const int ledPin12 = 12;

int rychlost = 40;

const int analogPin = A0;

void setup() {
  pinMode(ledPin12, OUTPUT);
  pinMode(analogPin, INPUT);
  Serial.begin(9600);
}

void loop() {
int value;

value = analogRead(analogPin);
value = map(value, 0, 1023, 0, 255);

analogWrite(ledPin12, value);

Serial.println(value);
}