int speed = 255;

void setup() {
  Serial.begin(9600);
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);
}

void loop() {

  ZaStav();
}

void PoSmeru(int motor, int rychlost) {
  if(motor == 0) {
    digitalWrite(2, HIGH);
    analogWrite(3, rychlost);
    analogWrite(4, 0);
  }
  if(motor == 1) {
    digitalWrite(7, HIGH);
    analogWrite(5, rychlost);
    analogWrite(6, 0);
  }
}

void ProtiSmeru(int motor, int rychlost) {
  if(motor == 0) {
    digitalWrite(2, HIGH);
    analogWrite(3, 0);
    analogWrite(4, rychlost);
  }
  if(motor == 1) {
    digitalWrite(7, HIGH);
    analogWrite(5, 0);
    analogWrite(6, rychlost);
  }
}

void NeToc(int motor) {
  if(motor == 0) {
    digitalWrite(2, LOW);
    analogWrite(3, 0);
    analogWrite(4, 0);
  }
  if(motor == 1) {
    digitalWrite(7, LOW);
    analogWrite(5, 0);
    analogWrite(6, 0);
  }
}

void DoPredu() {
  PoSmeru(0, speed);
  ProtiSmeru(1, speed);
}

void DoZadu() {
  ProtiSmeru(0, speed);
  PoSmeru(1, speed);
}

void DoPrava() {
  PoSmeru(0, speed);
  PoSmeru(1, speed);
}

void DoLeva() {
  ProtiSmeru(0, speed);
  ProtiSmeru(1, speed);
}

void ZaStav() {
  NeToc(0);
  NeToc(1);
}