT);
  pinMode(10,OUTPUT);
}

void loop(){
  turn('l', constrain(L_BASE + speedUpdate, -L_BASE, L_BASE));
  turn('r', constrain(R_BASE - speedUpdate, -R_BASE, R_BASE));
}

void turn(char direction, int16_t speed){
  // Serial.println(String(direction)+" "+String(speed));
  bool speedNegative = (speed < 0);
  if (direction == 'l'){
    analogWrite(PWM_A_PIN, speedNegative*255 + speed);
    digitalWrite(IN_A_PIN, speedNegative);
  } else
  if (direction == 'r'){
    analogWrite(PWM_B_PIN, speedNegative*255 + speed);
    digitalWrite(IN_B_PIN, speedNegative);
  }  
}