class Generator
{
  int prodleva, status, f;
  double cas;
public:
  Generator(): status(0), cas(0), f(10), prodleva(100) {}
  void tick()
  {
    cas += prodleva/1000.;
    if (status)
    {
      Serial.print(cas);
      Serial.print(" ");
      Serial.print(sin(6.28*cas));
      Serial.println(";");
    }
    delay(prodleva);
  }
  void start() {status = 1;}
  void stop() {status = 0;}
  void reset() {cas = 0;}
  void setFR(int fr) {f = fr;}
  void setSR(int sr) {prodleva = 1000/sr;}
};

void setup() {
  Serial.begin(115200);
}

Generator g;

void loop() {
  if(Serial.available())
  {
    String cmd = Serial.readStringUntil('\n');
    int ind = cmd.indexOf('=');
    if (ind > 0)
    {
      String cmd1 = cmd.substring(0, ind);
      int value = cmd.substring(ind+1).toInt();

      if (cmd1 == "fvz")
        g.setSR(value);
      else if (cmd1 == "fper") 
        g.setFR(value);
    }
    if (cmd == "start")
      g.start();
    else if (cmd == "stop") 
      g.stop();
    else if (cmd == "tim_rst")
      g.reset();
  }
  g.tick();  
}